Electronic Parts, Kits and Projects

Simple Home Alarm System

2008-11-14T21:43:00.000-08:00

This Home Alarm System is simple, secure, fast and cheap. It's only few components with maximum security with Rolling Code TX and Shock Sensor with variable sensitivity. The alarm module can be assembled in only 2 hours and it don't need manual preset.

Home Alarm System with this characteristics is the most cheap system and the total cost could be reduced using a normal external sounder (escl. AG8).GSM module will be add in the future for a remote control.

The blue led connected to the pin RA3 of micro controller is used like a memory to know if the home alarm system has been activated by an event and its reset after a reactivation. The red led connected to the power supply before the 1N5406 diode is used to check the power supply connection. Of course the other 3 micro led red near the relays are used to check the output state.

Here you can download the last version of The Home Alarm System date 10 July 2007:

Home Alarm System in detail

Temperature Data Logger 4 Channel

2008-11-10T19:38:00.000-08:00

Here's a temperature data logger circuit, an 8-pin microcontroller based circuit for temperature data logging via the serial port of any computer from between 1 and 4 remote digital temperature sensors, DS1820/DS18S20 made by Dallas.

Features of the Temperature Data Logger are are follow:

Provides realtime data via the serial port.
Interfaces up to 4 x DS1820 sensors.
Accuracy to 0.5 degrees centigrade
Fahrenheit scale selected by a jumper
No external power required
Data stream easily logged & processed.
Over 200m distance for each sensor

The sensors of temperature data logger may be located more than 200 yards from the PCB. Just check that the remote VDD is above 4.4Volts. It's recommends 10uF tantalum capacitors be placed across the power supply pins (not supplied) to minimise random errors and possibly get increased range.

Download :
- Circuit Schematic and Parts List
- Sensor Specs DS1820 DS18S20
- Software for Windows and DOS
- Source Code
- Terminal Emulator

More about Four Channel Temperature Data Logger

Extech Digital Psychrometer Infrared Thermometer

2008-11-08T01:50:00.000-08:00

Temperature can be measured using a wide variety of sensor types. Some of the more common types found in manufacturing plants are thermocouples and RTDs (resistive temperature devices) contact and infrared non-contact measurement.

Infrared Non-Contact Measurement
All objects emit infrared energy, and the hotter an object is, the more active its molecules are, and the more infrared energy it emits. Infrared thermometers sense emitted, reflected, and transmitted energy from an object and translate this information into a temperature reading. Energy passes through the infrared thermometer’s optical system and is converted to an electrical signal, which is then converted and displayed as a temperature reading.

Infrared thermometers offer some distinct advantages over contact thermometers, since they can measure temperature without physically touching the object. Infrared temperature measurement is ideal for measuring objects that:

Are too far or to difficult to reach
Require non-contamination from one reading to the next
Are moving, rotating or vibrating
Are too time consuming for contact sensors and require quick temperature measurements
Have high temperatures up to 3,000 F
Can be scratched or damaged by physical contact
Have curved, distorted or varying surface conditions
Are too thin and soft for contact sensors
Are too hot to touch or approach
Are electrically active and too dangerous to touch ( by Pete Leal)

Description of Extech RH405 Digital Psychrometer IR Thermometer Kit:
Extech RH405 Digital Psychrometer IR Thermometer Kit includes: RH401 Digital Psychrometer, 33% to 75% calibration bottles, PC cable and carrying case.

See more RH401 Digital Psychrometer Infrared Thermometer Datasheet

See more EXTECH products

Variable DC Power Supply 1.5-15V

2008-11-08T01:08:00.000-08:00

This is variable DC power supply for all your projects. It has three fully regulated DC supply outputs and two AC center tap outputs. Two DC outputs are continuously variable and one is fixed. Both AC outputs are fixed.

For detailed circuit of the variable DC Power Supply see schematic below:

DC Power Supply Specifications:

Output DC: 1) 1.5VDC - 15VDC @ 1Amp, 2) -1.5VDC to -15VDC, 3) 5VDC @ 3 Amps.
Output AC: 1) 6.3VAC @ 1Amp, 2) 12.6VAC @ 1Amp
Input: 110VAC (line cord included).
Includes full enclosure and knobs.
Features short circuit protection on all supplies.
Variable DC outputs can be stacked to get 3-30VDC @ 1Amp.

