Electronic Circuit Directory

Optimization of Heat Sink Design

2010-03-22T04:11:00.000-07:00

Economic Optimization of Heat Sink Design

INTRODUCTION

This paper describes the analysis and derivation of an optimum heat

sink design for maximizing the thermoelectric cooling performance

of a laboratory liquid chiller. The methods employed consisted of

certain key changes in the design of the heat sink in order to improve

its thermal performance. Parametric studies were performed in order

to determine the optimized cooling system design per dollar."

"The objective of this project was to analyze the thermal performance

of an initial simple heat sink design and improve cooling

performance while reducing the cost and overall size of the cooling

system. Several changes were examined in an effort to improve the

thermal performance and/or to reduce overall cost. The result

obtained has provided some guidelines for the selection/design of the

most effective and economical heat sink configuration. These results

were somewhat surprising since they are contrary to what one might

instinctively expect without the benefit of the detailed analysis

presented in this paper.

Optimization of Heat Sink Design and Fan Selection in Portable Electronics Environment

Abstract

Modern portable electronics have seen component heat loads

increasing, while the space available for heat dissipation has

decreased, both factors working against the thermal designer.

This requires that the thermal management system be optimized

to attain the highest performance in the given space. While

adding fins to the heat sink increases surface area, it also

increases the pressure drop. This reduces the volumetric airflow,

which also reduces the heat transfer coefficient. There exists a

point at which the number of fins in a given area can be optimized

to obtain the highest performance for a given fan. The primary

goal of this paper is to find the optimization points for several

different fan-heat sink designs. The secondary goal is to find a

theoretical methodology that will accurately predict the

optimization point and the expected performance.

HOW TO CALCULATE AND SELECT A Electronic Circuit HEAT SINK

2010-03-20T04:08:00.000-07:00

HOW TO CALCULATE AND SELECT A HEAT SINK FOR A GIVEN SOLID STATE RELAY APPLICATION

The basic structure of a Solid State Relay includes an internal power semiconductor mounted to an electrical insulator which in turn is mounted to the Solid State Relay’s base plate. To form an assembly, the SSR with an accompanying thermal interface material placed on its base plate is then torque mounted to the Heat Sink.

The thermal model representing the above configuration includes the following elements:

The selected SSR with specified thermal impedance (RΘ ssr), forward voltage drop (Vf), and maximum allowed internal operating temperature (Tj).

The thermal interface material placed between the SSR and the Heat Sink and its specified thermal impedance (RΘ tp).

The calculated minimum Heat Sink thermal impedance rating (RΘ hs) required for proper SSR operation.

The operating environment’s max ambient air temperature in °C (TA ).

How to verify the proper Heat Sink

In certain instances, once the heat sink requirements for a SSR in a particular application have been determined and installed, it may be desirable to verify that the system does indeed provide adequate cooling to ensure reliable SSR operation.

The following is a relatively simple method to check this suitability, and essentially uses some of the calculations from SELECTING A SUITABLE HEAT SINK (above) in a reverse manner. This technique may also be used on existing systems in the field that might have been more or less “empirically” designed, to gain information on their performance and potential reliabilty. This method involves determining the temperature of the internal power devices

Electronic Circuit Heat Sink Selection

2010-03-18T04:04:00.000-07:00

Heat Sink Selection For Solid State Relay Applications

ABSTRACT

Heat Sinks are required to insure the proper operation and long term reliability of Solid State Relays because they provide a means to dissipate the power that is normally developed by the SSR into the surrounding ambient air and maintain a safe operating temperature. Selecting the correct Heat Sink for any given SSR application involves coordinating form factor, size, mounting and thermal impedance rating. This paper discusses “Why Heat Sinks are Required for Reliable Solid State Relay Operation”, how the minimum required Heat Sink thermal impedance rating is calculated based upon application operating conditions, and includes an example calculation.

Selecting a Suitable Electronic Circuit Heatsink

Due to the forward voltage drop of the output SCRs, solid state relays generate an internal power loss. The amount of power generated is afunction of the load current. The manufacturer provides power loss curves, as shown in Fig 1. At normal load currents the power loss can be estimated at 1 Watt for every 1 Arms of load current. In order to maintain an acceptable power switch junction temperature, some form of

heatsink must dissipate the heat generated by the power loss. For most printed circuit board types, the relay current rating is established by measuring the thermal impedance, from the dissipating elements to air, using the relay package as the heat sink. Some printed circuit board types are available with an integral heatsink; their ratings reflect the additional effects of the integral heatsink.

Basic Thermal Equation and Heat Transfer

2010-03-16T04:01:00.000-07:00

Thermal Equation Parameters

Many parameters contribute to a design's thermal circuit, including the

device's maximum power consumption for the design, the maximum

environment temperature, package characteristics, and airflow at the

device.

Maximum Power Consumption (P)

Use the power calculator values from design simulations in the Altera

Quartus® II software (or the device's power calculator at

http://www.altera.com) to estimate the maximum power consumption

of the device. Once a prototype design is available, measure the actual

power consumption and use this value for thermal calculations.

Maximum Temperature (TJ & TA)

The maximum ambient and junction temperatures are found in the data

sheet for the device under Device Absolute Maximum Rating and the

operating junction temperature is found under Device Recommended

Operating Conditions. The temperature must be kept within the

maximum conditions or damage could occur. The junction temperature

should be kept within the recommended operating conditions to ensure

the device achieves the performance reported by the Quartus II software.

HEAT TRANSFER Basic Theory

The rate at which heat is conducted

through a material is proportional

to the area normal to the heat flow

and to the temperature gradient

along the heat flow path. For a one

dimensional, steady state heat flow

the rate is expressed by Fourier’s

equation:

Basic HEAT TRANSFER FUNDAMENTALS and Heatsink

2010-03-14T03:54:00.000-07:00

HEATSINK BASICS

All semiconductor devices have some electrical resistance, just

like resistors and coils, etc. This means that when power

diodes, power transistors and power MOSFETs are switching

or otherwise controlling reasonable currents, they dissipate

power as heat energy. If the device is not to be damaged by

this, the heat must be removed from inside the device

(usually the collector-base junction for a bipolar transistor, or

the drain-source channel in a MOSFET) at a fast enough rate

to prevent excessive temperature rise. The most common way

to do this is by using a heatsink.

To understand how heatsinks work, think of heat energy itself

as behaving very much like an electrical current, and

temperature rise as the thermal equivalent of voltage drop. We

also have to introduce a property of materials and objects

known as thermal resistance, which behaves in a very similar

way to electrical resistance: the more heat energy flowing

through it, the higher the temperature rise across it. As you

might imagine metals like copper and aluminium have very low

thermal resistance, while air tends to have a relatively high

resistance. So do many plastics and ceramic materials.

HEAT TRANSFER FUNDAMENTALS

Introduction

The objective of thermal management programs in electronic packaging is the efficient removal of heat from the semiconductor junction to the ambient environment. This process can be separated into three major phases:

1) heat transfer within the semiconductor component package;

2) heat transfer from the package to a heat dissipater (the initial heat sink);

3) heat transfer from the heat dissipater to the ambient environment (the ultimate heat sink)

Heatsink

Thermal Management Using Heat Sinks and Effects of Heat on Electronic Circuits and Devices

2010-03-12T03:53:00.000-08:00

The Effects of Heat on Electronic Circuits and Devices

Charles Nogales, VP of Engineering at Emulex, talks about the effects of heat on electronic circuits and devices, such as HBAs, and how heatsinks play a role in keeping networking and server product

Thermal Management Using Heat Sinks

Thermal management is an important design consideration with complex

devices running at high speeds and power levels as these devices can

generate significant heat. Proper thermal management can increase

product performance and life expectancy. The thermal management

requirements for a programmable device depend on its application.

