Some PDF's have PCB's generated for the circuit ready for construction.
Do check the scale of the drawing after you have printed it out.

Designs are available as GIFs and PDF's.
To open the simulations you will need Crocodile Clips v3 or 4 or LiveWire.

This page is currently being updated. Bold links in capitals lead to new pages for faster viewing of circuits. All circuits will be completed as time allows.

On this page...

555 SIREN GENERATOR
A simple design from 2 555 timers - this is versatile and loud. - NEW

AUDIO AMPLIFIER: PRE-AMP
A low signal pre-amp using an op-amp from a single battery supply - -

AUDIO AMPLIFIER: BRIDGED 20W 12v
A common amplifier based around the TDA2005 IC.

AUDIO AMPLIFIER: 7W
A simple circuit based around LM383 - NOT TESTED

AUDIO AMPLIFIER: 14W
Single supply and split supply versions of the popular TDA2030 amplifier

AUDIO AMPLIFIER: 32W
Single supply and split supply versions of the popular TDA2050 amplifier

AUDIO AMPLIFIER: GUITAR FUZZ
A classic design based around an op-amp - NOT TESTED

BASS/TREBLE TONE CONTROL
A neat little circuit providing +/- 3dB bass and treble boost

BASS/TREBLE TONE CONTROL - OP AMP VERSION
Another bass and treble boost tone control giving better performance using a single op-amp

BASS BOOSTER
A simple active op-amp filter that will boost and cut bass signals - possibly as part of a sub-woofer

FILTER - ACTIVE LOW PASS
Active filter based on Sallen Key design. Ideal for tone controls, subwoofer drivers and demodulating

FILTER - ACTIVE HIGH PASS
Active filter Sallen Key design. Ideal for tone controls, tweeter/midrange drivers and demodulating

PARAMETRIC EQUALISER
Tailor your audio with this variable frequency cut/boost filter

RING MODULATOR
Useful for sound effects - simple in design, based on just 2 transformers and 4 diodes - NOT TESTED

SOUND ACTIVATED SWITCH
This was connected to a battery powered mobile which activated when a baby cried

THEREMIN- NEW
Asimple version of a more complex design - enables you to literally play tune by hand!!

TRIANGLE WAVE AUDIO ASTABLE
A useful replacement for a sine wave generator, has AC/DC output and square and triangle outputs

VCA - VOLTAGE CONTROLLED AMPLIFIER
Fantastic little circuit that can be configured as a VCA, modulator and multiplier.

LOTTERY NUMBER GENERATOR
Good for generating those lottery numbers!

36 LED Chaser
A multiplexed display to produce a chaser - LED's were mounted in a circle - - -

4 Way Spinner
A 4 light bulb spinner that slows and stops on a random bulb. - - -

DIGITAL DICE AND DOUBLE DIGITAL DICE
A electronic dice with LED display that powers down after 30 seconds

HEADS OR TAILS COIN TOSS - UPDATED
A simple hand held Heads or tails decision maker.

Roulette wheel v2
A light sequencer with a few extra features. - - -

Steady Hand Game
A controller to use with a steady hand game - gives you up to 10 chances - -

Survival Game
Jump up the ladder withiout falling off, a game of skill - used in GCSE project - -

10 CHANNEL LIGHT CONTROLLER
A 10 channel light controller using PWM/ Up to 1A per channel at 12v

BATTERY CHARGER - Constant Current
A constant current fast charger for high current applications, RC etc. - -

BATTERY CONDITIONER
Keeps unused lead-acid batteries fit and healthy when not in use - uses binary counters

Bite Alarm - Pulsed Tone Generator
Produces a pulsed tone with adjustable speed, duration, pitch and volume. - - -

CAR IMOBILISER
A switch operated by keypad and PIN. Can be used as a Car Imobiliser or simple combination switch

COMBINATION LOCK
A digital lock with keypad - enter the correct code to operate a solenoid. Based around UA3730

COMBINATION LOCK2
A digital lock with switches. A nifty circuit I'm chuffed with, based around just 2 logic ICs!

DIRECTIONAL SPEED CONTROLLER
Based on the RC Speed Controller - with the addition of an astable, you get a stand alone controller.

