Cell Phone Jammer Using IC555

A Simple Cell phone jammer using IC555.

GSM Controlled Robot

In the project the robot is controlled by a mobile phone that makes a call to the mobile phone attached to the robot. In the course of a call, if any button is pressed a tone corresponding to the button pressed is heard at the other end called ‘Dual Tone Multiple frequency’ (DTMF) tone.

8x8 Dotmatrix Scrolling LED Display

Here 64 leds which are connected to an Matrix display. The Anodes are drived through an Driver IC UDN2981 and the cathodes are drived through ULN2803. The Atmega8515 is used in this project to control the display. The microcontroller is programmed with Bascom AVR.

Infrared Remote Switch

A Simple Infrared remote control circuit.

Portable CD Player Adapter For Car Circuit

Whenever I'm in the car listening to my favourite CD, it always happens; my batteries go dead. To solve that problem, I built this extremely simple regulator circuit. It steps down the 12V from the lighter socket to 9V which is used by the CD player. Different CD players (I have a Sony Discman) may require different voltages, so just use the correct regulator. All the 78xx series regulators have the same pin out, so the circuit is universal.

Schematic-


Parts List-
C1 - 1 - 1000uF 25V Electrolytic Capacitor
C2 - 1 - 10uF 25V Electrolytic Capacitor
C3 - 1 - 1uF 15V Elextrolytic Capacitor
C4 - 1 - 0.1uF 15V Electrolytic Capacitor
U1 - 1 - 7809 Or Other Regulator (See "Notes")
MISC - 1 - Cigarette Lighter Plug, Plug For CD Player (See "Notes"), Heat Sink For U1, Wire, Case.

Notes-
1) The voltage your CD player needs will determine which regulator you use. For 9V, use the 7809. For 6V, use the 7806. For the unlikely 5V use the 7805. Remember that whatever regulator you use, you will need to heat sink it. The metal case or metal cover on the case makes a great heat sink.

2) I built the circuit in a small case with the long wire to the cigaratte lighter plug coming out one end, then another, slightly shorter wire going out the other end to the CD player.

3) Triple check your wiring. You would hate to ruin an expensive CD player because you reversed one of the connections or hooked the regulator up backwards.

Light/Dark Detector Circuit

This handy little circuit can tell the difference between darkness and light, making it very useful for switching on and off signs, porch lights or other things when it gets dark or light.

Schematic-

Parts List-
R1 - 1 - 100K Pot
Q1 - 1 - 2N3904 NPN Transistor
Q2 - 1 - NPN Phototransistor
RELAY - 1 - 9V Relay
MISC - 1 - Board, Wire, 9V Battery Snap (if battery used), Knob For R1

Notes-
1) R1 Adjusts sensitivity

IR Remote Control Jammer Circuit

Don't like your little brother's TV channel selection? Hate the volume your wife sets the stereo at? Want to just annoy someone? This circuit does all that and more by jamming most IR remote signals. The circuit releases a flood of pulsing IR light that confuses the reciever by corrupting the data stream.

Schematic-

Parts List-
R1 - 1 - 100K 1/4W Resistor
R2 - 1 - 150K 1/4W Resistor
R3 - 1 - 10K 1/4W Resistor
R4 - 1 - 1K 1/4W Resistor
R5 - 1 - 22 Ohm 1/4W Resistor See "Notes"
C1 - 1 - 10nF Ceramic Disc Capacitor
C2 - 1 - 1uF Electrolytic Capacitor
D1, D2, D3 - 3 - High Output IR LED
Q1 - 1 - 2N4403 PNP Transistor
Q2 - 1 - 2N4401 NPN Transistor
S1 - 1 - Normally Open Momentary Push Botton
B1 - 1 - 4.5V Battery (Three "AA"'s In Series)
MISC - 1 - Wire, Case, Board

Notes-
1) You may need to adjust the value of R3 for the right frequency. A pot can be used.

2) You may only need one IR LED.

3) It goes without saying that this circuit should be used with descretion.

4) The value of R5 depends on your supply voltage and LED. For a standard 4.5V supply and standard IR LED, use 22 Ohm as specified on the parts list. This forum topic covers this resistor as well as a few other issues with the circuit.

Dual Polarity Power Supply Circuit

This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts. It is great for powering op amp circuits, as well as other circuits that require a dual supply voltage.