See DC Power Supply Project documentation for complete details, including schematic and theory of operation.
More info about Practical Bench AC/DC Power Supply.

Used Test Equipment Fluke 5101A

2008-11-07T10:21:00.000-08:00

Here's an Used Test Equipment Fluke 5101A. The Fluke Model 5101A Calibrator has a wide range of DC voltages and current: AC voltages, current and dBm: and resistance output which is programmable from the front panel or through the optional remote interface.

The 5101A used test equipment has all the features of the Fluke Model 5100A plus an integral storage system of a memory and tape cassette which allows the operator enter or record a program to step the calibrator through a predetermined sequence.

Some common features of this test equipment series is DC voltages of 0 VDC to 1100 VDC and DC current of 10 µADC to 2 ADC: AC voltages of 1mVAC to 1100 VAC @ 400 Hz and a 20 VAC maximum 20 kHz to 50 kHz and AC current of 10 µAAC to 2 AAC: and resistance of 1 ohm to 10 Mohm and a four terminal measurement capability of 1 ohm to 10 kohm.

Download Fluke 5101A Test Equipment Datasheet
Fluke Model 5100A plus an integral storage system of a memory and tape
cassette which ....

More about Fluke 5101A Test Equipment
Calibrator, Data Acquisition, Frequency Counter, Function Generator,
Multimeter, ... and Spectrum Analyzer.

High Voltage Power Supply

2008-10-28T01:52:00.000-07:00

Here's an Universal high voltage power supply kit. This HV power source may be used in a variety of different high voltage applications, like:

Kirlian photography
HeNe Laser tube power supply
X-ray tubes
Plasma tubes
Negative ion generators, etc.

The power supply features variable frequency control using a potentiometer. Also has a High-Low frequency range switch. In addition this circuit to be either be battery powered 6-9 VDC, or powered from a wall transformer also 6-9 V with either an AC or DC output. When powered from batteries provides the advantage of portability for fieldwork.

Download :

Construction Manual
Construction Tutorial Video Lo-Res (WMV File 7.52 Mb)
Construction Tutorial Video Hi-Res (WMV File 16.9 Mb)

More Detail for High Voltage Power Supply Kit

Car Alarm with Remote Control

2008-10-28T01:07:00.000-07:00

This car alarm is full of potential, able to connect up with and operate a variety of sensors. In addition, the remote control facility (RF) allows the central locking system to be operated together with car alarm.

This car alarm is an advanced skill level electronic kit. Velleman rates this kit a skill level 5 on a scale from 1 to 5. Assembly is required. Interested in a much simpler and more basic car alarm option.

This car alarm have three section of diagram :

Remote Transmitter Diagram
Remote Receiver Diagram
Main Diagram

Below is Remote Transmitter diagram (please download manual for more)

Download Car Alarm With Remote Control Documentations:
car alarm - assembly manual car alarm - user manual

More about Car Alarm with Remote Control

15 Hz - 8 MHz Frequency Counter/Frequency Meter

2008-10-05T20:24:00.000-07:00

Here's a design for a simple, low-cost digital frequency counter meter. The frequency counter circuit is built around a member of the PIC family of microcontrollers from Arizona Microchip. In fact the most junior member of that family - the 16C54.

The features of the frequency counter :

operating frequency range from about 15Hz to 8MHz (sufficiently high to make the counter useful for troubleshooting digital circuits, microcontrollers etc.)
internal accuracy ± 1Hz
4 digits of displayed accuracy (enough accuracy for most situations)
adaptive (no range switch)
input conditioning amplifier sensitive to 50mV
input protection
crystal controlled (therefore no need for calibration)
powered by a single 9V alkaline battery

The frequency counter / meter circuit can be divided into three main parts - the power supply, the input amplifier, and the digital circuitry.

Power Supply
The meter is intended to be portable and can be powered by a 9V alkaline battery. A voltage regulator is used to stabilise the supply rail to 5V. It is important for accuracy that the microcontroller has a good power supply and the regulator does this very well.