AlteraR packages are designed to minimize thermal resistance

characteristics and maximize heat dissipation. However, in some cases,

complex designs require heat dissipation greater than packages provide.

This application note discusses ways to dissipate heat, how to calculate

the heat dissipation of a device, and how to determine if a device requires

a heat sink in an application.

AC Line Current Detector Circuit

2009-12-05T05:32:00.001-08:00

AC Line Current Detector
This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line. Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #30 - #35 magnet wire. The pickup could be made from other iron type rings or transformer cores that allows enough space to pass one of the AC lines through the center. Only one of the current carrying lines, either the line or the neutral should be put through the center of the pickup to avoid the fields cancelling. I tested the circuit using a 2 wire extension cord which I had separated the twin wires a small distance with an exacto knife to allow the U-bolt to encircle only one wire.

more

A Unique Discrete Zero-Crossing Detector
A zero-crossing detector delivers an output pulse that synchronizes other circuitry to the transitions through zero volts of a sinusodial source for both polarity excursions. This detector, which was developed to operate from the ac power line, includes a unique negative-voltage detector/level shifter

more

AC Line Sensing – Zero-Crossing Detector

The circuit I came up with is very inexpensive and works as follows. The AC line goes through some resistors to limit the current. The resistors are shown as two parts in parallel, but this is just to split the power between them since they may get a bit warm. The AC voltage goes into a bridge rectifier.

more

AC Current Indicator Light Circuit

This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts. It will turn on a LED light whenever current is being drawn by a load. It is especially useful for remote lights, where you may not be able to see if the lamps are receiving power.

more

Method and system for line current detection for power line cords

spects for detecting current flow in a power line cord are described. In these aspects, a line current detector circuit is provided for each input plug line of a power distribution box. A determination of whether line current is flowing in a system line cord plugged into the power distribution box is based on a light indicator from the line detector circuit. The line current detector circuit includes a magnetic device for detecting line current flowing in a power line cord, and a light emitting diode (LED) coupled to the magnetic device for outputting a light indicative of whether current is flowing in the power line cord.

more

Isolation Triac Driver Circuit

2009-11-13T01:04:00.000-08:00

Isolation Triac Driver Circuit - Resistive Load

Isolation Triac Driver Circuit - Inductive Load with Sensitive Gate Triac (IGT ≤15 mA)

Isolation Triac Driver Circuit - the “hot” side of the line is switched and the load connected to the cold or ground side.

OPTOISOLATORS TRIAC DRIVER OUTPUT
DESCRIPTION
The MOC301XM and MOC302XM series are optically
isolated triac driver devices. These devices contain a
AlGaAs infrared emitting diode and a light activated silicon
bilateral switch, which functions like a triac. They
are designed for interfacing between electronic controls
and power triacs to control resistive and inductive loads
for 115/240 VAC operations.

FEATURES
• Excellent IFT stability IR emitting diode has low degradation
• High isolation voltage minimum 5300 VAC RMS
• Underwriters Laboratory (UL) recognizedFile #E90700
• Peak blocking voltage
-250V-MOC301XM
-400V-MOC302XM
• VDE recognized
-Ordering option V

SD/MMC Card interfacing with Microcontroller Circuit Project

2009-07-28T06:12:00.000-07:00

SD/MMC Card interfacing with MUC with AVR Microcontrollers
Interfacing with ATMega 162:

It is easy to interface a MMC (Multimedia Card) with an Atmel ATmega162 (AVR series) via the SPI (Serial Port Interface). The MMC is connected to the SPI pins of the ATmega16 via simple resistor voltage dividers to transform the +5V high levels to about 3.3V used by the MMC. If the Atmega-162 is working on 3.3 V power supply then all the MMC pins can be directly connected to Microcontroller (as in this design). The data-out pin from the MMC goes directly to the ATmega162, because 3.3V is high for the ATmega162 anyway. The schematic of the MMC interfacing is given below.

http://devusb.googlepages.com/sdmmcinterfacing

Microcontroller board with Ethernet, MMC/SD card interface and USB
Hardware components already integrated on the reference design include:
• Atmel ATmega128 RISC microcontroller with standard 10-pin ISP header
• 64 kByte of external SRAM
• USB <-> RS232 interface
• SD/MMC socket
• Ethernet interface with ENC28J60 (IEEE 802.3, 10Base-T)
The hardware design is expandable by connecting additional components to the existing pin header. Several digitial I/Os, A/D inputs as well as the standard SPI and I2C (TWI) serial interfaces are available for user-defined purposes.
The curcuit board is designed as a two-layer board of size 100mm x 80mm. Most components use SMD packages.

http://www.roland-riegel.de/mega-eth/index.html

SD/MMC Interface Integration Guidelines
SD/MMC cards provide a low cost solution for data logging and storage applications
for embedded systems. SD/MMC cards can be easily interfaced with a
Microcontroller using an SPI interface and between one and three control lines. While
the electrical interface is relatively straight forward, successfully implementing a
solution can be time consuming for the initial implementation. This document looks at
some of the common pitfalls encountered. The document assumes the developer is
implementing Brush Electronics SD/MMC File System drivers or Utilities with a
Microchip PIC Microcontroller however the principles apply to other implementations.

http://www.smallridge.com.au/download/SD-MMC%20Integration.pdf

MMC/SD Card interfacing and FAT16 Filesystem with 8051/8052

Content

# Interface to Chan’s Library of functions

# Target development platform

# Setting up the SPI port during startup.A51

# Global type definitions and variables

# Basic SPI function

1. Transferring & Receiving single byte over SPI Bus
2. SPI Chip Select
3. Setting frequency for SPI Clock
4. Sending command to SD Card
5. Reading response from SD Card
6. Delay and Time function

# SD Card Initialization

1. Setting up the card for SPI Communication

# Reading and Writing a single sector

# Working with diskio.c

# Pulling it all together

http://www.8051projects.net/mmc-sd-interface-fat16/MMC-SD-Card-interfacing-and-FAT16-Filesystem.pdf

H-Bridge Motor Driver Circuit

2009-07-18T00:31:00.000-07:00

H-Bridge
This circuit drives small DC motors up to about 100 watts or 5 amps or 40 volts, whichever comes first. Using bigger parts could make it more powerful. Using a real H-bridge IC makes sense for this size of motor, but hobbyists love to do it themselves, and I thought it was about time to show a tested H-bridge motor driver that didn't use exotic parts.

http://www.bobblick.com/techref/projects/hbridge/hbridge.html

H-bridge using P and N channel FETs
This H-bridge uses MOSFETs for one main reason - to improve the efficiency of the bridge. When BJT transistors (normal transistors) were used, they had a saturation voltage of approximately 1V across the collector emitter junction when turned on. My power supply was 10V and I was consuming 2V across the two transistor required to control the direction of the motor. 20% of my power was eaten up by the transistors. I tried darlingtons etc... nothing worked. The transistors also would get quite hot - no room for heatsinks.

