Wolfden Press Electronics

Electronics Projects from Wolfden Press

Some of these projects were gleaned out of my own experimentation while others are built from available kits.
Click most images for a schematic drawing of the circuit in PDF format.

Try the Capacitance Converter at the bottom of this page.

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Projects List

Click for alphabetical list of the projects.

Gauss Meter

Wind Meter

Infrared Tachometer

Function Generator/Frequency Counter
(Oscilloscope Traces)

Audio Visual Bat Detector

Digital Volt/Amp Meter

Stroboscopic Tachometer

Programmable Counter

Function Generator

Bat Spy (Recorder)

Three Digit Counter

Pulse Width Modulator

Crystal Tester (Transistor)

Ultra/Audio Tone Generator

Strobe Light/Siren

Transistor Tester

Magic Conjuring Board and Magic Wand

Bat Call Simulator

1.25-30 VDC 3 Amp Power Supply

2 Amp Power Supply

1.5 Amp Power Supply

The Bat Listener

Lux Meter

Model Train Throttle

30 Watt Stereo Amplifier

Infrared Detector for a Model Train

Heterodyne Bat Detector

Derek's Train Sounds

NE555 AF/RF Generator

FM Transmitter & Receiver

Crystal/Oscillator Tester and
Frequency Counter
(Oscilloscope traces of crystal & oscillator)

LC Meter

Zener Diode Tester

Digital Oscilloscope

Programmable Counter

Function Generator II

Wildlife Listener

3 Watt Audio Amplifier

Tube Amplifier Circuits

Tube Tester Schematic

Capacitance Converter

Here is an alphabetical list of the projects.

= back to Projects List

gauss

Gauss Meter
After some tedious work on the breadboard I finally got my Gauss meter to work just right. It measures from 1 to 1,999 gauss. A red LED indicates the north pole of the magnet being measured and a green LED shows the south pole. (See the schematic for details.) The gauss meter is built around the A1302 Linear Radiometric Hall Effect Sensor with a LM358 Op Amp to drive the LEDs and a 200mA digital panel meter for the readout. The meter reads minus (millivolts/gauss) for north pole and plus for south pole.

Glick here for the inside view.

wind

Wind Meter
The Wind Speed Meter is an electronics kit construction, built around a
programmable micro-controller PIC16F628-20. A pair of 40KHz sensors are
mounted on a "sensor handle". A signal is sent between the two sensors
and the change in frequency, caused by the wind, is detected and displayed as wind speed.

The kit for this project is available from Carl's Electronics (as Ultrasonic Wind Speed Meter Kit).

tach

This is my Infrared Tachometer. It will read the RPM of almost anything that turns. However, It is not a complete tach in itself as it needs a means to display the RPM. For this, the alligator clips are connected to a frequency counter or the frequency input of a multimeter.

tach

Here is the inside of the tachometer. You can see that it is quite an uncomplicated arrangement. The IR is transmitted from the IR LED, bounced off the rotating object and the reflection is received by the IR sensitive photo-transistor. Frequency X60=RPM.

freqctr

My Function generator/Frequency Counter was built by combining two kits. The function generator is a kit from Jameco Electronics and the frequency counter is a kit from CallSaver Corp. It measures from 1 Hz to 50 MHz.

The schematics are in two parts - Function Generator, click image.

frqfct

With the inside view you can see the two circuit boards and the controls. The power supply, controls and enclosure are supplied by me. The 9 volt battery powers only the frequency counter so it can be used portable (as with the IR Tach above or the Strobe Tach below).

For the schematic of the Frequency Counter click image.

Here are a few oscilloscope traces of the three waveforms output from my functionn generator.
(These were read at a frequency near 20 KHz.)

sine

Sine Wave

tri

Triangle Wave

square

Square Wave

el-av

A/V Bat Detector
My audio/visual bat detector. With this gadget you can hear the bat call
and see the flashing LEDs at the same time. When a bat call comes in,
the LEDs will light relative to the frequency received. One LED = 20KHz,
eight LEDs = 80KHz.

avocet

AV Bat Detector Circuit Board
The circuit board is wired on the top surface (because I build most of my projects only once, I use copper clad project boards instead of printed circuit boards) with some lands and buss connections of the under side. The audio section is on the green board and the video on the brown board.