Schematic-

Parts List-
C1, C2 - 2 - 2200uF 35V Electrolytic Capacitor
C3, C4, C5, C7 - 4 - 1uF 35V Electrolytic Capacitor
C6, C8 - 2 - 100uF 35V Electrolytic Capacitor
R1, R4 - 2 - 5K Pot
R2, R3 - 2 - 240 Ohm 1/4 W Resistor
BR1 - 1 - 2A 30V Bridge Rectifier
U1 - 1 - LM317 Adjustable Positive Regulator
U2 - 1 - LM337 Adjustable Negative Regulator
T1 - 1 - 30V Center Tapped 2 Amp Transformer
S1 - 1 - SPST 2 Amp Switch
MISC - 1 - Heatsinks For U1 And U2, Line Cord, Case, Knobs For Pots, Wire

Notes-
1) Since this project operates from 120 (or 220, or 240, etc.) volts AC, it MUST be built inside a case.

2) U1 and U2 get quite hot and will require heatsinks. A fan is usually not needed.

3) You can, of course, add a volt and amp meter.

4) U1 and U2 can only go down to a minimum of +-1.2V. If you need to go lower, you can add two 1N4003 diodes in series with the output of the regulator. The diodes drop about 0.6V each, which will allow the supply to go to 0. Note that this will also decrease your maximum output voltage by 1.2V. (Thanks to Steve Horvath for the suggestion).

Car Battery Charger

This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the battery is fully charged, the circuit switches off and lights a LED, telling you that the cycle has finished.

Schematic-

Parts List-
R1 - 1 - 500 Ohm 1/4 W Resistor
R2 - 1 - 3K 1/4 W Resistor
R3 - 1 - 1K 1/4 W Resistor
R4 - 1 - 15 Ohm 1/4 W Resistor
R5 - 1 - 230 Ohm 1/4 W Resistor
R6 - 1 - 15K 1/4 W Resistor
R7 - 1 - 0.2 Ohm 10 W Resistor
C1 - 1 - 0.1uF 25V Ceramic Capacitor
C2 - 1 - 1uF 25V Electrolytic Capacitor
C3 - 1 - 1000pF 25V Ceramic Capacitor
D1 - 1 - 1N457 Diode
Q1 - 1 - 2N2905 PNP Transistor
U1 - 1 - LM350 Regulator
U2 - 1 - LM301A Op Amp
S1 - 1 - Normally Open Push Button Switch
MISC - 1 - Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output

Notes-
1) The circuit was meant to be powered by a power supply, which is why there is no transformer, rectifier, or filter capacitors on the schematic. There is no reason why you cannot add these.

2) A heatsink will be needed for U1.

3) To use the circuit, hook it up to a power supply/plug it in. Then, connect the battery to be charged to the output terminals. All you have to do now is push S1 (the "Start" switch), and wait for the circuit to finish.

4) If you want to use the charger without having to provide an external power supply, use the following circuit.

5) The first time you use the circuit, you should check up on it every once and a while to make sure that it is working properly and the battery is not being over charged.

Load Sensing Power Switch Circuit

This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current draw of the "master" device through a low value high wattage resistor using a comparator. The output of that comparator then switches on the "slave" relay. The circuit can be built into a power bar, extension cord or power center to provide a convenient set of "smart" outlets that switch on when the master appliance is powered (turn on the computer monitor and the computer, printer and other peripherals come on as well).

Schematic-

Parts List-
C1, C3 - 2 - 10uF 35V Electrolytic Capacitor
C2 - 1 - 1uF 35V Electrolytic Capacitor
R1 - 1 - 0.1 Ohm 10W Resistor
R2 - 1 - 27K 1/2W Resistor
R3, R4 - 1 - 1K 1/4W Resistor
R5 - 1 - 470K 1/4W Resistor
R6 - 1 - 4.7K 1/2W Resistor
R7 - 1 - 10K 1/4W Resistor
D1, D2, D4 - 3 - 1N4004 Rectifier Diode
D3 - 1 - 1N4744 15V 1 Watt Zener Diode
U1 - 1 - LM358N Dual Op Amp IC
Q1 - 1 - 2N3904 NPN Transistor
K1 - 1 - Relay, 12VDC Coil, 120VAC 10A Contacts
S1 - 1 - SPST Switch 120AVC, 10A
MISC - 1 - Board, Wire, Socket For U1, Case, Mains Plug, Socket

Notes-
1. This circuit is designed for 120V operation. For 240V operation, resistors R2 and R6 will need to be changed.