http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-bridge.htm

N-Channel H-bridge Motor Drive
In low voltage motor drives, it is common practice to use
complementary MOSFET half-bridges to simplify the gate
drive design. However, the P-channel FET within the
half-bridge usually has a higher on resistance or is larger
and more expensive than the N-channel FET. The alternative
solution is to design in an N-channel half-bridge.

http://www.eetkorea.com/ARTICLES/2004MAY/2004MAY18_BD_MSD_PD_AN.PDF

Comparator Controlled H-Bridge Circuits (LM311)
The next two circuits are simple Bi-Polar H-Bridge circuits. The bridges are controlled by a pair of LM311 voltage Comparators.
The LM311 Voltage Comparator has several unique features, one of which is an output transistor with an open emitter as well as the typical open collector. This allows the output transistor of the comparator to sit between the bases of the power transistors.

http://home.cogeco.ca/~rpaisley4/HBridge.html

Robot Motor control
In order to control the speed/torque of a motor, a so called H-bridge can be used. I built/designed one myself, using 4 MOSFETs.

http://www.iwhat.nl/rienatmarobi/bots/Wheeley/motor/index.html

Bidirectional operation (H-bridge circuit)
We have achieved speed control and have made a powerful drive circuit. However in robotic work we also usually want to be able to drive a motor either clockwise or counterclockwise. Before we discuss the use of transistors to solve this problem

http://www.mech.uwa.edu.au/NWS/How_to_do_stuff/micro_crash_course/pwm/

DC Motor Speed Control Circuit

2009-07-11T01:52:00.001-07:00

Speed Controller Circuit
The robot I intend to build will be a 4WD bot with a skid steer system so to do this best I have opted to build 2 a controller system moulded around a 4QD DCI111. (A DCI111 converts radio signals into useable signals) Because of this the inputs on my controllers have to be similar to the 4QD units. The next things to consider are the motors that I will be using. Bosch 750’s seem to be quite popular (so are ford escorts and they are crap) so I will just go ahed and use the many starter motors that I have lying around. This results in

more

DC Motor Control & Interfacing Circuit
A permanent magnet DC motor responds to both voltage and current. The steady state voltage across a motor determines the motor’s running speed, and the current through its armature windings determines the torque. Apply a voltage and the motor will start running in one direction; reverse the polarity and the direction will be reversed. If you apply a load to the motor shaft, it will draw more current, if the power supply does not able to provide enough current, the voltage will drop and the speed of the motor will be reduced. However, if the power supply can maintain voltage while supplying the current, the motor will run at the same speed. In general, you can control the speed by applying the appropriate voltage, while torque is controlled by current. In most cases, DC motors are powered up by using fixed DC power supply, therefore; it is more efficient to use a chopping circuit.

more

PWM D.C. motor drive Circuit
This circuit is a very compact switching regulator for small DC motors. I use it for my small printed circuit board drill (18 Volt, 1.5 Amp), but it is suitable for many other applications (e.g. 12V DC halogen dimmer).

more

Back EMF PM Motor Speed Control Circuit

A 12 V control supply and a TRW BL11, 30 V motor are used; with minor changes other motor and control voltages can be accommodated. For example, a single 24 V rail could supply both control and motor voltages. Motor and control voltages are kept separate here because CMOS logic is used to start, stop, reverse and oscillate the motor with a variable delay between motor reversals.
more

Bidirectional DC Motor Speed Controller
This kit allows controlling the speed of a DC motor in
both the forward and reverse direction. The range of
control is from fully OFF to fully ON in both directions.

This kit overcomes both these problems. The direction and
speed is controlled using a single potentiometer. Turning
the pot in one direction causes the motor to start spinning.
Turning the pot in the other direction causes the motor to
spin in the opposite direction. The center position on the
pot is OFF, forcing the motor to slow and stop before
changing direction.

more pdf

PWM DC Motor Speed Control

The left half of the 556 dual timer IC is used as a fixed frequency square wave oscillator. The oscillator signal is fed into the right half of the 556 which is configured as a variable pulse width one-shot monostable multivibrator (pulse stretcher).
more

DC Motor Controlled with PWM Resources
Here is a description of the driver circuit. It's based on the Microchip AN531 Application Note titled "Remote Positionner". The circuit given in the application Note do not work , so this is a correction of the circuit:

more

DC MOTOR CONTROL USING A SINGLE SWITCH
This simple circuit lets you run a DC motor in clockwise or anti-clockwise
direction and stop it using a single switch. It provides a constant voltage for
proper operation of the motor. The glowing of LED1 through LED3 indicates that
the motor is in stop, forward rotation and reverse conditions, respectively.

more pdf

Bidirectional DC motor speed control using Pulse Width Modulation
The simplest method of implementing microcontroller controlled H-bridge drive of a reversible DC motor is to buy one of many commercial H-bridge IC's availible on the market. These can be purchased separately as an H-Bridge with a separate H-Bridge controller IC, or as an all-in-one IC. Unfortunately, there are several hurdles that sometimes frustrate this approach. Students often find these devices hard to find, as they are apparently in high demand. Secondly, many of these devices have limited current drive ability, such that larger DC motors end up running sluggish or stalling easily. One option is to build your own H-bridge from discrete parts, as shown below.

more

Low-Cost DC Motor Speed Control with CMOS ICs
Two low-cost CMOS ICs manage a 12 VDC, current-limited speed
control circuit for DC brush motors. The circuit design (see
Figure 1) uses PWM (pulse width modulation) to chop the effective
input voltage to the motor. Use of CMOS devices gives the benefits
of low power, minimal heat and improved longevity. The overall
design is simple, inexpensive and reliable, and is useful in applications
such as embedded DC motor control where efficiency,
economy and performance are essential.

more pdf

Digital Speed Control by Anthony Psaila
My design is based around three parts:
1. The controller board. This is a fully digital circuit that takes the 1ms to 2ms pulse from the receiver and converts it into a pwm train at 1Khz. It uses six cmos ics (74hc and 40 series) and a 4Mhz crystal clock. The only other components are one resistor and two capacitors to complete the crystal clock and a capacitor across the supply for smoothing. This was built on a printed board measuring 2 x 2.25 inches using standard components (on the boat there was no shortage of space). If surface mounted devices are used, the lot can be crammed into a much smaller space. The circuit can give a resolution of 128 steps (7bits). Some day I will expand it to have reverse function, but this is better done by a switcher circuit supplied from another channel (my reciever can give 7 channels and I am using only two at present).

more

Brushless DC Motors Theory and Driver Circuit

2009-07-03T02:11:00.000-07:00

Why use brushless DC motors (advantages/disadvantages)?
Brushless DC motors are synchronous motors suitable for use as a simple means of controlling permanent drives (e.g. ABS pumps, EHPS pumps, fuel pumps or cooling fans). This type of 3-, 4- or 5-phase brushless DC motor will increasingly replace brushed DC motors. Brushed DC motors require maintenance, e.g. to service coal brushes and commutator. Another major problem with a brushed DC machine is the possibility of brush burnout in the event of an overload or stall condition.