Input Amplifier
The input amplifier is the interface between the input signal and the PIC microcontroller, and its function is to condition the signal before it passes to the RTCC pin. It will convert any periodic signal (sine, triangular, square wave etc.) with a peak to peak amplitude of at least 50mV into a clean 5V TTL-level square wave as required by the RTCC input. The amplifier has a high input impedance to minimise its effect on the input signal.

Digital Circuitry
A standard power-on reset circuit is provided for the PIC. Components C8 and R13 hold the voltage at MCLR near zero volts until the PIC's oscillator has stabilised. Resistor R14 protects against C8 discharging through the MCLR pin, and diode D3 enables the capacitor to discharge quickly when power is removed.

Frequency Counter Component List
Resistors (all 1/4W 5% carbon film)
R1,R9 1k (brown, black, red, gold)
R2,R10,R11 470R (yellow, purple, brown, gold)
R3,R13 10k (brown, black, orange, gold)
R4 1M (brown, black, green, gold)
R5 2k2 (red, red, red, gold)
R6,R8,R15 220R (red, red, brown, gold)
R7 10R (brown, black, black, gold)
R12 560R (green, blue, brown, gold)
R14 100R (brown, black, brown, gold)
R16-R23 330R (orange, orange, brown, gold)

Capacitors (electrolytics 2.5mm spacing, others 5mm)
C1,C4,C6 100u electrolytic 16V
C2,C5,C7 220u electrolytic 16V
C3 100n miniature polyester
C8,C11 100n ceramic
C9,C10 22p ceramic

Semiconductors
TR1,TR3,TR4 BC549B npn transistor (or BC547B, 48C etc.)
TR2 BF244A or B N-channel JFET
TR5 ZTX313 npn switching transistor
D1-D3 1N4148 silicon diode
D4 BAT42 Schottky diode
REG1 LP2950 5V regulator
IC1 18-pin DIL socket + PIC16C54 HS/P microcontroller
DISPLAY1,2 0.56" dual 7-segment LED display, common cathode

Miscellaneous
X1 20MHz crystal, HC-49/U case
S1 miniature pcb vertical slide switch, SPDT
INPUT BCN pcb socket
BATTERY PP3 battery snap
4 x rubber feet

Download : source code text file frequency counter / meter schematics PCB Foil Pattern PCB Silk Screen

Source : http://www.apogeekits.com/counter_article.htm

1W Mono Amplifier with IC TDA7052

2008-09-23T10:20:00.000-07:00

This circuit is a 1 watt mono amplifier using the TDA 7052 from Philips. It is designed to be used as a building block in other projects where a battery powered audio amplifier is required to drive a small speaker. It will operate best from 6 – 12 V DC and requires no heatsink for normal use.

Circuit Description :
There are only 5 external components. C1 is the input coupling capacitor, which blocks any DC that might be present on the input. C2 and C3 provide power supply decoupling, and R2 provides adjustable input level. This can be used as a volume control.

Components :
C1 : 2.2uF electrolytic capacitor
C2 : 100nF ceramic/mono
C3 : 100uF electrolytic
R1 : 1K ohm resistor
R2 : 10K ohm log potentiometer
Spindle for potentiometer
TDA7052 Integrated Circuit
8 pin IC socket
Kit 27 Printed Circuit Board

Source: http://www.alltronics.com

Build Your PLL Stereo FM Transmitter With LCD

2008-07-01T01:52:00.000-07:00

Why don't build your FM Transmitter yourself? This Electronic circuit is a stereo FM Transmitter based on BH1415F wireless audio link IC. Phase Locked Loop (PLL) controller use PIC16F628 and the the PLL frequency programming can be displayed with 8x2 and 16x2 LCD. Frequency Range 88-108 MHz

BH1415F can be supplied with 6 - 15V voltage, consumes only around 25mA while providing very sound quality and improved 40dB channel separation. BH1415 is only available in SOP22 IC case and this may be an inconvenience for some folks. On the other hand, because the chip is smaller than regular DIP-based ICs it is possible to fit the entire stereo coder on a small PCB.