2. A maximum of 5A can be used as the master unless the wattage of R1 is increased

3. S1 provides a manual bypass switch.

4. THis circuit is not isolated from the mains supply. Because of this, you must exercise extreme caution when working around the circuit if it is plugged in.

Automatic 12V Lead Acid Battery Charger Circuit

This charger will charge any 12V lead acid battery including flooded, gel and AGM. It is fully automatic and will charge at a rate up to about 4A until the battery voltage reaches a preset point at which it will switch to a very low current float charge. If the battery voltage drops again the charger will begin charging until the voltage once again reaches the cut off point. In this way it can be left connected to a battery indefinitely to maintain full charge without causing damage. An LED indicates when the battery is fully charged.

Schematic-

Parts List-
R1, R3 - 2 - 330 Ohm 1/4W Resistor
R2 - 1 - 100 Ohm 1/4W Pot
R4, R5, R7, R8 - 4 - 82 Ohm 2W Resistor
R6 - 1 - 100 Ohm 1/4W Resistor
R9 - 1 - 1K 1/4W Resistor
C1 - 1 - 220uF 25V Electrolytic Capacitor
D1 - 1 - P600 Diode Any 50V 5A or greater rectifier diode
D2 - 1 - 1N4004 Diode 1N4002, 1N4007
D3 - 1 - 5.6V Zener Diode
D4 - 1 - LED (Red, Green or Yellow)
Q1 - 1 - BT136 TRIAC
Q2 - 1 - BRX49 SCR
T1 - 1 - 12V 4A Transformer See Notes
F1 - 1 - 3A Fuse
S1 - 1 - SPST Switch, 120VAC 5A
MISC - 1 - Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output, Fuse Holder

Notes-
1. R2 will have to be adjusted to set the proper finish charge voltage. Flooded and gel batteries are generally charged to 13.8V. If you are cycling the battery (AGM or gel) then 14.5V to 14.9V is generally recommended by battery manufacturers. To set up the charger, set the pot to midway, turn on the charger and then connect a battery to it's output. Monitor the charge with a voltmeter until the battery reaches the proper end voltage and then adjust the pot until the LED glows steadily. The charger has now been set. To charge multiple battery types you can mount the pot on the front of the case and have each position marked for the appropriate voltage.

2. Q1 will need a heatsink. If the circuit is mounted in a case then a small fan might be necessary and can generally be powered right off the output of D1.

3. T1 is a transformer with a primary voltage appropriate to your location (120V, 220V, etc.) and a secondary around 12V. Using a higher voltage secondary (16V-18V) will allow you to charge 16V batteries sometimes used in racing applications.

4. If the circuit is powered off, the battery should be disconnected from it's output otherwise the circuit will drain the battery slowly.

6V to 12V Converter Circuit

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

Schematic-

Parts List-

R1, R4 - 2 - 2.2K 1/4W Resistor
R2, R3 - 2 - 4.7K 1/4W Resistor
R5 - 1 - 1K 1/4W Resistor
R6 - 1 - 1.5K 1/4W Resistor
R7 - 1 - 33K 1/4W Resistor
R8 - 1 - 10K 1/4W Resistor
C1,C2 - 2 - 0.1uF Ceramic Disc Capacitor
C3 - 1 - 470uF 25V Electrolytic Capcitor
D1 - 1 - 1N914 Diode
D2 - 1 - 1N4004 Diode
D3 - 1 - 12V 400mW Zener Diode
Q1, Q2, Q4 - 3 - BC547 NPN Transistor
Q3 - 1 - BD679 NPN Transistor
L1 - 1 - See Notes
MISC - 1 - Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

Notes-
1. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.

2. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.

3. You can use a larger value for C3 to provide better filtering.

4. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

Time Delay Relay Circuit

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use.

Schematic-

Parts List-

R1 - 1 - 1 Meg Pot
R2 - 1 - 10 K 1/4 Watt Resistor
C1 - 1 - 10uf 25V Electrolytic Capacitor
C2 - 1 - 0.01uf Ceramic Disc Capacitor
D1,D2 - 2 - 1N914 Diodes
U1 - 1 - 555 Timer IC
RELAY - 1 - 9V Relay
S1 - 1 - 1A 120V SPST Switch
MISC - 1 - Board, Wire, Socket For U1

Notes-
1. R1 adjusts the on time.

2. You can use a different capacitor for C1 to change the maximum on time.

3. S1 is used to activate the timing cycle. S1 can be replaced by a NPN transistor so that the circuit may be triggered by a computer, other circuit, etc.

