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Control Circuits

 
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Last Updated: October 24, 2017 02:54 PM

Circuits Designed by Dave Johnson, P.E.

Thermostat for 12v Cooling FanThis circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2011

Three Volt Universal LED FlasherThe circuit below will flash any LED color with fixed current pulses powered by a 3v battery.  It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement.  Using this approach, white and . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2008

Three-Minute Closet LightI have a coat closet by my front door.  The thing is very dark at night and really needs some kind of illumination inside.  I could hire an electrician to install a light in the closet ceiling and then wire it to a toggle switch outside the door but that would cost me quite a bit of money. . . Circuit by David A. Johnson P.E.-December, 2011

Three-Volt Low Battery Voltage FlasherMany battery powered devices use two AA alkaline cells.  Often you will not know when it is time to replace the batteries until the device powered by them actually stops operating.  The hobby circuit below can be connected to a 3v battery, to give you some . . . Hobby Circuit designed by David Johnson P.E.-January, 1998

Three-Volt Powered Super Bright LED FlasherI have posted several kinds of LED flashers over the years.   This is yet one more flasher, designed to flash any high power LED of any color.  It hits the LED with a 25ms 250ma pulse once every 2 seconds.   This works out to an average current about 3ma.  It . . . Hobby Circuit designed by David Johnson P.E.-April, 2009


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

The Curious Incident of the Dog in the Night -  26-Sep-05 -Design News:   Sometimes you can't teach an old dog new tricks.  Tired of trudging down the stairs to let his dog out of his cage in the middle of the night, Les designed a remote control door opener.  The system consists of a clevis mounted to the shaft of a solenoid and the door latch of the cage.  When Les __ Gadget Freak

The dual slope-sampling solar engine -  If you had time to experiment with the ALF type SE circuit you may have discovered some of its shortcomings with regard to a Power Smart Head adaptation.  __ Designed by Wilf Rigter

The GBSE (gate boost solar engine) -  The Gate Boost SE uses a 1381, a 2N7000 MOSFET and a 2N3906 with a unique voltage doubler to increase the voltage applied to the gate of the MOSFET.  Normally the 2.6V output of a 1381C is barely able to turn on the 2N7000.  As a result the "on resistance" of the MOSFET is high and much power is wasted.   __ Designed by Wilf Rigter

The HC11 Controls the Stepper -  Simple circuit with 16-pin Nitron chip 68HC908, easy analog setting, source code with ICC08.  New s-record for 8-pin 68HC908QT2! __ Designed by Ludwig Orgler-Fachingenieur Elektrotechnik

The Inexpensive Dimmable LED Desk Lamp -  30-Nov-12 -Design News:   Andrew Morris designed a dimmable LED driver circuit that is simple and energy efficient.  He then installed the circuit into a portable fluorescent lamp. __ Designed by Andrew R. Morris, Gadget Freak-Case #230

The LED Flasher -  This is a very simple project using a printed circuit board and 8 components.  It will flash an ordinary 3mm or 5mm (1/8" or 1/4") LED at a rate of about one flash per second.   __ Designed by Collin Mitchell

The LED Flashing Sweetheart Kit -  When was the last time you gave a gift you made yourself? Elementary school? Get off the consumerist fast track and quit copping out with inferior gifts like candy and flowers.  The LED Flashing Sweetheart Kit contains a circuit board, 28 LEDs

The Lights Are On, but No One's Home -  Find out how you can control your environment. __ Contact: Jameco Electronics

The MicroPower Solar Engine -  A 'micro power solar engine' has been a goal since my introduction to BEAM Robotics.  I believe that if there wasn't one before, I there is one now.  What I'm presenting to you looks very similar to one of the circuits found in Steven Bolt's web pages.  As you will see, I made only minor changes to that design and not without help.   __ Designed by Ken Huntington

The Miller solar engine -  The Miller solar engine uses a 1381* voltage detector (a.  k.  a.  , a voltage supervisor) IC to drive a voltage-based (type 1) solar engine.  The 1381 is normally used to reset CPUs and Micros when the power supply drops too low for reliable operation.  So 1381s detect and switch when the input voltage crosses the rated upper and lower threshold voltages.  The upper- and lower-switching voltages are slightly overlapped so that the turn-on voltage is a few hundred mV above the turn-off voltage.  This hysteresis keeps input noise (around the switching threshold) from resulting in multiple output cycles as the transition occurs.   __ Contact: Eric Seale

