4QD-TEC Circuits Archive

Index for this page.

This page contains the main index to the electronics section of this site, with certain other general information which you may need.

• Site Index of electronic circuits.

• 4QD TEC
• Introduction
• To Join 4QD-TEC use the button at head or foot of any free page.
• Members private data area if you have a password.
• Transistors or ICs?
• Transistor types
• Educational Resource
• Problems and queries
• Future Plans
• Copyright
• Disclaimer

This site, large though it is, is only the public 'front end' of a subscription electronics club - 4QD-TEC.

For more information and how to join, use the 'Join' button at head or foot of any free page.

Introduction

You will need images on for this area of the site - to see the circuit diagrams (PNG or GIF).

As these pages of circuits (a lot more at the bottom of this one) are proving to be of interest to browsers we are gradually expanding them to give a larger selection of interesting and, perhaps, useful circuits as well as a lot of various information. We want to make our site interesting and useful - not pretty and impressive. Hopefully some of you, one day, may need a PWM motor controller and will remember us!

I know a lot of visitors are coming straight to this index rather than to our Home page. You are welcome - but there are pointers on the home page to other info which is not circuit diagrams. There will be links to other sites, info on manufacturers and suppliers of goods related to our business as well as information on computing and electronics and maybe other subjects. Who knows what else! The author has written for computer magazines, DIY magazines and others.

4QD sell motor controllers: we do not sell web technology. Therefore you won't find animated GIFs, Java Applets or advice to use one particular browser: our pages should work with any browser that can display GIFs and JPEGs. There will be added, in time, one or two JavaScript calculators however.

Transistors or ICs?

Educational Resource

All of which the above makes this site a very good educational resource, and it is evident from the comments we get that it is being used as such. So we intend to expand this area - partially in an attempt to make the site commercially viable. We intend therefore to make circuit board designs available for some of the projects and educational establishments that require reasonable quantities (25 or more) are welcome to contact 4QD to discuss their requirements. We will be able to supply circuit boards for some of the interesting circuits, with kits of parts and assembly information. We can clearly link the boards and kits to constructional information on this site, or we can supply printed out information.

I have however tried to make this site easy to read, so the descriptions aren't too simple or full of maths. Maybe you want this altered - let me know.

Problems and queries.

Future Plans

The public area of 4QD-TEC is large: future expansion will be in the private area, which is only available to members. This data includes much on PWM motor control (as you might expect) but also lots of other information, including more detailed circuit descriptions and constructional information.

Copyright

4QD manufacture electronic motor speed controls for battery motors. We make our living by selling some of our circuits. Obviously I'm not going to publish commercially sensitive circuits! However a lot of the ones I publish are original and although you are free to use them for your own entertainment, the author retains intellectual property rights to them insofar as they may have commercial value. If you do find them commercially useful, then please contact me 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. We will of course offer any reasonable assistance if you do hit problems. 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 (besides - it makes the list longer!)

Key: Left hand Column

Some of these items are public. Some are members only. Some have a public 'front' but more is available to members. So the left hand column is a key to what is what.

MO	Information is Members Only. You will be asked for a pasword.
ML	Information is Members Only. These are 'Library' collections of circuits with no write-up. You will be asked for a pasword.
PA	Public area information.
PM	Public area information, with more information available to members.

