Guide to Electrical Circuits Design

RS-232 POWER TEMPERATURE SENSOR CIRCUIT DIAGRAM

2011-07-28T02:24:00.000-07:00

RS-232 POWER TEMPERATURE SENSOR CIRCUIT DIAGRAM
The temperature sensor converts this temperature into a square wave with a frequency proportional to the absolute temperature of its package, while drawing little supply current from the power source. The amplitude of the output signal is equal to the power supply of the chip, and must be sent over a cable to the host system. The use of a RS-232 interface, low-power dedicated chip enables the communication, while providing power to the sensor.

ROOM TEMPERATURE CONTROLLER USING LM35 SCHEMATIC DIAGRAM

2011-07-27T01:32:00.000-07:00

ROOM TEMPERATURE CONTROLLER USING LM35 SCHEMATIC DIAGRAM
When the temperature on IC LM35 is low, the output voltage also low. If the electric voltage of the transistor is below the transistor active area, the voltage will be blocked, LED will off, relay for the fan circuit in open condition, thus the fan is off.

When the temperature of LM35 is high, the output voltage is also high. If the transistor electric voltage in the transistor’s active area, the LED will on, relay on the fan in close condition, thus the fan will be turn on.

Components :
Resistor R1 : 10k ohm
Resistor R2 : 4.7M ohm
Resistor R3 : 1.2k ohm
Resistor R4-R5 : 1k ohm
Resistor R6 : 330 ohm
Capacitor C1 : 0.1 uF
Polar capacitor C2 : 470 uF/25V
IC1 : LM35
IC2 : TL431
IC3 : LM358
Q1 Transistor PNP : BC557
Zener diode D6 : 13V/400mW
Diode D1-D2 : 1N4148
Diode D3-D4 : 1N4007
Relay K1 : 12V SPDT
LED
12V power supply

PHONE CONVERSATION RECORDER SCHEMATIC DIAGRAM

2011-07-26T22:19:00.000-07:00

PHONE CONVERSATION RECORDER SCHEMATIC DIAGRAM
D1-D4 diodes serves as a device to convert the alternating current from the telephone line to become direct current in order to be used as a voltage activator. 12V zener diode lowers the voltage to 12V. When the phone receiver has not been appointed, the T1 voltage value will be low. This causes the transistor T2 on its cut off state and deactivate the relay. If the phone receiver is picked up, the voltage flows from T1 to T2. This activates the relay and turn the tape recorder on.

Components list :

Resistor R1 : 8k ohm
Resistor R2 : 2k2 ohm
Resistor R3 : 1M ohm
Resistor R4 : 100k ohm
Resistor R5 : 4k7 ohm
Diode D1-D4, D6 : 1N4001
Zener diode D5 : 12V
Transistor T1-T2 : BC548
Polar capacitor C1 : 0.001 uF/150 V
Polar capacitor C2 : 100 uF/25 V
Relay : 6V, 100 ohm

MAGNETIC SENSOR SCHEMATIC CIRCUIT DIAGRAM

2011-07-22T00:19:00.000-07:00

MAGNETIC SENSOR SCHEMATIC CIRCUIT DIAGRAM
The principle of this circuit is, whenever a magnet comes close to the sensor, then the sensor will flow the output voltage to IC1. The output voltage will activate the timer which will then activate the relay controlled by IC2.

Component List :

Diode D1 : 1N4001
Resistor R1 : 10k ohm
Resistor R2 : 470k ohm
Resistor R3 : 1k ohm
Resistor R4 : 47k ohm
Polar capacitor C1 : 2.2 uF/16V
Polar capacitor C2 : 470 uF/16V
Transistor T1 : SL100
IC1 : NE555
IC2 : CD4013
Relay RL1 : 12 V, 200 ohm
Magnetic Sensor
5mm LED

LOCAL TELEPHONE LINE WITH DIVERTING SWITCH CIRCUIT SCHEMATIC DIAGRAM

2011-07-22T00:14:00.000-07:00

LOCAL TELEPHONE LINE WITH DIVERTING SWITCH CIRCUIT SCHEMATIC DIAGRAM
In normal state, telephone no.1 and telephone no.2 can be used as an intercom when telephone no.3 is connected with the phone cable. To be used as an intercom, pick up telephone no.1 and push switch S1, then piezo buzzer 2 will sound, and so on.

