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4QD-TEC: Electronics Circuits Reference Archive

Introduction

Hello and welcome to 4QDtec.com This site contains a wide range of circuits and general electronic design information created by the founder of 4QD. It started life as a subscription club, but has now evolved into a free access site. It was written a while ago without the style tools that available now, so apologies for the way it looks, but hopefully you'll find the content useful. A lot of the circuits are designed using discrete components rather than ICs, this was the author's personal preference and can provide a solid, old school grounding in fundamental electronic design principles.

Copyright

4QD Ltd manufacture electronic motor speed controls for battery motors. We don't publish our latest and commercially sensitive circuits. However a lot of the ones here are original and although you are free to use them for your own entertainment, 4QD Ltd retains intellectual property rights to them insofar as they may have commercial value. If you do find them commercially useful, then please contact us for permission to use them. Under no circumstances may they be published in any form without written permission from the author.

Disclaimer

These circuits are supplied 'as is' at no charge, for your enjoyment. So far as we are aware they are complete and work but we can take no responsibility for any errors. Most, but not all, of the circuits are our own design. As far as we are aware no copyright other that the author's exists on any of them but we cannot guarantee this.

Site Index

The list below is not as long as it looks because it sometimes contains many entries to the same circuit. If so, this is because the circuit has many uses or can be called different things.

The index is one long list of all available circuits in alphabetical order. It is however divided into the following areas:

Index Contents

Audio Circuits

Automobile Circuits

Battery Monitoring circuits

Beginner's articles

Circuit Theory and tutorials

Component types and values

Components

Computing

Current sensing and control

Guitar Effects Circuits

LED Control circuits

Industrial Control circuits and suggestions

Measurement Circuits

Motor Control Circuits

Multivibrators

Oscillator Circuits

Power Supply circuits

Pulse (Width and position) Modulation Circuits

Relay Driver Circuits

Staircase generators

Switch Circuits

Test Equipment circuits

Temperature Measurement

Timer Circuits

Ultrasonic Circuits

Voltage/Current controlled circuits

Alphabetical Index

Analogue circuits, Various (Download zip file)

Analogue 'counter'

Analogue difference detector

Analogue isolator

Astable Multivibrators

Audio Circuits

Amplifier, very low THD

Sinclair circuits and other Sinclair info

Graphic Equaliser

Preamplifiers

LED VU meter

LED VU meter

Peak program indicator, speaker powered

Various Audio circuits (Download zip file)

Automobile Circuits

Various Auto circuits

Automotive Trafficator Circuit

Tacho and Dwell Meter

Battery Monitoring circuits

Battery Condition Meters the circuits of 4QD's own BCM.

Battery discharger

Battery low indicator

Various Battery circuits

Beginner's articles - A selection of articles written for those new to electronics

Electricity - an analogy with water

How pwm works

Bistable Latch

Bridge, Full. For motor control

Bridge, Full. Switching of

Bridge, Half. For motor control

Bridge, Half. Current and voltage commutation waveforms

Charge pump. Cup and bucket

Circuit Theory and tutorials

Colour codes and multipliers for resistors and capacitors

Current sources and mirrors

Electricity - an analogy with water (good start for beginners)

Emitter Coupled Multivibrators

Filter Circuits (Download zip file) Single transistor Gyrator, Multi-feedback, Twin T

Logic circuits using discretes

Mice How your computer mouse works

Op-amp circuits using discrete transistors

Two transistor regulator circuits

Various Circuit Configurations (Download zip file)

Components

Reed switches How to use them

Component types and values

Colour codes and multipliers for resistors and capacitors

Testing MOSFETs

Comparator with controlled hysteresis

Component values and colour code

Converter circuits (Download zip file) D to A, V to Time

Cup and bucket charge pump

Computing

Possible bug in Wireless Router adaptive learning?

Current sensing and control

Current Controlled Amplifier

Current loop interface

Current Monitoring Circuits

Current sensing relay driver

Current sources and mirrors a 'lecture'

Current source, Switching

Data switch and indicator, bi-directional

Discrete transistor Circuits (Download zip file) Op Amps, Logic

Driver Circuits Totempole drivers

Domestic heating control circuit

Electric Field detector

Electricity - an analogy with water (good start for beginners)

Follower Circuits

Full bridge for motor control

Game circuits

Graphic Equaliser

Guitar Effects Circuits

Phaser

Gyrator - used in graphic equaliser

H Bridge Switch. For small motors

Hall effect Current sensing

'Jeopardy' circuit

Industrial Control circuits and suggestions

Analogue 'counter'

Analogue isolator

Bistable Latch

Coil catching diodes AKA flywheel diodes. Why they are needed.

Current loop interface

Current sensing relay driver

H Bridge Switch. For small motors

Industrial process control circuits

Impulse relay circuit Pulse to set, pulse to reset

Modular industrial relay system Base relay allows timers etc to be added

Opto isolator, Analogue

Relay driver, transistorised

Stepper motor, clock oscillator

Switch, Impulse changeover

Switching Solenoid Driver

Timer circuits

Impulse changeover Switch

Industrial process control circuits

Intercom with speaker as microphone

Joystick Interfaces

Lab Power supply (Download zip file) 0-50 volts, 0-5 amps or whatever you decide.

Lamp and Bulb drivers

Latch, Data bi-directional

Leakage detector

LED Control circuits

LED Driver Circuits

LED Volt Meters 4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions

LED VU meter

LED brightness control circuits

Logic circuits using discretes

Logic Circuits (Download zip file) Latches. Transparent data, R-S etc.