el-v/a

Volt/Amp Meter - Label awaiting final assembly

Here is a volt/amp meter built with four seven-segment LED displays and driven by a ICL7107 A/D converter. This is my first project using LED displays. I used the 7107 datasheet as a guide and added a few components for reading volts AC and Amps. The -5v is supplied using a ICL7660 voltage converter.

v/a-ct-bd

V/A Meter Circuit Board

Here is my V/A Meter circuit board. The ICL7107 takes most of the space but there are only a few resistors and capacitors along with the 7805 regulator and the 7660 voltage converter. The gray ribbon wire goes to the 7 segment displays.

Click image for the schematic in PDF format.

bather

This one, I call my Stroboscopic Tachometer. The circuit design
is not mine but the project is. The strobe flashes on a rotating
object and the RPM can be read by adjusting the dial. With an
accuracy of about 10% the ranges are 150 to 1700 RPM and
850 to 9000 RPM.

Click Here for the schematic of this project (pdf).

bathet

The bright, white LED is mounted in a 3.5mm phone plug so I
can use an extension cable for hard-to-get-at places. Also, a
jack on the side provides access for reading the frequency
directly with a frequency meter, an oscilloscope or a multimeter
that has freq. feature. This method improves the accuracy to
about 1 percent.

Click Here for the schematic of this project (pdf).

4dig

Programmable Down Counter

My down counter can be starter with any number from 9999.
When started it will count down to 0000 which triggers the alarm
piezo buzzer. The circuit design is not mine but the project is.
The kit number CK1613 (DIY Kit 154) that I built for this project
was from Carl's Electronics.

Click Here for the description of this kit at Carl's Electronics in Oakland, CA.

4dig-in

Inside the Counter

The green pc board is the counter which includes the set
and increment buttons. The brown circuit board is my
one second clock and alarm, both built using 7555 timer ICs.
The timer will operate with the 9 volt battery or a wall adapter.
The circuit draws only 20mA.

Click Here for the schematic of the 1 second clock and alarm circuit (pdf).

bather

Function Generator
This was the first Function Generator I built based on the XR-2206 IC. I learned about wave shapes and frequencies by using this with my oscilloscope. I liked this one so much that I built the Function Generator/Frequency Counter shown above.

Click image for a larger view.

For the schematic see the Function Generator above.

bathet

Bat Spy (Recorder)
Bat Spy is not actually used to spy on bats but rather to record their chirps and buzzes while using a bat detector. It is built using a 20 second (pre-built) digital recording module with the push-buttons, microphone, speaker and LED added. To record bats I hold it near the speaker of my bat detector and press record. It will playback through the speaker or directly into my computer audio analyzer program.

Click image for a larger view.

3dig

Three Digit Up Counter

My three digit counter will count up from 000 to 999
in 1 second intervals (the equivalent of 16.6 minutes).
It is handy for timing the duration of certain projects such
as: how long have I been sanding this paddle?.

3dig-in

Inside the Counter

The circuit for this counter is based on the MC14553, a 3-digit BCD
counter and the MC14543, a BCD-to-7-segment latch/decoder/driver.
The one second clock circuit in this counter is a modified
version of the clock circuit in my four digit counter.

Click Here for the schematic of this counter (pdf format).

bather

Pulse Width Modulator
This is my Pulse Width Modulator demonstrator.The square wave it puts out is adjustable in duty cycle from 10% to 90% with a frequency of 1200Hz and an a 8 vdc output voltage. It will drive a small DC motor. The one I used came from a dismantled printer. It turns between anout 10 and 750 RPM. The varying pulse width output can be seen on an oscilloscope as the speed is increased or decreased.

Click image for a larger view.

Click Here for the schematic.

bathet

Crystal Tester
The crystal tester shown here is built with a two transistor circuit. It is used for testing the type of crystals found in RC models, etc. The green LED will light up if the crystal under test is oscillating. Also, there is a output jack so the frequency of the crystal can be read on a frequency counter or an oscilloscope. The npn transistors are not critical but they need to have a hFE (current gain) of about 200.

Click image for a larger view.