Voltage Inverter

This simple circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components, so it doesn't add much in the way of size and cost to a project.

Schematic-


Parts List-
R1 - 1 - 24K 1/4 Watt Resistor
R2 - 1 - 56K 1/4 Watt Resistor
C1 - 1 - 3300pF 25V Ceramic Capacitor
C2 - 1 - 47uF 25V Electrolytic Capacitor
C3 - 1 - 10uF 25V Electrolytic Capacitor
C4 - 1 - 100uF 25V Electrolytic Capacitor
D1, D2 - 2 - 1N4148 Silicon Diode
U1 - 1 - 555 Timer
MISC - 1 - Wire, Board

One Tube Regenerative Radio Circuit

A regenerative radio works by feeding back a small amount of amplified output of the detector back into the input. Thus it achieves sensitivity far beyond what only a detector could alone. This simple regen radio uses a single tube as it's detector and amplifier; the "Audion". It's a great first project for those wishing to bring back some nostalgia by building one of the first amplified radio sets. Built on a board using point to point wiring and a set of period headphones, it can be a great functional conversation piece.

Schematic-

Parts List-
R1 - 1 - 50K Linear Taper Pot
R2 - 1 - 2.2 Meg 1/4W Resistor
R3 - 1 - 10K 1/4W Resistor
C1 - 1 - 250pF 100V Ceramic Disc Capacitor
C2 - 1 - 365pF Air Variable Tuning Capacitor
C3, C4 - 2 - 120pF 100V Ceramic Disc Capacitor
C5 - 1 - 0.1uF 100V Ceramic Disc Capacitor
V1 - 1 - 3A4 Audion Tube 3S4, 3Q4 (See Notes)
L1 - 1 - 30 Turns 26 AWG Magnet Wire (See Notes)
L2 - 1 - 80 Turns 26 AWG Magnet Wire (See Notes)
L3 - 1 - 20 Turns 26 AWG Magnet Wire (See Notes)
S1 - 1 - SPST Switch
HEADPHONE - 1 - High Impedance Headphones (2K or Greater)
ANT1, ANT2 - 2 - See Notes
MISC - 1 - Board, Wire, Sockets For V1, Case, Knob for R1, Clips for Antenna and Batteries.

Notes-
1. L1 - L3 are constructed on the same coil form. A toilet paper tube will be the coil form. Secure the 26 AWG wire to the form by punching two holes close together and winding the wire once around the "bridge" between them. Alternately, just a drop of hot glue can be used. Leave about 6" of wire. Wind on twenty turns close together but never overlapping. Make a tap by securing the wire with a drop of glue and twisting a loop. This is L3. Wind 80 more turns in the same direction and then secure the end, leaving about 6" of wire at the end. This is L2. Now secure the 26 AWG wire 1/8" from the end of L2 and wind 30 turns in the same direction as the other coils, making sure that this coil is spaced 1/8" evenly from L2. Secure the end and leave about 6" lead. This is coil L1. Now trim the extra length of the coil form and spray the coil with several coats of lacquer to hold the wires in place.

2. R1 and S1 can be one unit if you purchase a pot with a built in switch. This will avoid turning the set on with full regen and causing a nasty squeal from the headphones.

3. The 3S4 or 3Q4 can be substituted for the 3A4 in the connections of pin 3 and pin 4 are swapped.

4. An antenna of only a few feet can be used for ANT1 for easy indoor installation. Far better is an antenna of 50 feet or more outside, which would be connected to ANT2.

5. Note that this circuit requires a good Earth ground. A suitable location is a metal cold water pipe.

6. To use the set, place C2 at about midway, set R1 fully counterclockwise and then turn on S1 and allow the tubes several seconds to warm up. Increase R1 until the headphones squeal, then back off. That is when the set is most sensitive. Now tune C2 to the desired frequency. You may have to readjust R1 as you tune different frequencies. With some practice you will figure out how much regen you need as you change stations.

7. If R1 seems to have no effect, swap the connections to L1.

Single Chip AM Radio

The ZN414 IC contains an entire automatic gain controlled AM receiver in a small three pin package. With only a few external components, a simple radio with excellent selection and reception can be constructed. Since the chip also uses a low supply voltage of only 1.3V, 3V coin cell battery can make for a physically small circuit with many covert uses. The chip has a wide bandwidth of between 150KHz and 3MHz, so by playing with values in the tuning circuit you can pick up a wide variety of signals.