Mains Wiring detector

Mathematical Analyses (Download zip file) One TUN gyrator

Mice How your computer mouse works

Microphone preamplifiers

Modulators, Pulse Width

MOSFET current sensing

MOSFET testing

Measurement Circuits

Hall effect Current sensing

LED Volt Meters 4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions

LED VU meter

Testing MOSFETs Use a multimeter to test a MOSFET

Peak Detecting Circuits

Voltage breakdown tester (Download zip file) for transistors and diodes etc

Motor Control Circuits

Analogue isolator

Battery Current Limiting

Bridge, Full. For motor control

Part 1: Bridge, Half. For motor control A discussion

Part 2: PWM motor speed control Deals with early 2QD circuits

Part 3: PWM motor speed control Development of 2QD series

Part 4: PWM motor speed control Modern 2QD series. Detailed discussion

Part 5: PWM motor speed control Ramping and reversing. NCC series controllers

Part 6: PWM motor speed control Waveforms and commutation in a MOSFET half bridge

Part 7: PWM motor speed control MOSFET full bridge switching using two half bridges

Part 8: PWM motor speed control MOSFET full bridge switching - Fully complementary

PWM motor speed control Part 7 Starts to deal with Full bridge control

Constant Power throttle How do simply incorporate constant power throttle

H Bridge Switch. For small motors

MOSFET current sensing

Pulse Width modulators

Pulse Width modulators Several circuits

PWM motor control Many more articles, including constructional information and theory.

Tacho generator amplifier As used in 4QD's Tacho feedback board

Multipliers (3n3 etc) for resistors and capacitors

Multivibrators

Multivibrators

Multivibrator, emitter coupled Linear ramps, good waveform

Test ramp generator, for power device testing A practical application of the emitter coupled multivibrator Multivibrator circuits(Download zip file) Astables. Bistables, Ring Astables

Op-amp circuits using discrete transistors

Opto isolator, Analogue

Oscillator Circuits

Multivibrator, emitter coupled Linear ramps, good waveform

Quadrature (sine/cosine) voltage controlled, quasi-sinusoids

Three phase

Voltage controlled programmable, wide range.

Relaxation oscillators multivibrators

Wien Bridge

Oscillators(Download zip file) Multivibs, Ramp generators, Sawtooth,
Sinewave, Sounders, VCOs, Waveform Generators

Peak Detecting Circuits

Person detector

Phaser for audio/guitar effects

Power Supply circuits

Power supplies with enable and automatic switchoff

Power supply tripped, regulated, high current

Power supply Re-entrant, regulated, high Current

Power supply, Lab type(Download zip file) 0-50 volts, 0-5 amps or whatever you decide.

Power Supply Circuits Various

Two transistor regulator circuitsa theoretical discussion

Preamplifiers, audio

Preamplifiers, ultrasonic

Programmable Unijunction Transistor

Precision rectifier circuit in tacho amplifier

Precision rectifier circuit in Joystick interface

Pulse (Width and position) Modulation Circuits

Pulse Width modulators

Pulse Width Modulators

Pulse Width Position Servo control

PWM motor control - part one of a serieslinks to much more in member's area

2QD controller Circuit diagram, component list, PCB layout

Pulse Processing Circuits

Pulse width comparator

Pulse width to voltage converter

Pump and hold (staircase)

PUT pair 2 Tr equivalent to SCRs, SCSs and other 4 layer devices

PWM motor control

Quadrature (sine/cosine) oscillator voltage controlled

Radio Control Interface

Ramp generator (separate + & - ramps)

Ramp Circuits Ramping and Slew Rate control

Relaxation oscillators

Relay Driver Circuits

Impulse relay circuit Pulse to set, pulse to reset

Latching, transistorised

Relay driver, transistorised

Relay logic: Start/Stop buttons

Switching Solenoid Driver

Drive two relays via one wire

Relay Driver Circuits

Resistor colour code

Rotary Encoder Circuits

Robot wars: start here!

Schmitt Trigger: an unusual circuit

Sinewave Generator

Staircase generators

Staircase generator

Staircase generator

Staircase Generators

Stepper motor used as encoder

Stepper motor, clock oscillator

Switch Circuits

Toggle action switches(Download zip file)

Data Switches(Download zip file)

Touch operated Switches(Download zip file)

Switch, Impulse changeover

Switch, Touch operated

Switching Solenoid Driver

Tacho generator feedback circuit

Test Equipment circuits

Lab Power supply 0-50 volts, 0-5 amps or whatever you decide.

Voltage breakdown tester for transistors and diodes etc

Test Ramp generator For Power device curve tracing

Semiconductor Testers JFET offset voltage tester, Diode Vf tester
Beta Meter, Bipolar polarity checker

Temperature Measurement

Thermometer and thermostat for Room temperatures

Thermostat

Thermostat circuits

Timer Circuits

Timer: delay on de-energise

Timer: delay on energise

Timer: pulse output

Touch operated Switches

Twin-T oscillator

Twin-T tuned Ultrasonic Preamp

Ultrasonic Circuits

Ultrasonic Intruder detector

Ultrasonic Preamp with AGC

Ultrasonic Preamp with Twin-T tuning

Ultrasonic Receiver

Ultrasonic Transmitter

Understanding Electricity - an analogy with water

LED Volt Meters 4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions

Voltage breakdown tester(Download zip file) for transistors

Voltage breakdown tester circuits

Voltage/Current controlled circuits

Current Controlled Amplifier

Oscillator, Quadrature (sine/cosine)

Oscillator - multivibrator type

Oscillator, programmable, wide range

Voltage and Current controlled amps

VU LED meter

Waveform generator circuits

Wien Bridge oscillator

Window Detectors


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© 1997-2019 4QD-TEC
First published:
Page's Author: Richard Torrens