Components :
Resistor R1 : 4.7k ohm
Polar capacitor C1 : 2.2uF/100V
PZ1-PZ3 : Piezo buzzer
S1-S2 : Push button
S3 : ON/OFF stereo switch
12V DC/200 mA power supply

HEADPHONE CIRCUIT FOR FIXED TELEPHONE LINE SCHEMATIC DIAGRAM

2011-07-21T05:03:00.000-07:00

HEADPHONE CIRCUIT FOR FIXED TELEPHONE LINE SCHEMATIC DIAGRAM
This circuit requires low power, therefore can be installed parallel with the telephone. Transistor T1, Resistor R2,R3, and Zener diode are used to lower the input voltage become 5V. Transistor T2, resistor R6,R7, and capacitor C5 are used as the sound amplifier. This circuit is equipped with condenser microphone to speak and earphone to hear.

DIGITAL VOLUME CONTROL SCHEMATIC DIAGRAM

2011-07-20T03:45:00.000-07:00

DIGITAL VOLUME CONTROL SCHEMATIC DIAGRAM
It uses one IC DS1669 and some additional components. S1 works as an addition to audio volume, S2 works as audio volume subtractor.

Components list :

Capacitor C1 : 0.1 uF
Switch S1-S2 : Push button
IC : DS1669
5V DC power supply

DIGITAL COMBINATION LOCK CIRCUIT DIAGRAM

2011-07-20T03:42:00.000-07:00

DIGITAL COMBINATION LOCK CIRCUIT DIAGRAM

The output of this circuit can be connected with relay as an ON/OFF control to the electronic devices. This circuit works with 5-12V power supply. To store the combination, connect the IC push button switch with the pin 3,4,5, and 6. For an example, S1 with pin 3, S2 to pin 4, S3 to pin 5, and S4 to pin 6. This will result 1234 combination. Connect S5-S8 with pin 2. This will cause to reset the IC if the combination is wrong. Relay will turn to active when the combination is correct.

Components :
Diode D1 : 1N4148
Volt regulator IC : LM317
Polar capacitor C1 : 1 uF/25V
Polar capacitor C2 : 220 uF/25V
Resistor R1 : 2.2k ohm/4 W
Resistor R2 : 1k2 ohm
Transistor Q1 : 2N3904
IC1 : LS7220
S1-S12 switch : push button
Header
SPDT relay : 12 V
12 V power supply

DAILY WAKE UP CALL ALARM CIRCUIT SCHEMATIC DIAGRAM

2011-07-20T03:39:00.000-07:00

DAILY WAKE UP CALL ALARM CIRCUIT SCHEMATIC DIAGRAM

When the sensor doesn’t receive any light (night time), the transistor basis would have 1 (high) value, so the emitor value is 0 (low). The low value in the emitor would reset the IC timer. The circuit’s value would change when the sensor exposed by morning light. This condition would turn on the IC555 and produce sound on the speaker. Sensor sensitivity can be adjusted by turning the variable resistor to find the proper value.

Components :
Resistor R1 : 10k ohm
Resistor R2 : 3K3 ohm
Resistor R3 : 56k ohm
Resistor variable VR1 : 100k ohm
Transistor TR1 : BC158
Polar capacitor C1 : 1uF/15V
Capacitor C2-C3 : 0.01 uF
IC timer : NE555
LDR light sensor
Speaker : 8 ohm/0.5W
ON/OFF switch
9V power supply

CHRISTMAS STAR LAMP SCHEMATIC DIAGRAM

2011-07-19T18:39:00.000-07:00

CHRISTMAS STAR LAMP SCHEMATIC DIAGRAM

The lamp will turn on from darkness into its maximum brightness and then goes back to dim. The lamp intensity is influenced by C3 capacitor. IC2 is an optoisolator, and IC1 acts as astable multivibrator. IC1 frequency can be changed by changing the values of R2 and C1.