Functional principle of a brushless DC motor
Figure 1 shows a three-phase brushless DC motor with two pole pairs. The rotation of the electrical field (vector) has to be applied twice as fast as the desired mechanical speed of the brushless DC motor. The three coils of the stator are split into two groups of coils (A, B, C and A’, B’, C’). As you can see in Figure 1, coils A and C are energized and coil B is not energized. A 0° to 180° rotation will be shown in detail in section 2.1 to explain the setting of the appropriate switches of the B6 bridge pattern, the appropriate voltages relating to the coils, and the energized coils of the motor with the suitable rotor position between 0° and 180° mechanical.

Brushless DC Motors wiring diagrams
The wiring diagrams for a 3-pole armature (stator) Brushless DC Motors

The wiring diagrams for a 6-pole armature Brushless DC Motors

more

Brushless DC Motors Animation
Brushless DC motors are refered to by many aliases: brushless permanent magnet, permanent magnet ac motors, permanent magnet synchronous motors ect. The confusion arises because a brushless dc motor does not directly operate off a dc voltage source. However, as we shall see, the basic principle of operation is similar to a dc motor.

more

Introduction to Brushless DC Motors
Brushless Motor Construction
DC brushless motors are similar in performance and application to brush-type DC motors. Both have a speed vs. torque curve which is linear or nearly linear. The motors differ, however, in construction and method of commutation. A brush-type permanent magnet DC motor usually consists of an outer permanent magnet field and an inner rotating armature. A mechanical arrangement of commutator bars and brushes switches the current in the armature windings to maintain rotation. A DC brushless motor has a wound stator, a permanent magnet rotor assembly, and internal or external devices to sense rotor position. The sensing devices provide signals for electronically switching (commutating) the stator windings in the proper sequence to maintain rotation of the magnet assembly. The rotor assembly may be internal or external to the stator in a DC brushless motor. The combination of an inner permanent magnet rotor and outer windings offers the advantages of lower rotor inertia and more efficient heat dissipation than DC brush-type construction. The elimination of brushes reduces maintenance, increases life and reliability, and reduces noise and EMI generation.
DC Brushless Motor Control Block Diagram

more

Brushless DC Motor driver circuit

Closed Loop Brushless DC Motor Control With the MC33033 Using the MC33039 driver circuit

The MC33033 is a high performance second generation, limited
feature, monolithic brushless dc motor controller which has evolved
from ON Semiconductor's full featured MC33034 and MC33035
controllers. It contains all of the active functions required for the
implementation of open loop, three or four phase motor control. The
device consists of a rotor position decoder for proper commutation
sequencing, temperature compensated reference capable of supplying
sensor power, frequency programmable sawtooth oscillator, fully
accessible error amplifier, pulse width modulator comparator, three
open collector top drivers, and three high current totem pole bottom
drivers ideally suited for driving power MOSFETs. Unlike its
predecessors, it does not feature separate drive circuit supply and
ground pins, brake input, or fault output signal.

more pdf

THREE-PHASE BRUSHLESS DC MOTOR driver circuit

The L6235 is a DMOS Fully Integrated Three-Phase
Motor Driver with Overcurrent Protection.
Realized in MultiPower-BCD technology, the device
combines isolated DMOS Power Transistors with
CMOS and bipolar circuits on the same chip.
The device includes all the circuitry needed to drive a
three-phase BLDC motor including: a three-phase
DMOS Bridge, a constant off time PWM Current Controller
and the decoding logic for single ended hall
sensors that generates the required sequence for the
power stage.

more pdf

3-Phase Full-Wave PWM Driver for Sensorless brushless Motors driver circuit
The TB6588FG is a three-phase full-wave PWM driver for
sensorless brushless DC (BLDC) motors. It controls rotation speed
by changing the PWM duty cycle, based on the voltage of an
analog control input.

more pdf

Microstepping Stepper Motor Driver Project

2009-06-20T05:18:00.000-07:00

Microstepping Stepper Motor Data

Microstepping of Stepping Motors
Introduction
Microstepping serves two purposes. First, it allows a stepping motor to stop and hold a position between the full or half-step positions, second, it largely eliminates the jerky character of low speed stepping motor operation and the noise at intermediate speeds, and third, it reduces problems with resonance.
Although some microstepping controllers offer hundreds of intermediate positions between steps, it is worth noting that microstepping does not generally offer great precision, both because of linearity problems and because of the effects of static friction.
1 Sine-Cosine Microstepping
2 Limits of Microstepping
- Detent Effects
- Quantization
3 Typical Control Circuits
- Practical Examples

http://www.cs.uiowa.edu/~jones/step/micro.html

Microstepping Stepper Motor Driver Kit

Basic design
It is a unipolar (or 5-wire type) driver. The motor must have
5 or 6 wires (or 8), as 4-wire motors are only for bipolar
and 4-WIRE MOTORS WILL NOT WORK WITH THIS BOARD.

The constant current system is crude but simple, it relies on
setting the base of the main transistors at a "set" level, then
this causes a "set" voltage across the sense resistor Rs, ie
maintains constant current. It does get some temp drift with
large currents, but it's simple and accurate enough with the
resistor values i've tested. It actually works quite well!

The brain has control of which of the 4 transistors are ON,
and sets 3 possible current levels, enough to do 6th stepping
and give 1200 steps/rev with hardware alone. The software I
have provided also will do pwm and give 18th stepping, which
is 3600 steps/rev, almost stepless operation.

The PIC has plenty of left over rom if you need to do motion
control or use the board as the complete brains and driver for
an entire machine. Up to 9 PIC in/out pins can be allocated to
the board.

http://www.piclist.com/tecHREF/io/stepper/linistep/lini_wks.htm

Micro-step driver

This circuit allows to connect a bipolar step motor to a personal computer through the parallel port. The circuit is, for safety reasons, optically isolated from the PC and it allows to manage motors up to 3A for phase. Moreover the digital interface allows to connect up to six motors to a single PC parallel port.
The more interesting aspect of this circuit is its ability to implement the microstep technique and to multiply up to 64 times the motor real steps number. As an example, a 200 steps motor could behave like "a virtual" 12.800 steps motor. This function is particularly useful when the spin speed is very low, in the order of fractions of rpm.

http://www.vincenzov.net/eng/design/microstep.htm

L6208 FULLY INTEGRATED TWO PHASE STEPPER MOTOR DRIVER

Modern motion control applications need more flexibility that can be addressed only with specialized IC products. The L6208 is a fully integrated stepper motor driver IC specifically developed to drive a wide range
of two phase (bipolar) stepper motors. This IC is a one-chip cost effective solution that includes several unique circuit design features. These features, including a decoding logic that can generate three different stepping sequences, allow the device to be used in many applications including microstepping. The principal aim of this development project was to produce an easy to use, fully protected power IC. In addition several key functions such as protection circuit and PWM current control drastically reduce external components count to meet requirements for many different applications.

Microstepping Stepper Motor Driver Circuit

http://www.st.com/stonline/books/pdf/docs/8607.pdf

MICROSTEPPING STEPPER MOTOR DRIVE
USING PEAK DETECTING CURRENT CONTROL

Stepper motors are very well suited for positioning applications since they can achieve very good positional accuracy without complicated feedback loops associated with servo systems. However their resolution, when driven in the conventional full or half step modes of operation, is limited by the configuration of the motor. Many designers today are seeking alternatives to increase the resolution of the stepper motor drives. This application note will
discuss implementation of microstepping drives using peak detecting current control where the sense resistor is connected between the bottom of the bridge and ground. Examples show the implementation of microstepping drives with several currently available chips and chip sets.