Click Here for the schematic.

ultra

Ultra/Audio is a tone generator that operates through the audio frequency range and into the ultrasonic, 50Hz to 45KHz.
The "sound" can be heard from the piezo speaker (at low frequency)
or with a bat detector. It can also be measured with a
frequency counter or an oscilloscope.

tach

The Ultra/Audio circuit operates on 18 volts (2 - 9V batteries). The frequency adjustment is a ten-turn pot that allows for fine tuning. The output is selectable for "Low" 50Hz to 2500Hz, and "High" 2200Hz to 45KHz. The output is either a triangle or a square waveform.

ultra

Here is another strobe project, but this one flashes 16 ultra-bright
LEDs and has an audio section to produce a siren effect.

Click makes image larger

tach

The circuitry for the Strobe/Siren is based on 4 ICs. Flash rate
and duty cycle for the LEDs is adjustable, as is the siren level.

Click image for a schematic in PDF format.

ultra

Transistor Tester. My transistor tester helped me identify
a multidude of transistors that were salvaged from a
variety of junked electronic equipment.

tach

Transistor Tester Inside. The components are rather hard
to see but they consist mainly of a couple of transistors, resistors,
switches, a speaker and battery. Click to see schematic.

magic

Magic Conjuring Board with Wand

I found the circuit for the Magic Conjuring Board on the DIY Electronic Projects website (the Magic Wand Conjuring Trick by Rev. Thomas Scarborough). My circuit differs in that I have added the timer and decade counter ICs, and 10 LEDs to flash in a circle and a piezo speaker for sound effect. When the right combination of buttons is passed over with the magic wand the LEDs (red, white and blue) flash around the circle and the buzzer sounds.

Click image for a larger view

u-magic

Under the Conjuring Board

When the magic wand (with a magnet imbedded in the end) passes over reed switches S4, S5 and S6 (see Schematic) in that sequence, it makes the output of the CD4081 high which turns on the transistor that feeds power to the LED circuits. S1, S2 or S3 will turn off the LEDs if passed over at any time. The reed switches can be placed at any location under the board that will make the conjuring trick interesting.

Click image for a larger view

bread

Breadboarding the Conjuring Circuit

After much experimentation with component values I finally got the circuits to operate well. The CD4081 is a Quad AND gate which turns on/off depending on which inputs are high and low. The CD4093, a Quad NAND gate, functions as a clock to drive the LED circuit at 15Hz and the piezo speaker at 460Hz. The CD4017 is a decade counter. It drives the LEDs in their flashing sequence. The complete circuit draws about 5mA in standby and 15mA operating.

Click image for the schematic

ultra

Bat Buddy produces a kind of simulated bat sound
in ultrasonic, a series of clicks at 40kHz that can only
be heard with a bat detector.

tach

Inside Bat Buddy is an IC that generates three
frequencies which are then mixed in a binary divider
and amplified for the 40kHz output transducer.

ultra

Power Supply
This is very useful when working on projects.
It supplies voltage from 1.25 to 30 VDC at up to 3 amps.

tach

Power Supply Inside
The voltage adjustment is made through a LM723 voltage
regulator and the output is through a 10 amp MJ3001 Darlington
Transistor. The analog V and A meters are direct coupled.

ps2

2 Amp Power Supply
Here is the same power supply as above, built in a smaller package. This one has digital panel meters. The schematic for the main power is the same as the power supply above so I did not redraw it here. The meter operation is quite different. It supplies voltage from 1.25 to 30 VDC at up to 2 amps. Here it reads 10 V at 200 mA with a 50 Ohm load connected.

Click image for the meter power schematic

ps2in

2 Amp Power Supply Inside
The power supply in this enclosure becomes quite compact. The digital meters are shown with their scaling resistor circuit boards attached. The batteries provide power for the meters. They are switched on with the small relay just above the transformer.

Click image for a larger view

ps1.5

1.5 Amp Power Supply
And yet another power supply. When I built the 2 Amp power supply I inadvertently applied the incorrect voltage to the meter terminals, frying it. I bought two more meters and ended up with one extra. So this PS came out of the extra meter. This uses a LM317 adjustable voltage regulator so the circuit uses few parts. The power transformer is a desk-top power supply from a printer - its output is 24vdc at 1.5a.