Components list :

Diode D1-D5 : 1N4007
DIAC : DB3
Resistor R1 : 1k ohm
R2 : 100k ohm
R3-R4 : 10k ohm
R5 : 270k ohm
Resistor variable VR1 : 1M ohm
Polar capacitor C1 : 47uF/25 V
Capacitor C2 : 0.01 uF
Polar capacitor C3 : 470 uF/25 V
Polar capacitor C4 : 0.1 uF/400 V
Transistor SCR : TYN6004,4A,400 V
IC Timer IC1 : ne555
Optoisolator IC2 : MCT2E
Light bulb 220V AC
9V power supply

CHRISTMAS FLASHING LIGHT CIRCUIT

2011-07-17T19:09:00.000-07:00

CHRISTMAS FLASHING LIGHT CIRCUIT

Triggering control of the SCR done by Q1, Q2, and related resistors. Timing depends on R1, R2, and C1. If you want to change the frequency, set the C1 value from 100uF to 2200uF instead of modifying the values of R1 and R2, because they already set for the proper current and voltage point. Best performances can be achieved with C1=470 or 1000µF and R4=12K or 10K. A number of 10 to 20 lamp in series for Christmas trees (60mA @ 220V typical for a 20 lamp series-loop) is common, and this low current consumption only need a cheap SCR devices, e.g. C106D1 (400V 3.2A) or TICP106D (400V 2A), and the last, the most recommended is P0102D devices having TO92 case. [Circuit schematic diagram source: ELECTRONICS WORLD "Circuit Ideas", June 2000 issue, page 458].

AUTOMATIC TRAFFIC CONTROL LDR SCHEMATIC DIAGRAM

2011-07-17T19:07:00.000-07:00

AUTOMATIC TRAFFIC CONTROL LDR SCHEMATIC DIAGRAM

When the light is dark (high resistance value of LDR), electric current is small. Since the electric current is small and it value less than the transistor’s active voltage, the electric current will be blocked, AC lamp circuit closes, and the light turns on. When the light is bright (low resistance LDR value), electric current is high. Since the electric current is high and its value is larger than the transistor’s active voltage, the electric current passes, relay turn ON position, AC lamp open, and the light turns off.

Components list :
R1 : LDR
Resistor Variable R : 10k ohm
R3, R4 : 1k ohm
Q1, Q2 resistor : 2N2222
Relay K1 : 9V relay type SPDT
L1 : Bulb lamp 220V AC
Fuse F1 1 Ampere
9V power supply

AUTOMATIC ROOM LIGHT SCHEMATIC DIAGRAM

2011-07-17T19:05:00.000-07:00

AUTOMATIC ROOM LIGHT SCHEMATIC DIAGRAM

This circuit uses two LDR sensors put separately with 0.5m distance. Make sure to shut the LDR sensor tightly, in order not to be influenced by the light from outside. The output for this circuit is a 220V AC bulb lamp.

Components :
Diode D1-D4 : 1N4001
Diode D5-D8 : 1N4007
Diode D9-D10 : 1N4148
Resistor R1,R3 : 33k ohm
Resistor R2,R4-R8,R10-R13,R15 : 10k ohm
Resistor R9 : 100 ohm
Resistor R14 : 470 ohm
Resistor variable VR1 : 100k ohm
Capacitor C3-C4 : 0.01 uF
Polar capacitor C7,C9 : 1 uF/25 V
Capacitor C8,C10 : 0.1 uF
IC1-IC2 : NE555
IC3-IC4 : CD4017
IC5 : 74LS04
IC6 : 74LS08
Transistor T1-T4 : BC148
Transistor T5 : SL100
Sensor LDR1-LDR2 : LDR
Switch S1 : Push button
Switch S2 : SPDT switch
Relay R7 : 9V 200 ohm
9V power supply
Polar capacitor C1-C2, C5-C6, C11-C12 : 4.7 uF/25 V

AUTOMATIC LDR LIGHT SCHEMATIC DIAGRAM

2011-07-17T19:02:00.000-07:00

AUTOMATIC LDR LIGHT SCHEMATIC DIAGRAM
Since the non-inverting reference frequency is higher than the inverting input voltage, the IC ouput value is ’1'. Transistor in ‘ON’ state, relay is also ‘ON’, thus the AC light will be close and the light turns on.