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

Index Contents

Alphabetical Index

ML	Analogue circuits, Various
PA	Analogue 'counter'
PA	Analogue isolator
PA	Astable Multivibrators
Audio Circuits
PA		Amplifier, very low THD
MO		Sinclair circuits and other Sinclair info
PA		Graphic Equaliser
PA		Preamplifiers
PA		LED VU meter
PA		Signal Generator
ML		Various Audio circuits
Automobile Circuits
ML		Various Auto circuits
PA		Automotive Trafficator Circuit
PA		Tacho and Dwell Meter
Battery Monitoring circuits
MO		Battery Condition Meters	the circuits of 4QD's own BCM.
PA		Battery discharger
PA		Battery low indicator
ML		Various Battery circuits
Beginner's articles			A selection of articles written for those new to electronics
PA		Electricity - an analogy with water
PA		How pwm works
MA	Bistable Latch
PA	Bridge, Full. For motor control
MO	Bridge, Full. Switching of
SM	Bridge, Half. For motor control
MO	Bridge, Half.		Current and voltage commutation waveforms
PA	Charge pump. Cup and bucket
Circuit Theory and tutorials
PA		Colour codes and multipliers	for resistors and capacitors
PA		Current sources and mirrors
PA		Electricity - an analogy with water	(good start for beginners)
MO		Emitter Coupled Multivibrators
ML		Filter Circuits	Single transistor Gyrator, Multi-feedback, Twin T
PA		Logic circuits using discretes
PA		Mice	How your computer mouse works
PA		Op-amp circuits	using discrete transistors
PA		Two transistor regulator circuits
ML		Various Circuit Configurations
Components
PA		Reed switches	How to use them
Component types and values
PA		Colour codes and multipliers	for resistors and capacitors
PA		Testing MOSFETs
PA	Comparator with controlled hysteresis
PA	Component values and colour code
ML	Converter circuits		D to A, V to Time
PA	Cup and bucket charge pump
Computing
PA		Possible bug in Wireless Router adaptive learning?
Current sensing and control
PA		Current Controlled Amplifier
PA		Current loop interface
ML		Current Monitoring Circuits
PA		Current sensing relay driver
PA		Current sources and mirrors	a 'lecture'
PA		Current source, Switching
PA	Data switch and indicator, bi-directional
ML	Discrete transistor Circuits		Op Amps, Logic
ML	Driver Circuits		Totempole drivers
PA	Domestic heating control circuit
PA	Electric Field detector
PA	Electricity - an analogy with water		(good start for beginners)
ML	Follower Circuits
PA	Full bridge for motor control
PA	Game circuits
PA	Graphic Equaliser
Guitar Effects Circuits
PA		Phaser
PA	Gyrator - used in graphic equaliser
PA	H Bridge Switch. For small motors
PM	Hall effect Current sensing
PA	'Jeopardy' circuit
Industrial Control circuits and suggestions
PA		Analogue 'counter'
PA		Analogue isolator
PM		Bistable Latch
PA		Coil catching diodes	AKA flywheel diodes. Why they are needed.
PA		Current loop interface
PA		Current sensing relay driver
PA		H Bridge Switch. For small motors
PM		Industrial process control circuits
PA		Impulse relay circuit	Pulse to set, pulse to reset
PM		Modular industrial relay system	Base relay allows timers etc to be added
PA		Opto isolator, Analogue
PM		Relay driver, transistorised
PA		Stepper motor, clock oscillator
PA		Switch, Impulse changeover
PA		Switching Solenoid Driver
PM		Timer circuits
PA	Impulse changeover Switch
PM	Industrial process control circuits
PA	Intercom with speaker as microphone
PA	Joystick Interfaces
MO	Lab Power supply		0-50 volts, 0-5 amps or whatever you decide.
ML	Lamp and Bulb drivers
PA	Latch, Data bi-directional
PA	Leakage detector
LED Control circuits
ML		LED Driver Circuits
MO		LED Volt Meters	4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions
PA		LED VU meter
PA		LED brightness control circuits
PA	Logic circuits using discretes
ML	Logic Circuits		Latches. Transparent data, R-S etc.
PA	Mains Wiring detector
ML	Mathematical Analyses		One TUN gyrator
PA	Mice		How your computer mouse works
PA	Microphone preamplifiers
PA	Modulators, Pulse Width
PM	MOSFET current sensing
PA	MOSFET testing
Measurement Circuits
PM		Hall effect Current sensing
MO		LED Volt Meters	4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions
PA		LED VU meter
PA		Testing MOSFETs	Use a multimeter to test a MOSFET
ML		Peak Detecting Circuits
MO		Voltage breakdown tester	for transistors and diodes etc
Motor Control Circuits
PA		Analogue isolator
PM		Battery Current Limiting
PA		Bridge, Full. For motor control
PA	Part 1	Bridge, Half. For motor control	A discussion
MO	Part 2	PWM motor speed control	Deals with early 2QD circuits
MO	Part 3	PWM motor speed control	Development of 2QD series
MO	Part 4	PWM motor speed control	Modern 2QD series. Detailed discussion
MO	Part 5	PWM motor speed control	Ramping and reversing. NCC series controllers
MO	Part 6	PWM motor speed control	Waveforms and commutation in a MOSFET half bridge