Click image for the schematic

el-bat-list

The Bat Listener
I call my new bat detector The Bat Listener. It is a heterodyne, using ideas of two other designers. The pre-amp, mixer and output are from the Tony Messina Bat Scanner and the local oscillator from a circuit by Bertrik Sikken. After prototyping and testing I came up with a good working (manual tuning) bat listener. The sensitivity almost equals the Bat Scanner with minimal background noise. The enclosure was once a printer power supply.

luxe

Lux Meter
I decided to replace the #1141 bulbs in my travel tariler with leds, to reduce battery drain. I built one with 24 warm white 17,000 mCd leds, I needed a light meter to measure the luminesance of the bulb vs. the leds. This project, I built from my electronic junk boxes. The meter is from an old SWR meter and the solar cell was once part of a camera light meter.

Click image for a larger view.

tach

Lux Meter Circuit Board
The circuit is straight forward, using a LM324 Op-Amp as a current amplifier, some resistors, a voltage regulator, and a couple of switches. It reads from 10 lux, a dimly lit room, to 100,000 lux, almost direct sunlight. The voltage regulator is to maintain 5 volts in the circuit and the trim pot is for meter calibration. I borrowed an accurate foot-candle meter to do my calibration.

Click image for a schematic in PDF.

thro

A DC power controller for model railroad. This one is built
around a LM350K 3 Amp power voltage regulator.

thro

Inside the train controller (a bit of a rat's nest).

thro

This project is a Stereo Amplifier that I decided to build from several kits. It performs very well with a tape deck and with a record turntable. The output sound is best with a good pair of 4 Ohm speakers.

Click this image shows a schematic of the power supply, power amp and the LED VU meter.

thro

Inside the stereo amp is the power amp, a Velleman Kit K4003, the LED VU meter, a Velleman kit K4305 and the tone/volume control, a Kemo Germany kit #18-192. The preamp uses a TL082 dual op-amp and was home built.

Click this image shows a schematic of the preamp and the stereo tone/volume control.

rr-ctrlr

My Model Railroad is an "N" scale layout called "The Kamloops Line". You can see the track plan in this picture. The 14 turnout switches are used to change the route a train takes. Red or green (bi-color) LEDs show the position of the turnout. Other controls are for lighting, accessories and Digital Command Control.

The complete layout can be viewed on my www.sashart.org website.

irdet

This little circuit is a Infrared Detector. It includes LED flasher and bell circuits and was built to operate the grade crossing lights and bell when the train rolls by. The transmit and receive circuits are from a Jameco Electronics kit (the ir transmit circuit in not shown here). I added the 5 volt regulator components and the relay, and built the flasher for the crossbuck lights. The bell circuit is at the upper left.

Click image for schematics in PDF

cx1

I built my crystal tester to test some crystals and can oscillators which bounced around in my parts box for a long time. The frequency counter in this project displays the frequency for the crystals and oscillators and also functions as an independent frequency counter. Its range with the prescaler circuit is from 10 Hz to 600 MHz. The counter section is built from a kit by DIY Electronics.

Click image for a larger view.

cx2

Inside the crystal/oscillator tester, the circuit is quite simple. The crystal test is built around a MC14060 binary counter IC shown in the left side of the picture. The frequency counter PCB is at the top right and the rest is switches and the sockets for the can oscillators. The circuit will operate from the 9 volt battery or a 6 - 12 volt wall adapter. It draws 12 mA on standby and 35 mA on test.

Click image for a schematic drawing in pdf format.

cx2

Here is an oscilloscope trace from a can type oscillator. (It can be seen on the tester in the above picture.) The frequency read here is 11.289320 MHz.

cx1

This trace, also read from my crystal/oscillator tester, is a crystal similar to those used in r/c transmitter/receivers. This one is being read at 5.767680 MHz.

bather

Larry's version of the Heterodyne Bat Detector.
This one works like an AM radio except that it receives
bat calls instead of music.

Click makes a larger image

bathet

Inside the Heterodyne Bat Detector
Go to Bats of Williams for more of
Larry's bat detectors and other batty stuff.

No schematic for this one

dtr

Derek's Train
This one is for Derek. It has three train sounds,
a whistle, bell and the clackity clack of the railroad track.