Download Documentation BH1415F

BH1415F Datasheet

Source

Phone FM Transmitter

2008-05-19T14:59:00.000-07:00

This FM transmitter attaches in series to one of your phone lines. When there is a signal on the line (that is, when you pick up the handset) the circuit will transmit the conversation. In particular it will radiate from the phone line itself. It is a passive device - there is no battery. It uses the signal on the phone line for power. No aerial is needed - it feeds back the RF signal into the phone line which radiates it in the FM band.

The frequency of transmission may be adjusted by the trimcap. L1 is 6 turns of enamelled wire, L2 is 8 turns and L3 is 6 turns. Spread out L3 coil about 1 mm apart. The coils should not touch. a solder connection (or tap) is required from the top of the first turn in the L3 coil to the pad next to the coil. Solder a piece of wire to the top of the first turn as shown on the overlay. Then solder the other end to the pad immediately next to the L3 coil. R1 & C4 act as a low pass filter. C3 is a high frequency shunt. L2 is a RFC (radio frequency shunt.) It decouples the power and audio from the transmitter amplifier circuit. L1 and C6 should be adjusted to match a frequency on your FM receiver. With C1 at 27p you will find that the kit tunes into the FM band in the 86 - 95 MHz area. With C1 at 22p the band is raised to about 90-95mhz (depending in the coil spacing.)

If you want to move this tunable area still higher to over 100MHz range then replace C1 by a 15pF or 10pF capacitor. You can experiment to get greater transmission range away from the phone line by adding an aerial (about 150 cm of 26 gauge wire) to the collector of T2.

5/8 Wave Tunable FM Broadcast Antenna

2008-05-04T10:55:00.000-07:00

This is a truly professional FM Broadcast antenna, at a hobbyist price that you can afford and is the antenna of choice for the professional personal radio broadcaster! This antenna is a true 5/8 Wave collinear vertical antenna giving you 3.4 dBi gain over the entire FM broadcast band range of 88-110 MHz! What does this mean to you?

That extra "Punch" and extended range you've been looking for! Precision match tuning over the band gives you an exact match to your operating frequency, at a VSWR of less than 1.5:1. This precision match, along with the heavy duty matching coil and durable thick wall aluminum construction provides a maximum power rating of 200 watts That's right, we said 200 watts! Input connection is through a standard PL-259 connector that is sealed inside the mast support pipe. Includes mounting hardware to attach to any mast from1" to 2 7/16". Mechanical assembly is required. If you are serious about your Personal Radio Broadcaster...this is YOUR antenna.

Download 5/8 Wave Tunable FM Broadcast Antenna

Microstepping Driver Kit

2008-05-04T10:32:00.000-07:00

Stepper motors are a dream come true for many hobbyists. They are being used in robots, CNC routers, engraving machines, tilt & pan security cameras, hot wire foam cutters, telescope drive mechanisms and even Halloween animations. This versatile stepper motor driver has been designed to be both powerful and precise enough to work in all of these applications. It uses the Allegro/Sanken SLA7062M IC which combines low-power CMOS logic with high-current, high voltage power FET outputs. It is capable of handling motor winding currents of up to 3 AMPS per phase and it operates from a single supply voltage of 10-40 volts DC.

The microstepper drive works with any unipolar (6-wire) motor. Unlike traditional “R/L” unipolar drives that use power wasting series resistors, this circuit uses a Pulse Width Modulated "chopper" drive to deliver maximum power to your stepper motor with no dropping resistors. The motor current is fully adjustable from 500 mA to 3.0 Amps with an onboard potentiometer. The circuit also has an automatic current reduction feature that reduces motor current by 50% when the motor is idle for more than 2 seconds.

The drive accepts simple STEP & DIRECTION signals. The input signals are fully opto-isolated and can be easily interfaced to any control source including a Microchip PIC, an Atmel AVR or a PC parallel port. The input signals are directly compatible with all of the major CNC software packages when used with a PC parallel port. Two onboard jumpers allow you to select between half-step, quarter-step, eighth-step or sixteenth-step resolution.

This is a high performance microstepping drive for use with high torque stepper motors.

FEATURES:

* Dimensions - L: 4" W: 3" H: 2".

* Requires 10-40 Volt DC power supply.

* Selectable: half-step, quarter-steo, eighth-step or sixteenth-step.

* Idle current reduction: reduces motor current by 50% when idle.