INTRODUCTION
Microstepping a stepper motor may be used to achieve one or both of two objectives; 1) increase the position resolution or 2) achieve smoother operation of the motor. In either case the basic theory of operation is the same. The simplified model of a stepper motor is a permanent magnet rotor and two coils on the stator separated by 90 degrees, as shown in Figure 1. In classical full step operation an equal current is delivered to each of the coils and the rotor will align itself with the resulting magnetic vector along one of the 45 degree axis. To step the motor, the current in one of the two coils is reversed and the rotor will rotate 90 degrees. The complete full step sequence is shown in figure 2. Half step drive, where the current in the coil is turned off for one step period before being turned on in the opposite direction, has been used to double the step resolution of a motor. In either full and half step drive,
the motor can be positioned only at one of the 4 (8 for half step) defined positions.[4][5] Therefore,
the number of steps per electrical revolution and the number of poles on the motor determine the resolution of the motor. Typical motors are designed for 1.8 degree steps (200 steps per revolution) or 7.5 degree steps (48 steps per revolution). The resolution may be doubled to 0.9 or 3.75 degrees by driving the motor in half step. Further increasing the resolution requires positioning the rotor at positions between the full step and half step positions.

Example alignment of microsteping

http://www.st.com/stonline/books/pdf/docs/8700.pdf

Precision Microstepping Driver Circuit

Microstepping Stepper Motor Driver Project

Functional description
The circuit can be divided into three functional blocks, Microprocessor simulation logic, micro-stepping controller and stepper motor driver.
A. Micro-stepping simulation.
This block send the control signals normally sent by a microprocessor to the micro-stepping controller, the inputs to the block are the 5 Dip-switches and the clock pulse from pin1 of J2. During normal operation the current level in one of the motor windings is updates at every step pulse (single pulse programming). These mean two step pulses are required to update both winding currents and make the motor turn. Operating the dip-switched S1-6 can change the direction of the motor rotation

http://home.att.net/~wzmicro/3960drv.html

Stepper Motor Driver Project

2009-06-10T23:26:00.000-07:00

Unipolar Stepper Motor Driver Circuit
This project presents a circuit for driving high-power unipolar stepper motors. Here you will find all the information needed to make your own. This circuit allows step-level control and can be easily modified for other modes of operation

Circuit Schematic and Photo
The L297 has several inputs that can be generated by a PC/104 stack or other controller. This circuit allows you to control each step, in full-step mode. Meaning: You can tell it to move one step in either direction (of course you can make it move fast and it will continuously rotate). The two inputs are a direction and a pulse. In the next section you will find a program to control this using xPC.

http://hades.mech.northwestern.edu/wiki/index.php/Unipolar_Stepper_Motor_Driver_Circuit

Stepper motor driver circuit
Stepper Motor Data
Stepper Motor Data 1
Stepper Motor Data 2
Stepper Motor Data 3
Microstepping Data
Stepper Motor Driver Circuit
2A Step Motor Driver Circuit
bipolar stepper motor with current control
Microstep Stepper motor driver circuit
Precision Microstepping Driver Circuit
High Current Microstep Stepper Motor Driver
http://basicelectronic.blogspot.com/2009/02/stepper-motor-driver-circuit.html

Stepper motor control board
This project is actually an educational kit. One can study the full operation of unipolar type stepper motor using this board. As it is micro controller based it can be programmable also and one can learn micro controller interfacing with LEDs, key board and stepper motor. Thus single board serves the purpose of learning stepper motor control as well as learning micro controller programming.

In the construction of unipolar stepper motor there are four coils. One end of each coil is tide together and it gives common terminal which is always connected with positive terminal of supply. The other ends of each coil are given for interface. Specific color code may also be given. Like in my motor orange is first coil (L1), brown is second (L2), yellow is third (L3), black is fourth (L4) and red for common terminal.

http://electrofriends.com/microcontrollers/stepper-motor-control-board/

Stepper motor controller
The stepper motor driver circuit shown as following

The opto-isolator are important which prevent destroy of MCU by the feeback voltage from
power transistor. Two adjust-able voltage regulator used to adjust the running voltage and
stopping/holding voltage of the stepper motor.

http://www.geocities.com/mindtan2000/PIC.html

Remote Unipolar Stepper Motor Controller with 89C51
Abstract:- This is the third and most amazing application of multichannel IR remote where 4 different channels of remote are utilized to control all the parameters of unipolar stepper motor. All three parameters of stepper motor RPM, direction & no. of revolutions can be changed from remote. 89C51 takes care of all the controlling actions.

The project is based on stepper motor control and I have experimented with unipolar stepper motor. One must know first how this stepper motor is controlled. How it can be rotated, how RPM, direction & no. of revolutions can be changed etc. So let us first go through the theory of unipolar stepper motor

http://www.jasonbabcock.com/computing/breadboard/bipolar/index.html

Controlling Stepper Motor with a Parallel Port
This is an easy to build stepper motor driver that will allow you to precisely control a unipolar stepper motor through your computer's parallel port. With a stepper motor you can build a lot of interesting gadgets such as robots, elevator, PCB drilling mill, camera panning system, automatic fish feeder, etc. If you have never worked with stepper motors before you will surely have a lot of fun with this project.

http://www.jasonbabcock.com/computing/breadboard/bipolar/index.html

Controlling Stepper Motor with a Parallel Port
This is an easy to build stepper motor driver that will allow you to precisely control a unipolar stepper motor through your computer's parallel port. With a stepper motor you can build a lot of interesting gadgets such as robots, elevator, PCB drilling mill, camera panning system, automatic fish feeder, etc. If you have never worked with stepper motors before you will surely have a lot of fun with this project.

http://electronics-diy.com/stepper_motors.php

Stepper Motor Controller
he stepper motors were purchased at a local auction house. They took apart old hard drives and printers and such selling the parts separately. You can usually barter and get a good deal, the ones being used in this circuit cost about $3 each. These particular motors are unipolar steppers. You can usually tell by the number of wires coming out. This one has 6 wires coming out of it: 2 green, 1 blue, 1 yellow, 1 red, and 1 white. In a 4 phase unipolar motor There are 2 coils which are center tapped and have a wire for each of phases. If the wire colours are random or if there were only 5 wires, then you would have to use an ohmmeter to distinguish between the phases and center tap. Fortunately for me 2 of the wires were the same colour, so they must be the center taps. Another plus was the wires were grouped in threes.

http://homepage.usask.ca/~avl094/Electronics/Stepper/

Stepper power board based upon L6208 circuit
Find herebelow my own design for stepper command board based upon L6208 circuit.

Stepper bipolar command (4 wires)
Maximum current 2.5A per phase
Mode : 1/2 step
Bridge control : 'Slow decay' (see datasheets)
Command Step/direction
Power supply unstabilised, but rectified and filtered, maximum 32V
Power supply stabilised, maximum 40V.
Forced blow on circuit required.

Board presented here is slightly different from prototype, i've locked it in half-step and control mode in 'Slow decay'. I've improve design and distance between wires.
This board don't have been tested at maximum current (only tested at 2A), nor in intensive service.