DRILL SPEED CONTROLLER V2
PWM controller derived from a ramp generator and comparator - also drives lamps and other devices

Fridge Alarm - version 1
Activated by the light in a fridge. Sounds an alarm if the door is left open too long - -

Fridge Alarm - version 2
Same as before but produces a pulsed alarm tone - -

FULL BRIDGE MOSFET MOTOR DRIVER
This 10A MOSFET driver will power most small to medium power DC motors up to 24v

Full Bridge Transistor Motor Driver
Ideal for PWM/Robotics / Radio Control - -

Intelligent Lithium/NiMH battery charger
A nifty little circuit that monitors the battery voltage as it gets charged - -

MOTORBIKE BATTERY CHARGER - NEW
This will top-up your motorbike battery in 2-3 hours and switch off

Race Starter Controller
Ideal to enhance any Scalectrix race track. - - -

RC SPEED CONTROLLER
Fed up of paying £20 for controllers? Try this 10Amp PIC version with a calibration feature.

Tank Heater
A PWM power controller used to control the temperature in a tank for a tarantula - - -

1-90 Bingo Number Generator
A neat little counter counting from 1 to 90 (not zero) with the aid of a few gates - -

24 Hour Clock 2
An example of using gates to "trap" binary values on counters - -

24 HOUR TIMER
A timer that will switch on for 12/24 hours, once or repeat, can be modified for up to 2 weeks!

Boxing Timer
A student needed a timer that counted down one minute. This does exactly that - -

Digital Stopwatch
Times up to an hour in tenths of a second - -

DUAL 7-SEGMENT SCOREBOARD
A dual display that has controls to count up, down and reset. Runs from 5-12volts - -

Door Monitor
Counts the number of times a door is opened. Single digit but can be easily expanded - -

EGG TIMER
Two 555 timers, sound at the end of the time period, one beeps, the other bleeps! -

FISH FEEDER
An interval timer that can pulse a feeder on for 10-22 seconds every 1,2 or 4 hours

Large 7-segment Display board
A resizeable display from 40mm to 150mm! - -

Room Sentry
Counts the number of people entering a room, for use with a PIR module - -

Scalectrix Lap Timer
Works by using an LDR under the track, times alternate laps in 10ths of a second - -

Single Digit Scoreboard
A compact general purpose display. - -

VERSATILE TIMER IC
An 8-pin PIC generating hourly/daily pulses, saves lots of circuitry - example circuits also

1.5v Battery meter
Simple but effective way of testing 1.5 volt cells - -

12 Volt Car Battery Meter
A 10 LED calibrated voltmeter from 11-15 volts, needs no extra battery - -

Audio VU Meter
A VU meter with 20 LED's. The input source can be a line input or a microphone - -

FREQUENCY TO VOLTAGE CONVERSION
Using the LM2917 for a few useful applications -

LED Battery Meter
Will measure any low voltage battery on a 10 LED scale! - -

LED Strobe
With high power LED's available, their replacement for a Xenon tube is viable! - -

LED STROBE 2 - NEW
This version has been built and tested and is very simple indeed - based on Alien project astable!

REV COUNTER
A 10-LED Rev Counter/Tachometer using the LM2917. Also a general purpose frequency-voltage circuit

SERVO TESTER - NEW
A simple circuit based around one logic IC which will test/control most radio-control type servos

TRIANGLE WAVE AUDIO ASTABLE - NEW
A useful replacement for a sine wave generator, has AC/DC output and square and triangle outputs

12v LIGHT DIMMER v2
This version controls lights, LEDs and even motors with only 10 components - up to 50W!

AUTOMATIC BILGE PUMP SENSOR - NEW
This simple circuit will keep your engine bay under control and draws no current while in standby

Dog Warden
A simple radio transmitter and reciever to signal when a dog has strayed too far - -

INVERTER
Generates a negative supply in a battery circuit for split power supply circuits.

KEYPAD DECODER - NEW
Decodes and generates a standard 4x3 keypad to produce a 4-bit binary output.

Night Rider 2
This version has been built and tested - includes drive circuitry and PCB

Knight Rider
An adaption of the Light Bouncer makes a classic light chaser - -

Light Bouncer
A a simple chaser from a decade counter - bounces a light on 6 bulbs - -

Remote Control Beeper
Uses RF Tx/Rx modules with a range of about 30m. - -