* Internal 5V regulator onboard (No separate 5-volt supply required).

* Maximum step rate is over 200 kHz.

* Motor types: Works with all 6-wire unipolar. NEMA 17, 23 or 34 sizes.

SLA7062M data sheet: download

Advanced LCD Satellite Tracking Interface

2008-04-24T03:40:00.000-07:00

Project PCB was designed on a PTH PCB measuring 5 x 10cm. Interface supports Server Easycom and Yaesu GS-232.

The Satellite Antenna Tracking Interface is targeted to interface Yaesu rotators to your PC running either a NOVA for Windows or SatPC software.

Project uses LTC1298 SOIC 12bit A/D chip and a PIC16F84A. SMD chip (LTC) will be supplied pre-soldered on all kits and assembled. Interface takes its power from Yaesu Controller. A Free DIN8 Plug is supplied with kits/Assembled.

A few, fully assembled & tested units are being offered at the moment followed by kits getting ready within a month.

Dowload Project Documentation Visit Page

100w LCD PIC16F88 SWR Meter for VHF- UHF

2008-04-24T03:04:00.000-07:00

This SWR Meters uses PIC16F88, which built in RC osclillator running at 8 MHz. Micro controller calculates forward and reflected power and in addition to FWD and REF readings on 2x16 LCD, cotrols LCD back light.

The very basic purpose to make this project is to encourage radio amateurs to build their own High Quality LCD SWR Meter at low price, instead of buying expensive ready made units.

Project is developed on two double-sided PTH boards. The first one CPU board where LCD, Regulator, and Op.amp are located. This board receives pure DC Level from sensor board for calculation and display. The Second board is RF Sensor Bridge where power from your transceiver comes in and goes out to antenna. Its strip line type pickup and uses SMT parts, including BAT85 diodes.

Download Project Documentation Visit Page

High Gain TV Antenna Boosters

2008-04-20T23:58:00.000-07:00

This is a small, broad band, signal Antenna boosters which covers the frequencies from 40 to 900 MHz. These frequencies include TV in VHF and UHF and also the radio broadcasting frequencies in the 88 - 108 MHz FM band. It is connected between the antenna and the input of your receiver and boosts the signals by up to 20 dB, thus making it possible to receive even the weakest signals.

Technical Specifications
Frequency range:	40-860 MHz
Signal gain:	15-22 dB
Input/output impedance:	75 Ohm
Working voltage:	9-18V DC
Power Supply:	9V battery
Board Dimensions:	41x55mm
Board Connections	Solder Posts

How The Antenna Booster Works
The circuit is built around a single transistor a UHF low signal device, the BFW 92. This transistor can operate in frequencies as high as 1.6 GHz, and has a gain of 23 dB. The signal from the antenna is applied to the input of the circuit and through C5 is fed to the base of the transistor. It is amplified and from the collector of the BFW 92 through C2 and C1 is taken to the input of the radio or TV receiver.

The circuit operates off a small 9 V battery which, because of the very low power
consumption of the circuit, is going to last for a very long time.

Download User Manual with schematic. Visit page

Audio Frequency Function Generator 20Hz - 20KHz

2008-04-20T23:37:00.000-07:00

This is an AF function generation covering the frequencies between 25-25,000 Hz in three bands. It has sine, square and triangular saw tooth outputs and has sufficient output to drive any amplifier and low distortion to be useful in high precision measurements.

Freq. response:... 25-25,000 Hz (three ranges A, B, C)
Range A:..25-250 Hz
Range B:..250-2500Hz
Range C:..2500-25,000 Hz
Distortion:..0.5 % (Max.)
Output voltage:..10 V pp Sine & Triangular
16 V pp Square wave
Output impedance:... 600 ohm

How it Works
The frequency generator uses an IC the TL082 which is a dual op-amp to produce the basic
waveforms. The first of the two op -amps in the IC is used as an oscillator the frequency of
which can be set by means of the potentiometer P2 and its range depends on the value of the
capacitor C3 and is selected by means of S1. The trimmer P1 is used to adjust the duty cycle
of the oscillator. The second op-amp is an integrator which converts the triangular wave form
that is produced by the oscillator to a square one. P4 is used to adjust the amplitude of the
signal. P3 is used to adjust the amplitude of the triangular waveform.