While integrated circuit accept a maximum current of 2.8A, i've limited the board to 2.5A.
I've tested without cooling, heating is intense (~100°C), and circuit disjunct over 1.8A. With a small blower, temperature remains very reasonnable

http://www.otocoup.com/CarteL6208_e.htm#Specif

LED Sequencer Circuit

2009-04-19T00:46:00.000-07:00

Descrete Multistage Light Sequencer Circuit
The drawing below illustrates a multistage light sequencer using
descrete parts and no integrated circuits. The idea is not new
and I hear a similar circuit was developed about 40 years ago
using germanium transistors. The idea is to connect the lights so
that as one turns off it causes the next to turn on, and so forth.
This is accomplished with a large capacitor between each stage
that charges when a stage turns off and supplies base current to
the next transistor, thus turning it on. Any number of stages can
be used and the drawing below illustrates 3 small Christmas lights
running at about 5 volts and 200mA. The circuit may need to be
manually started when power is applied. To start it, connect a
momentary short across any one of the capacitors and then
remove the short. You could use a manual push button to do this.

16 Stage LED Sequencer Circuit
The circuit below uses a hex Schmitt Trigger inverter (74HC14)

and two 8 bit Serial-In/Parallel-Out shift registers (74HCT164 or

74HC164) to sequence 16 LEDs. The circuit can be expanded to

greater lengths by cascading additional shift registers and

connecting the 8th output (pin 13) to the data input (pin 1) of the

succeeding stage. A Schmitt trigger oscillator (74HC14 pin 1 and 2)

produces the clock signal for the shift registers, the rate being

approximately 1/RC. Two additional Schmitt Trigger stages are

used to reset and load the registers when power is turned on.

60 Light Sequencer Circuit using a Matrix

The circuit below illustrates using a 10x10 matrix to sequence up

to 100 LEDs with just three ICs and 20 transistors. The two 4017

decade counters control the 10 rows and 10 columns so that one

LED is selected depending on the output of the decade counters.

The LED circuit is drawn showing 25 LEDs and 10 transistors but

can be expanded up to a 100 by using sucessive stages of the

4017 counters.

LED sequencer
The model 4017 integrated circuit is a CMOS counter with ten

output terminals. One of these ten terminals will be in a "high"

state at any given time, with all others being "low," giving a

"one-of-ten" output sequence. If low-to-high voltage pulses are

applied to the "clock" (Clk) terminal of the 4017, it will increment

its count, forcing the next output into a "high" state. With a 555

timer connected as an astable multivibrator (oscillator) of low

frequency, the 4017 will cycle through its ten-count sequence,

lighting up each LED, one at a time, and "recycling" back to the

first LED. The result is a visually pleasing sequence of flashing

lights. Feel free to experiment with resistor and capacitor values

on the 555 timer to create different flash rates

led flashing circuit

2009-04-18T00:38:00.001-07:00

Transistor LED flasher Circuit

This circuit has a lot going for it. For one thing, it only consists of two
transistors, two capacitors and four resistors. That also means it
consumes very little power. You can control the flash rate by changing
the size of the 100k resistors (100k makes for a pretty slow rate).
You can also control the duty cycle by using resistors of different
values on the two sides. The 470 ohm resistors control the current
through the LEDs. Normally you want to limit this to 20mA, but to
conserve battery power, you may need to limit it even further. You
can also connect several LEDs in series, instead of using only one
for each side. With red LEDs (1 per side) and the values shown,
the circuit draws about 11mA.
more

Basic LED flasher circuit using NE555 timer IC
This circuit consumes more power, but it's advantage is when

you need a variable flash rate, like for strobe circuits. You can

actually use this circuit as a remote control for strobes that have

a remote input. Of course, it has many other applications

besides strobes.

4 Parallel LEDs flashing circuit
Nominal flash rate: 1.3 Hz. Average IDRAIN e 2 mA

LM3909 LED Flasher/Oscillator
General Description
The LM3909 is a monolithic oscillator specifically designed
to flash Light Emitting Diodes. By using the timing capacitor
for voltage boost, it delivers pulses of 2 or more volts to the
LED while operating on a supply of 1.5V or less. The circuit
is inherently self-starting, and requires addition of only a battery
and capacitor to function as an LED flasher.
Packaged in an 8-lead plastic mini-DIP, the LM3909 will operate
over the extended consumer temperature range of
b25§C to a70§C. It has been optimized for low power drain
and operation from weak batteries so that continuous operation
life exceeds that expected from battery rating.
Application is made simple by inclusion of internal timing
resistors and an internal LED current limit resistor. As
shown in the first two application circuits, the timing resistors
supplied are optimized for nominal flashing rates and
minimum power drain at 1.5V and 3V.

more pdf

12 LED Flasher
LED flasher in this circuit use 12 LED it can show 2 style .

The circuit consist 2 section

1.5 volt dual LED flasher Circuit
This 1.5 volt led fasher runs more than a year on a single 'd" cell

and alternately flashes 2 LEDs at about a 1 second rate. The

circuit employs a 74HC14 CMOS hex inverter that will operate

at very low voltages (less than 1 volt). One section is used as a

squarewave oscillator (pins 1 and 2), while the others are wired

to produce a short 10mS pulse on alternate edges of the square

wave so the LEDs will alternate back and forth.

Infrared motion detector with Microcontroller Circuit

2009-04-16T22:57:00.000-07:00

A simple automatic motion-detection Digital Camera Circuit

When the sensor detects movement in a room it will take a burst of
10 photos with the digital camera. Each photo is taken at 0.5sec
interval. After the 10 photos, the camera waits 3 seconds for further
movement and if it is detected, the process is repeated until 80
photos are taken.
The photos can then be downloaded to your PC (via the USB
connection on the board) for viewing.

more

The Directional Infrared Detector Module Circuit (DIRM)

Figure shows a block diagram of the DIRM. A Fresnel lens
captures the incident IR and focuses it towards the
pyroelectric sensor increasing the sensitivity of the sensor
and improving its directional response. The resultant signal
passes through a low pass filter, which removes any high
frequency noise generated by mechanical vibration. The
output of the filter is then fed into a differentiator, which
produces an output voltage proportional to the rate of
change of the incident IR. The frequency response of this
differentiator is also rolled off at high frequencies, further
reducing the effects of undesired signals. The window
comparator produces a logic output whenever the rate of
change of incident IR exceeds a given set point.
An 8-bit PIC16F84 microcontroller processes the logic
signals and controls the rotating platform and reports
information to the team leader.