When it’s bright or the resistor value of LDR is low, the current is high. Since the inverting input voltage is higher than the non inverting reference voltage, the IC output is ’0', transistor in ‘OFF’ state, thus the AC open and the light turns off.

Components List :

Resistor R1,R2,R3 : 10k ohm
Resistor R4 : 270k ohm
Resistor R5 : 4k7 ohm
Resistor R6 : 1k ohm
R8 : LDR
Resistor variable R7 : 1M ohm
IC UA741
Diode D1 : 1N4007
5mm LED
Transistor Q1 : BC109
Light bulb
9V relay
9V battery

AUDIO FREQUENCY LIGHT MODULATOR SCHEMATIC DIAGRAM

2011-07-16T01:52:00.000-07:00

AUDIO FREQUENCY LIGHT MODULATOR SCHEMATIC DIAGRAM
The distance between receiver and transmitter circuit depends on the environment. Light has function to replace cable from audio source to speaker. Transformer X2 is utilized to lock the audio signal. VR1 works as the amplitudo modulator from the T1 signal output.

Parts list :

Resistor R1: 47k ohm
Resistor R2 : 22k ohm
Resistor R3 : 220 ohm
Diode D1-D7 : 1N4001
VR1 : 1k ohm
Polar capacitor C1 : 470 uF/25V
Polar capacitor C2 : 1 uF
Capacitor C3 : 0.1 uF
Transistor T1-T2 : BC148
Transformer X1 : 220 V AC/0-12V AC
X2 : AF output
Transistor SCR1-SCR2 : BA654

METAL DETECTOR SCHEMATIC USING BEAT FREQUENCY OSCILLATOR CIRCUIT DIAGRAM

2011-07-15T01:56:00.000-07:00

METAL DETECTOR SCHEMATIC USING BEAT FREQUENCY OSCILLATOR CIRCUIT DIAGRAM

Schematic Diagram of The Metal Detector Circuit,
Metal detecting with beat frequency oscillator is one of the simplest method. The circuit basically have two balanced oscillators. The first provides the reference signal, and the other acts as the detector element. The frequency for the reference is fix, and the other one varies depending on the presence of a metal. This reference oscillator can be built using various circuit topology : LC (inductor-capacitor), RC (resistor-capacitor), or quartz oscillator. The detector oscillator uses LC because the mechanism will use the magnetic induction property of the detected object, and the inductor component will detect the probe.

The NAND gates use CMOS 4011 chip, a low power component that is suitable for this battery-operated circuit. You can see that this chip is supplied by a 5V voltage coming from an LM7805L regulator. You might wonder what the purpose of this regulation is, since the power supply come from a 9V battery and the CMOS gates can handle the voltage of 3-15 Volt. The main purpose of the regulator is to keep a constant voltage source for the reference oscillator frequency stability, since the frequency is affected by the power supply voltage variation as the battery voltage drops in the long time of usage.

This circuit uses parts as follows :

U1: CD4011
U2: LM389
U3: 78L05
R1: 2.2k 5%
P2: 4.7k lin.
R3: 330k 5%
R4: 270k 5%
R5: 1k 5%
C1: 390pF (NPO)
C2,C3,C4: 10nF
C5: 10uF 16v electrolytic
C6,C8: 220 uF 16v electrolytic
C7: 100uf 16v electrolytic
C9: 100nF ceramic
P1: 4.7k log
L1: 22cm in diameter with 14 turns AWG 26
K1: SPDT toggle switch
J1= Headphone jack 1/4 or 1/8 inch
Other parts: 9v battery connector, speaker or headphones

SCANTOOL OBD-II INTREPRETER MODULE

2011-07-15T01:54:00.000-07:00

ScanTool OBD-II Intrepreter Module in a DIP-24 Package
microOBD 200 (#440101) is a complete OBD?II interface in a vibration-resistant DIP-24 module. The only product of its kind, it offers engineers a simple and inexpensive way to add OBD-II support to any embedded project and tap into the wealth of information available on the vehicle’s communication bus. The interface is fully compatible with the popular ELM327 command set and supports all legislated OBD-II communication protocols, as well as the heavy-duty SAE J1939. It features automatic protocol detection, a large memory buffer, a UART interface capable of speeds of up to 10 Mbps, and a bootloader for easy firmware updates. The microOBD draws less than 1 mA in Standby mode, which makes it suitable for permanent in-vehicle installations. The host can force the module to enter the lowpower state by sending it an explicit “sleep” command or pulling the digital “host present” pin low. The module can also put itself in Standby automatically on UART inactivity or by sensing that the engine is off. Typical applications include diagnostic scan tools, code readers, data loggers, digital dashboards, fleet management, and vehicle tracking.