The signal from the output of the oscillator is taken to the circuit built around the two transistors to be converted from triangular to sinusoidal. The two trimmers P5 and P6 are used to adjust the shape of the positive and negative portions of the signal for the best symmetry a nd minimum distortion and P7 is the potentiometer which adjusts the output level for this waveform. As you see the circuit consists of fairly basic building blocks with independent adjustments for every one of them which makes a very versatile and easy to operate instrument. The power supply is also incorporated on the circuit board and you only have to connect 24 VAC across the rectifier bridge to make the circuit work.

Download User Manual with schematic. Visit page.

Square Wave Oscillator 1Hz - 100KHz

2008-04-20T23:26:00.000-07:00

A square wave generator is one of those pieces of equipment that has many uses in the workshop yet few hobbyists actually have. This simple kit, based on the popular 555 timer IC, generates six preset frequencies from 1Hz to 100khz. It has a wide operating voltage range and even provides visual indication of the output.

Easy-to-build kit generates six square waves of 1Hz, 10Hz, 100Hz, 1KHz, 10KHz & 100KHz output frequency using the onboard jumper selectors.

Ideal for the DIY test bench or school teaching project.

The kit is constructed on a single-sided printed circuit board (PCB). The PCB measures 78 x 50mm and will mount on a small Plastix “Jiffy” box. Protel Autotrax & Schematic were used to design the PCB.

Download User manual with schematic. Visit page.

FM Telephone Transmitter

2008-04-20T23:19:00.000-07:00

This miniature transmitter attaches in series to your telephone line, transmits the conversation to an FM receiver. Tune to a clear spot in the FM band of your radio. Completely parasitic; i.e. uses the power from the telephone line and needs no battery. The circuit might be used to share or record conversations, but not intended for illegal use.

Specifications:

* L: 1-3/4" W: 3/4" H: 1/2"
* Powered by phone line.
* Uses phone line for antenna.
* Transmission frequency is user selectable.
* Transmission can be listened to on any FM radio.
* Includes alligator clips for easy connection to phone line.

Download Manual for complete details, including schematic and theory of operation. Visit page.

Wide Band Synthesised FM Transmitter

2008-04-20T23:07:00.000-07:00

Phase-Locked Loop (PLL) based crystal-locked wide band synthesised FM transmitter delivering a high quality, stable 10mW output. Accepts both MIC audio signal (10mV) and LINE input (1v p-p) for example hi-fi, CD, audio mixer (like kit 1052) or computer sound card.

The Radio Frequency (RF) output circuitry includes a three-pole filter for reduction of harmonics and other spurious signals. The spurious output signal level is better than -40dBc (0.0001 times the power of the wanted signal level), which makes the project suitable for driving an external power amplifier.

It delivers up to 10milliwatts of RF power to the antenna which can be a simple single wire about 74cm long (or open dipole or ground plane). Output power can be boosted to 250mW when used with our FM Power Amplifier.

Ideal project for the beginner who wants to get started in the fascinating world of FM broadcasting. See documentation link below for full details.

The transmitter is powered from a 12v supply, but it will operate from 9 Volts to 16 Volts. Please note that most standard DC mains adaptors are unsuitable for powering FM transmitters as they introduce an intolerable level of mains hum.

Download Manual 1 2 with Schematic and parts list. visit page

FM Transmitter With 9 Volt Battery

2008-04-20T22:43:00.000-07:00

This new FM Transmitter Kit can transmit over 900 feet in the open depending on aerial used with 9 volt battery. The tank oscillator coil is built into the circuit board, and has been tinkered with to give the best distance and stability for it's size. The battery supply rails have been well tied together with respect to radio frequencies.

The tracks are also thicker making the fm transmitter circuit a single ‘solid’ block eliminating RF currents in different parts of the circuit. This also means the battery no longer has RF on it which makes the whole unit a lot more frequency stable. Can be tuned anywhere in FM band.

Specifications:
* L: 1-3/4" W: 7/8" H: 1/2"
* Requires 9 Volt Battery
* Transmission frequency is user selectable.
* Transmitter can be listened to on any FM radio.