Schematic-

Parts List-
R1 - 1 - 100K 1/4W Resistor
R2 - 1 - 470 Ohm 1/4W Resistor
R3 - 1 - 1K 1/4W Resistor
C1 - 1 - 0.04uF Ceramic Disc Capacitor
C2 - 1 - 365pF Variable Tuning Capacitor
C3 - 1 - 0.01uF Ceramic Disc Capacitor
D1, D2 - 2 - 1N4148 Signal Diode
U1 - 1 - ZN414 Radio IC MK484
L1 - 1 - See Notes
MISC - 1 - Board, Holder For Batteries, Wire, Coil Form For L1

Notes-
1. The ZN414 is obsolete. The MK484 is it's replacement, but like all special purpose ICs, it can be hard to find. At the time of this writing, there are many suppliers online that carry the IC. The ZN416 is functionally the same but with the additiion of a built in headphone amplifier.

2. L1 is made by winding 40 turns of 28 AWG magnet wire around a 4" non-magnetic coil form. Cardboard tubes or paper cups are ideal forms.

3. The audio output of the circuit is about 0.1V peak to peak, which will drive a set of crystal earphones or other very high impedance phones. A small audio amplifier made with an LM386 will allow you to use modern dynamic headphones or a small speaker.

4. L1, C1 and C2 are the tuning circuit. By changing them around, you can change the range of frequencies the radio is capable of. Easiest to change is L1. Simply by altering the number of coils or moving the windings farther apart, you can shift the circuit to different frequency ranges.

Simple Two Speed Contactor DC Motor Controller

The simplest of all motor controllers (besides a straight on/off switch) is the contactor controller. I designed this contactor controller for use in my electric scooter project. It is based around three 12V relays, two 12V batteries, two switches and of course a motor. Having no silicon to "fry", it is quite reliable and robust. A contactor controller works by rearranging the two (or more) supply batteries between series and parallel. This gives the motor a slow speed (batteries in parallel, current adds) and a fast speed (batteries in series, voltage adds). This assures that both batteries are discharged equally. When the circuit is "at rest", the batteries are connected in parallel, which allows easy recharging.

Schematic-

Parts List-

K1, K2, K3 - 3 - 12V 30A SPDT Relay (See Notes)
S1, S2 - 2 - SPST Switch or Button
B1, B2 - 2 - 12V Battery (See Notes)
M1 - 1 - 12V or 24V Motor (See Notes)
MISC - 1 - Case, Wire, etc.

Notes-
1. S1 closes K3 and thus causes M1 to operate. S2 activates K1 and K2, reconfiguring the batteries for series operation and thus causes M1 to operate at "fast" speed.

2. B1 and B2 should be chosen based on the current requirements of M1. Often, sealed lead-acid type batteries are available at local suppliers for surprisingly low prices. These batteries are ideal for things such as scooters, go-karts, etc.

3. The relays are standard automotive type relays, available cheaply from any auto parts store.

4. Your motor will depend on your requirements. 12V motors will normally run fine at 24V, and vice versa.

5. You will notice that in series mode, all three relays only pull power from B2. This is because the relays have 12V coils, and it is impossible to switch the batteries from series to parallel and keep power to the coils at the same time. This does, however, mean that B2 is discharged slighty before B1. This should normally not be an issue unless the batteries are being drained completely "dead". Draining a battery dead is not good for it in any situation, and should be avoided. If you wish, you can use a small 12V battery to run the relays separately.

6. You can add two more speeds to this controller using the schematic below. It connects at points A and B shown above on the controller schematic.


K1 is simply another of the same relay as used in the controller. S1 is another switch. R1 needs to be chosen based on your motor, but it will be of low value (under 10 Ohm) and high wattage (normally at least 100W). It must be capable of handling the full current drawn by the motor. This is not exactly an efficient way to limit current to the motor as excess current is dissipated as heat by the resistor, so it is normally only used for a "starter" speed.

Simple Servo Controller Circuit

Schematic-

Parts List-
R1 - 1 - 820 Ohm 1/4W Resistor
R2 - 1 - 68K 1/4W Resistor
R3 - 1 - 10K 1/4W Resistor
R4 - 1 - 1K 1/4W Resistor
R5 - 1 - 1K Linear Taper Pot
C1 - 1 - 1uF 16V Electrolytic Capacitor
Q1 - 1 - 2N3904 NPN Transistor 2N2222, Most Small Signal Transistors
U1 - 1 - 555 Timer IC
MISC - 1 - Board, Wire, Knob For R1, 8 Pin Socket For U1

Notes-
1. R1 adjusts the position of the servo.