POWER INTEGRATION ICS AUTOMATIC AND SAFETY

2011-07-15T01:50:00.000-07:00

Power Integration ICs Automatically and Safely Discharge X Capacitors

CAPZero acts as a smart high-voltage switch when placed in series with discharge resistors. When AC voltage is applied, CAPZero blocks current flow in the X capacitor safety discharge resistors, reducing the power wasted in these components to zero at 230 VAC. When the AC voltage is disconnected, CAPZero automatically and safely discharges the X capacitor by closing the circuit through the bleed resistors and directing the energy away from the exposed AC plug. This approach provides engineers with total flexibility in their choice of the X capacitor used to optimize differential- mode EMI filtering without worrying about the effect of the required bleed resistors on system no-load and standby power budget. The innovative design inherently meets international safety standards for all open and short-circuit fault tests, allowing CAPZero to be used before or after the system input fuse. CAPZero is suitable for all AC-DC converters with X capacitors that require very low standby power. It’s offered with 825- or 1,000-V MOSFETs to support a variety of power supply design needs. It is ideal for a wide range of applications, including PCs, servers/workstations, monitors and TVs, printers and notebooks, and appliances requiring EuP Lot 6 compliance and adapters requiring ultra-low no-load consumption. CAPZero devices are available now in an SO-8 package at $0.40 each for 10,000- piece quantities. [www.powerint.com]

POWER CONVERTER TOPOLOGY AND MOSFET SELECTION FOR 48V TELECOM APPLICATIONS SCHEMATIC

2011-07-14T00:53:00.000-07:00

POWER CONVERTER TOPOLOGY AND MOSFET SELECTION FOR 48V TELECOM APPLICATIONS SCHEMATIC
A typical specification can range from a low of 36V to a high of 72- with a 48-V nominal. In some designs, transients in excess of 100V need to be considered. Most of these designs will require input to output isolation of up to 1500V.

Output voltages are frequently 5V and below with 3.3V probably the most common requirement, and 2.5V gaining in popularity. If a processor is on the card, voltages as low as 1.3V are not unlikely. One common approach is to regulate a distributed power bus, say the 5V rail, and then use non-isolated DC/DC converters to generate lower voltages. With the tendency away from 5V, the 3.3V rail is beginning to serve as the distributed bus, although, from the power supply designer’s perspective, this is not the most of desirable situations.

Fairchild has recently introduced a family of high voltage MOSFETs ranging from 80- to 200-V drain voltage specifications. This application note will provide information helpful in the proper selection of FETs for primary side switches – available in various types of 48V power converters.

PHONE BROADCASTER CIRCUIT SCHEMATIC DIAGRAM

2011-07-14T00:51:00.000-07:00

PHONE BROADCASTER CIRCUIT SCHEMATIC DIAGRAM

circuit diagram of phone broadcaster is useful to hear the conversation between persons who use the telephone. This circuit doesn’t need additional power supply, as it is only need the power from the telephone line. The circuit has two sections, the automatic switching, and the FM transmitter.

The automatic switching consists of resistors R1-R3, variable resistor VR1 as the regulator, transistor T1 and T2, zener diode D2, and diode D1. R1 and VR1 is useful as an input voltage divider from the telephone line.