Download kit manual for complete details, including schematic and theory of operation. Visit Page

AM1C - Entry Level AM Radio Transmitter Kit

2008-04-20T22:39:00.000-07:00

#1 Scouting Project For Years

* Tunes entire 550 to 1600 KHz AM band
* Operates on 9 to 12 VDC, includes case set
* Standard line level input with RCA phono jack
* 100 mW output. Range up to 1/4 mile under optimum conditions

The AM1 is a great first kit, and a fine low power AM broadcaster for the hobbyist on a budget. It's a great way to learn the basics of AM broadcast technology, not to mention basic soldering and component identification (if you're a beginner!) The transmitter can be tuned to broadcast anywhere in the AM band (550 to 1600 kHz). Setting frequency is simple - tune a nearby AM radio to the desired frequency, then adjust the AM1 coil to match the radio. With 100 mW of output power, range can be up to 1/4 mile. The AM1 has been used by Scout camps, churches, schools, and other organizations to provide easy and low cost communications.

Note: The AM1C is a do-it-yourself learning kit that you assemble. The end user is responsible for complying with all FCC rules & regulations within the US, or any regulations of their respective governing body.

Download AM1C Manual Visit Page

AM25 - Professional AM Transmitter Kit

2008-04-20T22:31:00.000-07:00

Synthesized Professional Quality for your AM Station!

* Fully synthesized, no frequency drift!
* Ideal for schools
* Microprocessor controlled
* Strappable for higher power output where regulations permit
* Includes AC power adapter and case set

Run your own AM radio station!
The AM25 operates anywhere within the standard AM broadcast band, and is easily set to any clear channel in your area. The design is similar to that of a commercial radio transmitter, so you'll learn how the "big guys" operate. It is widely used by school - standard output is 100 mW, with range up to 1/4 mile, but is jumper setable for higher output where regulations allow. Broadcast frequency is easily set with dip-switches and is stable without drifting. The transmitter accepts line level input from CD players, tape decks, etc. Includes case & knob set & AC power supply.
Note: The AM25 is a do-it-yourself learning kit that you assemble. The end user is responsible for complying with all FCC rules & regulations within the US, or any regulations of their respective governing body.

Download AM25 Manual Kit Visit Page

RF Power Amplifier for iPOD Stereo FM transmitters 1W

2008-04-19T02:44:00.000-07:00

The schematic show you a RF amplifier with very high gain. The feeding RF signal enter C9 to transistor Q1 which has a self biased working point. The gain and working point is set with the two resistors R1 and R2. FB1, C5, C6 works as filter for rejecting RF to power line. Q1 has a gain about 15dBm. The output signal can be found a the collector which then enter a second amplifier stage Q2. This stage also has a self biased working point. The gain is set by the resistors R3//R4 and R5//R6.

Why do I have 2 parallel resistors like that?
It is because I want to be able to change the gain of the amplifier. On the PCB below you will see that I only have 2 pads for the resistors. When I want to resistors I solder the two resistors R5 and R6 on top of each other and the same with R3 and R4.

I advice you to start building without R3 and R5 and test the unit. If you want you can then add R3 and R5 later to obtain max gain of this stage.
Q2 has a gain of 12 dBm. FB2, C7, C8 works as filter for rejecting RF to power line.

The last amplifier stage is based around the transistor 2N3866. This transistor has low input impedance.
I match it by using 2 capacitors (C11, C12) and the inductor L1 to about 50 ohm. The transistor has an output impedance match, (C13, C14, and L3) to get best performance for an 50-75 ohm antenna.

# The inductor L1 is made by a wire 2 turns with 5mm diameter.
# The inductor L2 is made by a wire 7-9 turns with 6.5mm diameter.
# The inductor L3 is made by a wire 4 turns with 6.5mm diameter.

L4 is a Axial Lead Bead, which reject RF very good and has low resistance. You can use almost any choke or large inductor for L4, it is not a critical component.
The FM transmitter require 2 AAA batteries and consume about 38mA.
To get rid of batteries, I have added a voltage regulator IC1, to the PCB which deliver 3.3V to the FM transmitter unit.