PIR DETECTOR USING ST7FLITE05 MICROCONTROLLER
A PIR detector can be made easily with ST7FLITE05 using the
circuit shown in Figure. The sensor interfacing circuit (shown on
the left side of the microcontroller in Figure ) can be divided
into the following modules:
1.Transistor circuit used as an amplifier.
2.Transistor biasing controlled through the microcontroller.
3. Software-controlled transistor output.

more pdf

Infrared, Alarm, and PIC Microcontroller
OBJECTIVES:
• Get familiar with an infrared emitter diode and receiver.
• Create an obstacle detector with an infrared emitter and receiver.
• Learn about PIC microcontroller and programming a PIC microcontroller.
• Write a PIC program and build the circuit of a household alarm system.

more pdf

Ultra-low Power Motion Detection using the MSP430F2013

A system capable of detecting motion using a dual element PIR
sensor is shown in Figure 1 using the MSP430F2013
microcontroller. Using the integrated 16-bit Sigma-Delta
analog-todigital converter and built-in front-end PGA (SD16_A),
the MSP430F2013 provides all the required elements for interfacing
to the PIR sensor in a small footprint. With integrated analog
and a 16MHz, 16-bit RISC CPU, the MSP430F2013 offer a great
deal of processing performance in a small package and at a low cost.

more pdf

PIR Infrared motion detector Circuit

2009-04-15T22:51:00.001-07:00

Infrared motion detector Circuit
The pyroelectric sensor is made of a crystalline material that
generates a surface electric charge when exposed to heat in the
form of infrared radiation. When the amount of radiation striking
the crystal changes, the amount of charge also changes and
can then be measured with a sensitive FET device built into the
sensor. The sensor elements are sensitive to radiation over a wide
range so a filter window is added to the TO5 package to limit
detectable radiation to the 8 to 14mm range which is most sensitive
to human body radiation.
Typically, the FET source terminal pin 2 connects through a
pulldown resistor of about 100 K to ground and feeds into a two
stage amplifier having signal conditioning circuits. The amplifier
is typically bandwidth limited to below 10Hz to reject high
frequency noise and is followed by a window comparator that
responds to both the positive and negative transitions of the
sensor output signal. A well filtered power source of from 3 to
15 volts should be connected to the FET drain terminal pin 1

more

MX063 PIR SENSOR LIGHT Circuit

Application Schematic of Pyroelectric Infrared Motion
Sensors Circuit
Note: For best results the power supply should be very stable
at a constant +5V DC +/- .2V.This Schematic is offered for reference only without warranty
of any kind. Microsystem Technologies does not support user
designs or implementations that use this circuit

Automatic security lights Circuit
Combination PIR sensor and floodlight units are cheap but
rather inflexible if you want to locate the sensor and light in
different places. In my case, I wanted to detect movement
on the driveway and switch on the lights in the carport around
the corner. Yet another job for the ubiquitous PICAXE-08
microcontroller

A standard PIR sensor is used as the movement detector.
The sensor interfaces to the PICAXE (IC1) on input 2 (pin 5).
This pin is pulled low via isolation diode D3 and the normally
open (NO) output of the sensor whenever movement is
detected. It can also be pulled low by transistor Q1, which acts
as a simple inverter for sensors with normally closed (NC) outputs.
more

Passive Infrared Motion Detector Circuit

This circuit was originally reverse -engineered from a motion
detecting yard light that I ripped apart. That's still probably the
best way to get the parts at a reasonable price, especially the
pyroelectric sensor and the absolutely necessary Fresnel lens.
The signal at pin 7 of the 324 is very interesting and fooling with
the filtering around the first amplification stage can make it even
more so. The LM324 is a wonderful little bug, and you will find
many uses for the window comparator if you look at it the same
way you would learn a new really useful knot. It all works on a
single 5 volt supply. The sensor is only sensitive to changes
across its surface, so don't expect a signal from a static object
even if it is hot. Yard lights are turning up at flea markets and yard
sales as people find themselves heads up every time the cat walks
past. This circuit is in a machine that sees people moving 40 feet
away.

4-20mA Current Loop Receiver Circuit

2009-04-09T03:27:00.000-07:00

4-20mA Current Loop Receiver with Input Overload
Protection circuit

The RCV420 is a precision current-loop receiver designed
to convert a 4–20mA input signal into a 0–5V
output signal. As a monolithic circuit, it offers high
reliability at low cost. The circuit consists of a premium
grade operational amplifier, an on-chip precision
resistor network, and a precision 10V reference. The
RCV420 features 0.1% overall conversion accuracy,
86dB CMR, and ±40V common-mode input range.

FEATURES
-COMPLETE 4-20mA TO 0-5V CONVERSION
- INTERNAL SENSE RESISTORS
-PRECISION 10V REFERENCE
- BUILT-IN LEVEL-SHIFTING
- ±40V COMMON-MODE INPUT RANGE
- 0.1% OVERALL CONVERSION ACCURACY
- HIGH NOISE IMMUNITY: 86dB CMR

A current-sensing circuit derives its power from the

4-20-mA current loop.

4-20mA Current Loop Receiver with fault protection and
digital-signal recovery circuit

Figure shows one form of flexible fault protection for the 24VDC
power supply of a 4-20mA loop. Also included is circuitry for recovering
a digital signal superimposed on that loop. U1 (a high-side current-
sense amplifier with comparator and reference) senses the loop current
in R1 as an 8-40mV voltage and amplifies it by 100, producing an
output-voltage range of 0.8V to 4V. That output (VOUT) can directly
drive external meters, strip-chart recorders, and A/D converter inputs.

More pdf

4-20mA Pressure Transducer Circuit

2009-04-08T03:24:00.000-07:00

Complete 4-20mA Pressure Transducer Solution with

PGA309 and XTR117

The XTR117 is a precision current output converter designed
to transmit analog 4-20mA signals over an industry-standard
current loop. It provides accurate current scaling and output
current limit functions.

XTR117 datasheet pdf

The PGA309 is a programmable analog signal conditioner
designed for bridge sensors. The analog signal path amplifies
the sensor signal and provides digital calibration for
zero, span, zero drift, span drift, and sensor linearization
errors with applied stress (pressure, strain, etc.). The calibration
is done via a One-Wire digital serial interface or
through a Two-Wire industry-standard connection. The
calibration parameters are stored in external nonvolatile
memory (typically SOT23-5) to eliminate manual trimming
and achieve long-term stability.

PGA309 datasheet pdf

4-20mA Current-Loop Transmitter Circuit

2009-04-07T03:20:00.000-07:00

The XTR117 is a precision current output converter designed
to transmit analog 4-20mA signals over an industry-standard
current loop. It provides accurate current scaling and output
current limit functions.

The on-chip voltage regulator (5V) can be used to power
external circuitry. A current return pin (IRET) senses any
current used in external circuitry to assure an accurate
control of the output current.

FEATURES
_ LOW QUIESCENT CURRENT: 130 uA
_ 5V REGULATOR FOR EXTERNAL CIRCUITS
_ LOW SPAN ERROR: 0.05%
_ LOW NONLINEARITY ERROR: 0.003%
_ WIDE-LOOP SUPPLY RANGE: 7.5V to 40V
_ MSOP-8 AND DFN-8 PACKAGES

XTR117 datasheet pdf

0-5V To 4-20mA Current-Loop Transmitter Circuit

The AM422 is a low cost monolithic voltage–
to–current converter specially designed for
analog signal transmission. The AM422 is
available in a 3– or 2–wire version, which allows
applications with flexible input voltage
ranges to be used for a standard output current.
Output current range and current offset level
are freely adjustable by external resistors. The
IC consists of three basic sections: an operational
amplifier input stage for single ended
input signals (0.5–4.5V, 0–10V, or other), a
programmable 4.5 to 10V reference for transducer
excitation, and a current output, freely
adjustable in a wide current range (4–20mA,
0–20mA, other). With the broad spectrum of
possible input signals the AM422 is a flexible
and multipurpose voltage–to–current converter
for single ended transducers or voltage transmission.