The SMS remote controller -  It's been passed a lot of years since my first SMS remote control.  The reason I stoped developing the source code of my previous circuit was that the T10s was not available in the market sinse a lot of years.  So,  __ Designed by Vassilis Serasidis

The Ultimate Wireless Volume Control -  17-Aug-11 -Design News:   Andrew Morris decided the usual wireless volume controls donít offer enough functionality, so he created the ultimate volume control that connects between a computer or MP3 player and an amplified speaker system. __ Andrew R. Morris, Gadget Freak-Case #192

The VTSE solar engine -  The VTSE uses the popular 1381 chip and that is its main advantage.  The potentiometer (or two fixed resistors) connects one leg between the output and input of the 1381 and the other leg to the supply voltage.  These resistors acts like a voltage divider when the SE is off and the 1381 output is low.  In that case, the voltage that appears at the 1381 input is determined by the ratio of the pot or the two resistors and is usually set for 2 times rated 1381 voltage.   __ Designed by Wilf Rigter

The Vx2SE solar engine -  The Vx2SE is a simple discrete voltage-doubling SE for driving an LED.  If the load is a red or green LED, J1 is used together with just one red or green LED for threshold detection (no 1381).  For driving a blue LED use two green or red LEDs in series and may require a higher voltage (3V) solar cell.  With 100uf capacitors the flash frequency is 2-3Hz and the R2 and R3 resistors may be omitted.  With very large capacitors (0.01F and up) the frequency is much lower and the resistors can be optimized to stretch the LED "on" time.  The Vx2 solar engines will self trigger but are also sensitive to a drop in light and will trigger from a shadow etc.   __ Designed by Wilf Rigter

Theremin Controller -  Hand and body motions in proximity to the sensing antennas produce frequency changes in a Hartley oscillator operating at approximately 750kHz.  The signal from this variable oscillator is mixed with a constant reference frequency in a ring modulator and the result passed through a single pole of low pass filter to leave only the difference between the variable and reference oscillator frequencies.  The sensing circuitry is duplicated for Pitch and Volume sensor antennas. __ Designed by John Simonton

Thermal Cooling Fan Controller -  As we begin to enjoy those lazy hazy days of summer, the most important thing on most of our minds is how to keep cool during those hot days.  For some of us that means turning up the old air conditioner and sipping on a nice cold glass of our favorite soft drink.  However, we often forget about an equally important __ Designed by Radio Amateur Society of Norwich

Thermal Peak Detection Charger -  The electric model aircraft and car industries have produced a bewildering array of field chargers for NiCd motor battery packs.  These range from simple 6 or 7 cell chargers consisting of a resistor and mechanical timer, to more complex chargers with peak detection, cycling, and the ability to handle 36 cell packs __ Designed by Stefan Vorkoettert

Thermal Techniques in Measurement and Control Circuitry -  Linear Technology AN5 __ Designed by Jim WilliamsDec 1st, 1984

Thermistor Temperature Controller -  Schematic only __ Designed by G.L. Chemelec

Thermo Alarm -  The Th1 thermistor is a regular NTC (Negative Temperature Coeficient) of about 1000 ohms.    But other types will work too.    Adjust the sensitivity with the 20K trim-pot P1.  When the thermistor is at operating temperature, the resistance is high The 330K resistor (R3) is to introduce a little bit hysteresis back on the basis of Q2 to prevent relay chatter __ Designed by Tony van Roon  VA3AVR

Thermocouple Thermometer with Cold Junction Compensation -  The LTC2997 is a high-accuracy analog output temperature sensor. __ Linear Technology/Analog Devices App Note, Jul 7th 2011

Thermofan to Keep Your Amp Cool -  Use a 12V computer fan to cool your amp.    Uses diode temperature sensor f __ Designed by Rod Elliott  ESP

Thermostat  (1N4148) -  This circuit controls very accurately a fan of any size.    Just adjust the associated resistors for a different type and you're all set.    The above circuit diagram is for a small cpu-fan, rated 12V at 12mA current.   __ Designed by Tony van Roon  VA3AVR

Thermostat (NTC) -  The LM3911 requires only a few resistors and capacitors to turn it into a full-function temperature controller.    The schematic diagram illustrates the simplicity of the overal circuit.    The resistor network consisting of R1, R2, and R3 are used to provide the set point voltage for the feedback input of the LM3911 __ Designed by Tony van Roon  VA3AVR

Thermostat Control for Electric Heaters -  One Advantage of these two units is the Sensor can be placed Away from the heater, therefore sensing the Actual Room temperature, not the direct heat from the heater.  These can also be used in a confined space with a Heat Lamp, to create a Drying Oven  __ Designed by G.L. Chemelec