PCB
The PCB is mirrored because the printed side should be faced down the board during UV exposure.
To the right you will find a pic showing the assembly of all components on the same board.
This is how the real board should look when you are going to solder the components.
It is a board made for surface mounted components, so the copper is on the top layer.

Grey area is copper and each component is draw in different colours all to make it easy to identify for you.
The scale of the pdf is 1:1 and the picture at right is magnified with 4 times.
Click on the picture to enlarge it.

Important:
Remember that the case of the Q3 is the collector and has direct connection to +12V DC.
This case must NOT come in contact with the ground plane (GND) or any order parts of the PCB.
At the right photo below, you can see that I have soldered Q3, 3-5mm above the ground plane.

Preparing BCP for transistor Q3:
The picture below show a vertical cut through the PCB.
Here you can see the Top side which has the strip line connections to all the parts and to the transistor legs Base and Collector.
You can also see the ground plane on the other side of the PCB.
After I have drilled the thin hole for the transistor legs, I use second larger drill (3mm), and drill a little bit into the ground plane.

The larger 3mm drill remove the copper around the hole and you will have no electric contact between the ground plane and the legs of the transistor.
The procedure must be done for both the Base-leg and the Collector-leg. Since the Emitter-leg is already connected to ground, this hole doesn't need to be modified.
As you see of the picture below, the transistor leg is connected (soldered) to the pad, but the leg has no connection to the ground plane.

Soldering and testing:
The soldering of this unit is pretty basic.
Connect all parts and make sure you have no soldering bridges on the PCB. soldering wick and rosin are good tools to have handy while soldering.
When testing the amplifier I advice you to use a 50 ohm dummy resistor as load or a proper antenna (more info about antenna below).
Make sure you use a non-inductive resistor. Before you switch on power you should set the variable capacitors C13 to max capacitance and C14 to min capacitance.

DC testing:
To make sure that both transistors Q1 and Q2 has good working point I advice you to measure the DC voltage at the junction R1 - FB1 and R4 - FB2.
I measured with NO input RF signal:

DC volt FB1 = 3.7 to 3.9 V
DC Volt FB2 = 7.1 to 7.4 V

Now your unit is ready to be tuned for best performance!

Download : Project Documentation External Antenna

PLL FM Transmitter

2008-04-19T02:29:00.000-07:00

Dual-speed PLL designed for wideband FM transmitter.

Power supply: 8-15 V stabilized, 40 mA
Frequency range: 82,5-108 MHz
Step frequency: 100 kHz
RF input voltage range: 10-500 mV
RF input impedance: 135 ohm

Parts list:
Capacitors:
C1, C12 - 2,2 nF (ceramic)
C2, C9 - 10 nF (ceramic)
C3 - 47 uF (electrolytic)
C4 - 10 uF (tantalum)
C5 - 0,47 uF (electrolytic)
C6, C11 - 100 nF (ceramic)
C7 - 1 nF (ceramic)
C8 - 220 uF (electrolytic)
C10 - 22 pF (ceramic)

Resistors:
R1 - 1k
R2 - 4k7
R3, R4, R5, R7 - 10k
R6 - 1k (optional)
R8 - 47k (optional, see below)

Misc.:
IC1 - SAA1057
IC2 - PIC16F84 (programmed) + socket
IC3 - 78L05
X1 - 4 MHz crystal
D1 - LED diode (optional)
Tl1 - button (optional)
jumpers or DIP switches

Software for the IC2:
pll16f84.asm, pll16f84.hex. Oscillator type: RC, watchdog: ON.

Jumpers/DIP switches setting: see project documentation or download user-friendly program!

Instructions

The Tl1 button resets the unit. Press it after frequency set. The unit provides a reset on power-up, so you don't need to use the button.
The D1 LED indicates the tuning cycle is done (after one second from reset). It's not needed to use it and the R6 resistor.
The R8 resistor provides a minimal voltage of about 2 V on the PLL output. Use this resistor if the transmitter's oscillator doesn't work if the tunning voltage is below this value (mainly after power-up). Place the resistor over the R3.

Notes:

* Output of the PLL should not be directly loaded with big capacities (over about 0,3 uF). The PLL loop may be unstable. This applies to some unknown transmitters.

Download Project Documentation