FEATURES
- Wide Supply Voltage Range: 6...35V
- Wide Operating Temperature Range: –40°C...+85°C
- Adjustable Voltage Reference:4.5 to 10V
- Operational Amplifier Input:0.5...4.5V, 0...5V, other
- Adjustable Offset Current
- Available as Three– (0/4...20mA) or Two–Wire Version (4...20mA)
- Adjustable Output Current Range
- Protection Against Reverse Polarity
- Protected Current Output

AM422 datasheet pdf

Constant Current Battery Charger Circuit

2009-04-06T03:16:00.001-07:00

Constant Current Battery Charger

Simple Power Supply and Charger Circuits
Figure 4 shows a simple power supply circuit. I have tested with KABO,
it works fine. For those who have a big capacity rechargeable battery,
the resistance value of R can be selected for approx. 10% output
charging current. DC in can be higher if your battery voltage higher than
8.4V, say. To ensure the output current is within the value calculated by
R, measure DC current before. The maximum supply for LM317 is ~35V.

A Simple Peak-detecting Nicad Charger
The circuit consists of two parts, a constant current generator using

a PNP power transistor (Q2), and a peak-detecting shutoff circuit

using a high-gain opamp (IC1). To start the charge cycle, switch

SW1 is momentarily closed, causing C1 to discharge. As IC1's

inverting input is now higher than its non-inverting input, its output

goes low, turning on Q1. This lights the red "charge" LED (D2) and

provides about 80mA through R6 and R7 to turn on Q2, which starts

charging the battery. Charge current flows through R8 on its way to

the battery. When the voltage across R8 exceeds about 0.6V, Q3

starts to turn on and robs current from the base of Q2. This regulates

the output current to an amount determined by the value of R8.

ADJUSTABLE CURRENT SOURCE Circuit

2009-04-04T23:44:00.000-07:00

The HIP5600 can supply a 450 A (20%) constant current.
It makes use of the internal bias network.

See Figure 27 for bias current versus input voltage.
With the addition of a potentiometer and a 10 F capacitor the
HIP5600 will provide a constant current source. IOUT is given
by Equation 13 in Figure 16.

FIGURE 16. ADJUSTABLE CURRENT SOURCE

1.5A ADJUSTABLE CURRENT SOURCE Circuit

The LM317 is an adjustable 3−terminal positive voltage regulator
capable of supplying in excess of 1.5 A over an output voltage
range of 1.2 V to 37 V. This voltage regulator is exceptionally
easy to use and requires only two external resistors to set the
output voltage. Further, it employs internal current limiting,
thermal shutdown and safe area compensation, making it
essentially blow−out proof.

The LM317 serves a wide variety of applications including
local, on card regulation. This device can also be used to
make a programmable output regulator, or by connecting a fixed
resistor between the adjustment and output, the LM317 can be
used as a precision current regulator.
Features
-Output Current in Excess of 1.5 A
-Output Adjustable between 1.2 V and 37 V
-Internal Thermal Overload Protection
-Internal Short Circuit Current Limiting Constant with Temperature
-Output Transistor Safe−Area Compensation
-Floating Operation for High Voltage Applications
-Available in Surface Mount D2PAK−3, and Standard 3−Lead
Transistor Package
-Eliminates Stocking many Fixed Voltages
-Pb−Free Packages are Available

Constant-Current Circuit

2009-04-03T21:07:00.000-07:00

Booster Constant-Current Circuit
Constant-current circuits can be configured to take
advantage of the fact that CMOS regulators consume
a very low current.

If you wish to set constant current value io to a
larger value, PNP transistor Tr1 and resistor R1 can be
added, as seen in Figure 5. This will improve the
input/output voltage characteristics, allowing you to
increase the said current value as a result.
Consequently, under the same conditions as stated
above, that is, an input voltage VIN of 3 V and a
device voltage VO higher than 1V, for example, the
drive capacity will rise from 10 mA (typ.) to 100 mA
(typ.).

Figure 4. Booster Constant-Current Circuit

Constant Current Battery Charger Circuit

The resistors R1 and R2 determine the final charging voltage
and RSC the initial charging current. D1 prevents discharge
of the battery throught the regulator.
The resistor RL limits the reverse currents through ther
regulator (which should be 100 mA max) when the battery
is accidentally reverse connected. If RL is in series
with a bulb of 12 V/50 mA rating this will indicate incorrect
connection.

Transistor constant current Circuit
This is a schematic of the smoke circuit regulator. This is a
constant current regulator. The two 1.5 ohm resistors sense
the current in the smoke elements. If the smoke element
current increases, the base voltage of the 2N3904 increases
and it in turn drags down the base of the TIP122 pass transistor
which reduces the voltage and therefore the current of the
smoke elements. The circuit regulates the current to about 1 amp.
The resulting voltage across the elements is about 6 volts. The
most significant internal voltages are shown in red referenced to
the (-) side of the bridge.

Constant Current for Sensor Excitation Circuit
Abstract:
The MAX1464 can be easily configured to generate constant

current excitation for sensors that is ratiometric to the power supply

voltage for resistive transducer applications. Applications utilizing

sensing elements with high temperature coefficients, TCR, such as

piezo resistive bridges, RTDs, etc. are typically implemented with

constant current excitation. This application note suggests a simple

resistive network that can be implemented to provide a ratiometric

current source for sensor excitation.

Transistor constant current source Circuit
The current source shared by the two transistors is also shown in the

figure. Due to the fact that the forward biased diodes have fixed

voltageVd = 0.7V, the base voltage of the transistor is also fixed at 2.1V

, so is the current Icc, i.e., the circuit can be used as a constant current source

Ramp Generator Circuit

2009-04-02T01:09:00.000-07:00

Dual Ramp Generator
The first circuit is a dual ramp generator where the positive
and negative ramps are generated separately. This circuit
was used as a ramp generator for a transistor curve tracer:
the positive going ramp was used for testing NPN transistors
and the negative ramp for testing PNP transistors.

Generating Triangle Waves
In the circuit to the right, we use a separate integrator to
generate a ramp voltage from the generated square wave.
As a result, we can get both waveforms from a single circuit.
The phase relationship shown between the two output
waveforms is correct

555 ramp generator
Again, we are using a 555 timer IC as an astable multivibrator,
or oscillator. This time, however, we will compare its operation
in two different capacitor-charging modes: traditional RC and
constant-current.

Ramp Generator by Schmitt trigger

Precision ramp generator produces a 0 to 5V ramp

The ramp is generated by a constant charging current into

capacitor CRAMP, which is connected between ground and

the noninverting input of op amp IC1, configured as a

voltage follower. The current through RRAMP is the charging

current, kept constant by forcing the voltage across RRAMP

to equal the reference voltage from IC1. One side of RRAMP

is connected to CRAMP, and the other side to the reference

output. In turn, the ground terminal of the reference IC connects

to the op-amp output, which provides a low-impedance replica

of the voltage across CRAMP

Linear Voltage Ramp
To make the ramp of the charging cycle linear with time the

capacitor must be charged from a constant current. R1 is

replaced with another PNP Q3, which implements a constant

current source. Q3's base voltage is fed from a diode drop,

leaving just a single resistor R1 to vary the charging current,

and hence frequency of oscillation.