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4QD-TEC: Electronics Circuits Reference ArchiveIntroductionHello 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. Copyright4QD 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. DisclaimerThese 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 IndexThe 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 ContentsIndustrial Control circuits and suggestions Pulse (Width and position) Modulation Circuits Voltage/Current controlled circuits Alphabetical IndexAnalogue circuits, Various (Download zip file) Audio Circuits
Sinclair circuits and other Sinclair info Peak program indicator, speaker powered Various Audio circuits (Download zip file) Automobile Circuits
Automotive Trafficator Circuit Battery Monitoring circuits
Battery Condition Meters the circuits of 4QD's own BCM. Beginner's articles - A selection of articles written for those new to electronics
Electricity - an analogy with water Bridge, Full. For motor control Bridge, Half. For motor control Bridge, Half. Current and voltage commutation waveforms Circuit Theory and tutorials
Colour codes and multipliers for resistors and capacitors 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 Comparator with controlled hysteresis Component values and colour code Converter circuits (Download zip file) D to A, V to Time Computing
Possible bug in Wireless Router adaptive learning? Current sensing and control
Current sources and mirrors a 'lecture' Data switch and indicator, bi-directional Discrete transistor Circuits (Download zip file) Op Amps, Logic Driver Circuits Totempole drivers Domestic heating control circuit Electricity - an analogy with water (good start for beginners) Guitar Effects Circuits
Gyrator - used in graphic equaliser H Bridge Switch. For small motors Industrial Control circuits and suggestions
Coil catching diodes AKA flywheel diodes. Why they are needed. 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 Stepper motor, clock oscillator Industrial process control circuits Intercom with speaker as microphone Lab Power supply (Download zip file) 0-50 volts, 0-5 amps or whatever you decide. LED Control circuits
LED Volt Meters 4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions LED brightness control circuits Logic circuits using discretes Logic Circuits (Download zip file) Latches. Transparent data, R-S etc. Mathematical Analyses (Download zip file) One TUN gyrator Mice How your computer mouse works Measurement Circuits
LED Volt Meters 4QD's 3, 5 and 7 LED voltmeters, circuits, partslist, descriptions Testing MOSFETs Use a multimeter to test a MOSFET Voltage breakdown tester (Download zip file) for transistors and diodes etcMotor Control Circuits
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 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
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 Oscillator Circuits
Multivibrator, emitter coupled Linear ramps, good waveform Quadrature (sine/cosine) voltage controlled, quasi-sinusoids Voltage controlled programmable, wide range. Relaxation oscillators multivibrators Oscillators(Download zip file) Multivibs, Ramp generators, Sawtooth,Sinewave, Sounders, VCOs, Waveform Generators 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 Programmable Unijunction Transistor Precision rectifier circuit in tacho amplifier Precision rectifier circuit in Joystick interface Pulse (Width and position) Modulation Circuits
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 width to voltage converter PUT pair 2 Tr equivalent to SCRs, SCSs and other 4 layer devices Quadrature (sine/cosine) oscillator voltage controlled Ramp generator (separate + & - ramps) Ramp Circuits Ramping and Slew Rate control Relay Driver Circuits
Impulse relay circuit Pulse to set, pulse to reset Relay logic: Start/Stop buttons Schmitt Trigger: an unusual circuit Staircase generators
Stepper motor, clock oscillator Switch CircuitsToggle action switches(Download zip file) Data Switches(Download zip file) Touch operated Switches(Download zip file)Tacho generator feedback circuit Test Equipment circuitsLab Power supply 0-50 volts, 0-5 amps or whatever you decide. Voltage breakdown tester for transistors and diodes etcTest Ramp generator For Power device curve tracing Semiconductor Testers JFET offset voltage tester, Diode Vf tester Temperature Measurement
Thermometer and thermostat for Room temperatures Timer Circuits
Twin-T tuned Ultrasonic Preamp Ultrasonic Circuits
Ultrasonic Preamp with Twin-T tuning 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 transistorsVoltage breakdown tester circuits Voltage/Current controlled circuits
Oscillator, Quadrature (sine/cosine) Oscillator - multivibrator type Oscillator, programmable, wide range Voltage and Current controlled amps
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