Thermostat for 12v Cooling Fan -  This circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2011

Thermostat for 1KW Space Heater SCR controlled -  Below is a thermostat circuit I recently built to control a 1300 watt space heater.  The heater element (not shown) is connected in series with two back to back 16 amp SCRs (not shown) which are controlled with a small pulse transformer.  The pulse transformer has 3 identical windings, two of which are used to supply trigger pulses to the SCRs, and the third winding is connected to a PNP transistor pair that alternately supply pulses to the transformer at the beginning of each AC half cycle.  The trigger pulses are applied to both SCRs near the beginning of each AC half cycle but only one conducts depending on the AC polarity. __ Designed by Bill Bowden

Third Brake Light -  This circuit is NOT a pulser or flasher! What's so special about this circuit? Well, the first third-brake light I installed I had to pull a wire from the Third Brake Light all the way underneath the carpet to the brake-pedal-switch and I thought it would be easier to pluck the signal of both brakelights via the trunk.  Bench-test your circuit first and apply power to the circuit,  __ Designed by Tonny Von Roon

Third Brake Light Pulser -  Several years ago these flashers were introduced in the automotive industry as part of the third brake light and contained strobe lights   (and strobing continuously for the duration of pressing the break pedal) but got abandoned almost immediately sometime later because of the 'strobe' effect it has on some people.  This circuit has become obsolet since much better circuits are available these days without the 'lag' in between brakes caused by R4 and C3.  One of the circuits is listed below __ Designed by Tony van Roon  VA3AVR

Three Band Equalizer -  Using a single op-amp this easy to make equalizer offers three ranges, low frequency, mid frequency, and high.  With component values shown there is approximately +/-20dB of boost or cut at frequencies of 50Hz, 1kHz and 10kHz.  Supply voltage may be anything from 6 to 30 Volts.  Maximum boost 20dB is only realized with maximum supply voltage __ Designed by Andy Collison

Three Channel Color Organ for a Car -  An Active Filter Design.   __ Designed by G.L. Chemelec

Three Channel Color Organ for a Car -  An Active Filter Design.   __ Designed by G.L. Chemelec

Three Level Audio Power Indicator -  Battery-operated3 LED display that connect it to loudspeaker output __ Contact: Flavio Dellepiane, fladello @ tin.it

Three Volt Universal LED Flasher -  The circuit below will flash any LED color with fixed current pulses powered by a 3v battery.  It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement.  Using this approach, white and . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2008

Three-Channel White-LED Driver Uses Simple Circuit Step-Down DC/DC Converter -  09/13/12  EDN-Design Ideas Drive multiple LEDs with current mirrors from a single step-down converter.   __ Circuit Design by Nora Jacalan Esteves, Technor Semiconductor LLC, Pleasanton, CA

Three-Minute Closet Light -  I have a coat closet by my front door.  The thing is very dark at night and really needs some kind of illumination inside.  I could hire an electrician to install a light in the closet ceiling and then wire it to a toggle switch outside the door but that would cost me quite a bit of money. . . Circuit by David A. Johnson P.E.-December, 2011

Three-Phase Brushless Motor RPM Controller  -  The TPIC43T01/02 is a monolithic motor control integrated Circuit designed to provide RPM control to a 3-phase brushless dc motor.  The device provides two analog sensor input ports which include a speed sensor interface and a Hall effect position interface.  The speed feedback interface consists of an FG amplifier to receive an external sinusoidal signal

Three-phaseProgrammable Controller for ON/OFF Motor -  Automatic on/off controller for a 3-phase electric motor can be made with a programmable time switch.  In this case a maximum of eight time durations can be programmed.  The system has two...__ Electronics Projects for You

Three-Volt Low Battery Voltage Flasher -  Many battery powered devices use two AA alkaline cells.  Often you will not know when it is time to replace the batteries until the device powered by them actually stops operating.  The hobby circuit below can be connected to a 3v battery, to give you some . . . Hobby Circuit designed by David Johnson P.E.-January, 1998

Three-Volt Powered Super Bright LED Flasher -  I have posted several kinds of LED flashers over the years.   This is yet one more flasher, designed to flash any high power LED of any color.  It hits the LED with a 25ms 250ma pulse once every 2 seconds.   This works out to an average current about 3ma.  It . . . Hobby Circuit designed by David Johnson P.E.-April, 2009

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Control Circuits:   #'s - A       B - C       D - G        H - L       M - P        Q - S        T - U        V - Z

 


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