Click image for a schematic drawing.

sqwave

AF/RF Generator
Here is my square wave AF/RF generator. It is made
with a NE555 timer IC and produces a frequency from
65 Hz to 75 KHz.

Click image for a schematic drawing.

fmtr

FM Transmitter
Here is my FM stereo transmitter. It connects to the audio out jacks on my TV and transmits the sound to my FM receiver for personal listening. This one is built from a kit available at Jameco Electronics.

Click image for schematic drawing in pdf.

fmrec

FM Receiver
The FM receiver was built from a Ramsey kit. It is a perfect companion to my FM Transmitter and has enough power to drive a good size speaker but it works well with an earphone. It operates on a 9 volt battery or a wall adapter.

Click image for a schematic drawing in pdf.

L/C Meter
Some of the frequency oscillators I build require very small value capacitors and inductance coils. I bulit this Inductance/ Capacitance Meter from a kit available at DIY Electronics. It is built using a 16PIC16F628 Microcontroller and has autoranging. The inductance range is from 10nH to 100mH and the capacitor range is from 0.1pF to 900 nF.

Click image shows the circuit board and inside view, and here for the schematic.

zen-test

Zener Diode Tester
Some of the diodes in my parts box are really zeners (without identifying numbers). In order to find out the breakdown voltage of these, I built a Zener/Diode Tester. It uses a 9 volt AC transformer (in reverse) and a NE555 timer IC. Also, a volt meter. The zener tester will also test regular diodes. I used the same enclosure as the LC Meter.

Click image shows the circuit board and inside view, and here for the schematic.

d-scope

Digital Oscilloscope

This is my Digital Oscilloscope. Here it is reading a 1KHz sine wave signal from my function generator. It comes as a Kit from CanaKit, Model #DSO 062 at: Canakit.com. Details and specifications can be found on the JYE Tech website at: JYETech.com It is small (pocket size) and has a 2" screen. This little scope works quite well for its size. It will measure up to 1MHz on the scope and 5MHz on the frequency counter. The kit does not come with a case, I added that. Inside is a frequenzy divider that is configured to divide by 10 or 100, allowing me to read frequencies up to 100MHz on the scope and 500MHz on the frequency counter.

Click image for a larger view.
Click here for the Frequency Divider wiring drawing in pdf format.

func-gen

Function Generator II

My new Function Generator was built as a complimentary to the Diggital Oscilloscope. Based on the XR2206 IC, it is essentially the same circuit as the one near the top of this page but it's in a more compact package. I pushed the 2206 to almost 2MHz. It has Sine wave, square (sync out 1/2 and full swing, and triangle wave output. Amplitude on the sine and triangle is variable, 0 to 4 volts and on the square is 2 volts, 1/2 swing and 4 volts at full swing. Power is supplied with a 12 VDC wall pack.

Click image for a larger view.

listener

The Wildlife Listener is a high gain audio amplifier. It's great for listening to bird songs and other interesting critters.

listener

Inside the wildlife listener are two integrated
circuits, an LM1458 op-amp and an LM386 amplifier.

listener

Here is a handy little audio Amplifier that puts out 3 watts of power. After building it with 4 tarnsistors I added a preamp using a TL074 op-amp. See schematic.

This was one of the first schematic drawings I made of the amplifier that I wanted to build. The power supply is not shown but eventually, I found another plan. I had lots of parts and boxes full of tubes so I felt that I could build just about anything.

Click image for a larger drawing in JPEG format.

tubeamp

Here is the schematic of the first stereo amp that I built, in the early 1960s. (The original drawing is too light to scan, so I did a redraw with Design Works.) Most of the parts were salvaged from discarded TV and radio chassis that I found behind repair shops. They were happy to have me take them away. I listened to my first Stereo records with this amp and was thrilled with the sound.

Click image for a full size drawing in PDF format.

tubeamp

This schematic is for a Vacuum Tube tester. As I was fixing lots of TVs, and the tubes were most often the culprit, a portable tester was very handy. So, I borrowed the manual, copied the schematic, and built my own. It worked great for many years. That is, until transistors and integrated circuits took over.

Click image for a full size drawing in PDF format.

unit-conv