Parts list :

Resistor R1-R2, R4 : 47k ohm
Resistor R3 : 100 ohm
Resistor R5 : 22k ohm
Resistor R6 : 1M ohm
VR1 : 100k ohm
Diode D1 : 1N4001
Zener diode D2 : 24V, 400mA
Capacitor C1 : o.o1 uF
Capacitor C2 : 330 pF
Trimmer C3 : 50p
Capacitor C4 : 5.6 pF
Capacitor C5 : 10 pF
Transistor T1-T2 : BC548
Transistor T3 : BF494
Inductor L1 : 45rotation 36SWG in resistor carbon 1M 1W
Inductor L2 : 3 rotation 21 SWG 12mm diameter
Antenna

MOUSE REPELLENT CIRCUIT SCHEMATIC DIAGRAM

2011-07-14T00:49:00.000-07:00

MOUSE REPELLENT CIRCUIT SCHEMATIC DIAGRAM

It uses IC timer NE555. When the circuit at its close state, the IC will control the buzzer time using the resistor and capacitor. The buzzer sounds like alarm in the different frequencies.

Resistor R1 : 1.8k ohm
Resistor R2 : 1k ohm
Resistor R3 : 5.6k ohm
Resistor R4 : 480 ohm
Capacitor C1 : 2.2 nF
Polar Capacitor C2 : 0.022uF/6V
IC1 timer : NE555
Speaker SP1 : Tweeter 8 ohm
Power supply : 5V

MOSQUITO REPELLENT CIRCUIT SCHEMATIC DIAGRAM

2011-07-14T00:45:00.000-07:00

MOSQUITO REPELLENT CIRCUIT SCHEMATIC DIAGRAM

mosquitos coming to you. It uses IC CD4047 to control the buzzer timing utilizing resistor and capacitor. When the voltage passing through the transistor, the buzzer would sound.

Variable resistor R1 : 10K ohm
Polar capacitor C2 : 4.7 nF/16V
Capacitor C3 : 22uF
IC1 : CD4047
NPN transistor Q1-Q2 BC547
PNP transistor Q3-Q4 BC557
Buzzer K1 : Tweeter 8 ohm
Power supply : 12V

CAR EXTERIOR LIGHTS CIRCUIT DIAGRAM

2011-07-13T02:38:00.000-07:00

Mitsubishi Montero Exterior Lights Circuit Schematic Diagram

Mitsubishi Montero 1994 is shown in the following figure. It shows the connection and wiring between each parts and component of exterior lights system of the vehicle such as the fusible link, junction block, tail light relay, cruise control, stop light switch, relay box, column switch, rear combination light, front combination light, license light, hazard light switch, turn-signal and hazard flasher unit, park/neutral position switch, back-up light switch, combination meter, and many more.

MINI AUDIO AMPLIFIER SCHEMATIC DIAGRAM

2011-07-13T02:36:00.000-07:00

MINI AUDIO AMPLIFIER SCHEMATIC DIAGRAM
“mini” audio amplifier referring to its small dimension and small output. It is intended for earpiece/earphone use. The characteristics are consume power less than 3mA, using push-pull output which can drive the earpiece to very loud level when audio is detected, whole circuit DC coupled, therefore makes it difficult to set up. Due to its size, be careful when assemble the circuit.

The 8k2 across the 47u sets the emitter voltage on the BC 547 and this turns it on. The collector is directly connected to the base of a BC 557, called the driver transistor. Both these transistors are now turned on and the output of the BC 557 causes current to flow through the 1k and 470R resistors so that the voltage developed across each resistor turns on the two output transistors. The end result is mid-rail voltage on the join of the two emitters. The two most critical components are 8k2 between the emitter of the first transistor and 0v rail and the 470R resistor.

LOW NOISE WHITE LED DRIVER SYSTEM SCHEMATIC DIAGRAM

2011-07-13T02:30:00.000-07:00

LOW NOISE WHITE LED DRIVER SYSTEM SCHEMATIC DIAGRAM

LM3570 is a parallel white LED driver capable of running directly off of a lithium-ion battery. The LM3570 has three parallel white-led drivers and a regulated VOUT pin (4.35V) capable of driving keypad or caller id display (CLI) diodes through the use of ballast resistors. The LM3570 evaluation board has a chip enable pin (active high logic) as well as a PWM (active high logic) pin which allows current sources to be turned on and off without completely disabling the part..The LM3570 is capable of supplying up to 80mA of current split between the regulated current sources and VOUT. The LM3570 comes in National’s LLP-14 package.