MO	Part 7	PWM motor speed control	MOSFET full bridge switching using two half bridges
MO	Part 8	PWM motor speed control	MOSFET full bridge switching - Fully complementary
MO		PWM motor speed control Part 7	Starts to deal with Full bridge control
PM		Constant Power throttle	How do simply incorporate constant power throttle
PA		H Bridge Switch.	For small motors
PM		MOSFET current sensing
PA		Pulse Width modulators
ML		Pulse Width modulators	Several circuits
PM		A new PW Modulator	double triangle waveforms, independently adjutable slopes
PM		PWM motor control	Many more articles, including constructional information and theory.
PA		Tacho generator amplifier	As used in 4QD's Tacho feedback board
PA	Multipliers		(3n3 etc) for resistors and capacitors
Multivibrators
PA		Multivibrators
MO		Multivibrator, emitter coupled	Linear ramps, good waveform
MO		Test ramp generator, for power device testing	A practical application of the emitter coupled multivibrator
ML		Multivibrator circuits	Astables. Bistables, Ring Astables
PA	Op-amp circuits using discrete transistors
PA	Opto isolator, Analogue
Oscillator Circuits
MO		Multivibrator, emitter coupled	Linear ramps, good waveform
PA		Quadrature (sine/cosine)	voltage controlled, quasi-sinusoids
PA		Three phase
PA		Voltage controlled	programmable, wide range.
PA		Relaxation oscillators	multivibrators
PA		Wien Bridge
ML		Oscillators	Multivibs, Ramp generators, Sawtooth, Sinewave, Sounders, VCOs, Waveform Generators
ML	Peak Detecting Circuits
PA	Person detector
PA	Phaser for audio/guitar effects
Power Supply circuits
PM		Power supplies with enable	and automatic switchoff
PA		Power supply	tripped, regulated, high current
MO		Power supply	Re-entrant, regulated, high Current
MO		Power supply, Lab type	0-50 volts, 0-5 amps or whatever you decide.
ML		Power Supply Circuits	Various
PA		Two transistor regulator circuits	a theoretical discussion
PA	Preamplifiers, audio
PA	Preamplifiers, ultrasonic
PA	Programmable Unijunction Transistor
PA	Precision rectifier circuit		in tacho amplifier
PA	Precision rectifier circuit		in Joystick interface
Pulse (Width and position) Modulation Circuits
PA		Pulse Width modulators
ML		Pulse Width Modulators
PA		Pulse Width Position Servo control
PA		PWM motor control - part one of a series	links to much more in member's area
MO		2QD controller	Circuit diagram, component list, PCB layout
ML	Pulse Processing Circuits
PA	Pulse width comparator
PA	Pulse width to voltage converter
PA	Pump and hold (staircase)
PA	PUT pair		2 Tr equivalent to SCRs, SCSs and other 4 layer devices
PA	PWM motor control
PA	Quadrature (sine/cosine) oscillator		voltage controlled
PA	Radio Control Interface
PA	Ramp generator		(separate + & - ramps)
ML	Ramp Circuits		Ramping and Slew Rate control
PA	Relaxation oscillators
Relay Driver Circuits
PA		Impulse relay circuit	Pulse to set, pulse to reset
PM		Latching, transistorised
PM		Relay driver, transistorised
PA		Switching Solenoid Driver
ML		Relay Driver Circuits
PA	Resistor colour code
ML	Rotary Encoder Circuits
PA	Robot wars: start here!
PA	Schmitt Trigger: an unusual circuit
PA	Sinewave Generator
Staircase generators
PA		Staircase generator
PA		Staircase generator
ML		Staircase Generators
PA	Stepper motor used as encoder
PA	Stepper motor, clock oscillator
Switch Circuits
ML		Toggle action switches
ML		Data Switches
ML		Touch operated Switches
PA		Switch, Impulse changeover
PA		Switch, Touch operated
PA	Switching Solenoid Driver
PA	Tacho generator feedback circuit
Test Equipment circuits
MO		Lab Power supply	0-50 volts, 0-5 amps or whatever you decide.
MO		Voltage breakdown tester	for transistors and diodes etc
MO		Test Ramp generator	For Power device curve tracing
ML		Semiconductor Testers	JFET offset voltage tester, Diode Vf tester Beta Meter, Bipolar polarity checker
Temperature Measurement
PA		Thermometer and thermostat	for Room temperatures
PA		Thermostat
ML		Thermostat circuits
Timer Circuits
PM		Timer: delay on de-energise
PM		Timer: delay on energise
PM		Timer: pulse output
PA	Touch operated Switches
PA	Twin-T oscillator
PA	Twin-T tuned Ultrasonic Preamp
Ultrasonic Circuits
PA		Ultrasonic Intruder detector
PA		Ultrasonic Preamp with AGC
PA		Ultrasonic Preamp with Twin-T tuning
PA		Ultrasonic Receiver
PA		Ultrasonic Transmitter
PA	Understanding Electricity - an analogy with water
MO	LED Volt Meters		4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions
MO	Voltage breakdown tester for transistors
MO	Voltage breakdown tester circuits
Voltage/Current controlled circuits
PA		Current Controlled Amplifier
PA		Oscillator, Quadrature (sine/cosine)
PA		Oscillator - multivibrator type
PA		Oscillator, programmable, wide range
ML		Voltage and Current controlled amps
PA	VU LED meter
PA	Waveform generator circuits
PA	Wien Bridge oscillator
ML	Window Detectors

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