2. Connect the servo to the circuit as shown in the schematic. For common Futaba servos, the red wire is power, the black wire is ground, and the white wire is control.

Polarity Tester Circuit


Parts List-
R1 - 1 - 1K 1/4W Resistor
D1 - 1 - Green LED
D2 - 1 - Red LED
D4, D5, D6, D7 - 4 - 1N4001 Silicon Diode
MISC - 1 - Board, Wire, Case, Probes

Notes-
1. Email Dudley LeRoux with questions, comments, etc.

2. To use the circuit, just connect your probes to the source under test. If D1 lights up, the left most probe (on the schematic) is connected to positive. The opposite is true if the left probe is negative. If both LEDs are on, the source being probed is AC.

3. Be careful when using this tester not to probe a source greater than about 12V.

Pine Racecar Victory Judge


Parts List-
R1, R2 - 2 - 100 Ohm 1/4W Resistor
R3, R4 - 2 - 100K 1/4W Resistor
D1, D2 - 2 - Standard LED
SCR1, SCR2 - 2 - 6A, 200V SCR (such as the 106B)
S1, S2 - 2 - See Notes
K1 - 1 - Small 12V Relay
MISC - 1 - Board, Wire

Notes

1. S1 and S2 are small lever type micro switches. Most any kind will do, as long as they are sensitive enough to be activated by the wheels of the cars. They should be positioned on the track so that the front wheels of the cars will run over them as the cars just cross the finish line.

2. To reset the circuit, disconnect and then reconnect power. You can add a normally closed switch in series with the power supply to make this easier.

3. There is no reason this circuit cannot be used to tell the winner of a foot race, bike race, slot car race, etc.

Low Voltage Alarm


Parts List-
R1, R3 - 2 - 1K 1/4W Resistor
R2 - 1 - 5K Pot
U1 - 1 - LM339 Op Amp IC
D1 - 1 - 1N5233B Zener Diode
D2 - 1 - LED
BZ1 - 1 - Piezo Buzzer
MISC - 1 - Board, wire, socket for IC

Notes-
1. The circuit will operate from 9V to 12V.
2. Adjust R2 until the alarm goes off at the correct voltage.

Simple Air Flow Detector


Parts List-

R1 - 1 - 100 Ohm 1/4W Resistor
R2 - 1 - 470 Ohm 1/4W Resistor
R3 - 1 - 10k 1/4W Resistor
R4 - 1 - 100K 1/4W Resistor
R5 - 1 - 1K 1/4W Resistor
C1 - 1 - 47uF Electrolytic Capacitor
U1 - 1 - 78L05 Voltage Regulator
U2 - 1 - LM339 Op Amp
L1 - 1 - #47 Incandescent lamp with glass removed (See "Notes")
D1 - 1 - LED
MISC - 1 - Board, Wire, Sockets for ICs, etc.

Notes-
1. The glass will have to be removed from L1 without breaking the filament. Wrap the glass in masking tape and it in a vise. Slowly crank down until the glass breaks, then remove the bulb and carefully peel back the tape. If the filament has broken, you will need another lamp.

Simple Touch Switch


Parts List -
R1 - 1 - 10 Meg 1/4W Resistor
R2 - 1 - 47K 1/4W Resistor
R3 - 1 - 120k 1/4W Resistor
R4 - 1 - 470 Ohm 1/4W Resistor
C1 - 1 - 15uF Electrolytic Capacitor
D1 - 1 - 1N4007 Silicon Rectifier Diode
Q1 - 1 - 2N5458 N Channel Field Effect Transistor
Q2 - 1 - 2N2222 NPN Transistor 2N3904
Q3 - 1 - 2N3906 PNP Transistor
K1 - 1 - Relay w/12V Coil, Contacts To Suit Application
MISC - 1 - Board, Wire, Small Metal Pad For Touch Pad

Notes
1. The touch pad can be most easily made by cutting a small square of PCB material and then soldering on a single wire. Alternatively, something like a penny glued to a plastic backing will do the job.

2. As mentioned, a latching relay can be used so that a momentary touch activates the relay and it remains active. To turn off a latching relay, power must be interrupted. So a 2nd circuit with a normal relay can be used to cut power (use the NC contacts on the 2nd circuit). Placed side by side, two touch pads form an "on" and an "off" pad.

Simple Lie Detector Circuit


Parts List-
R1 - 1 - 33K 1/4W Resistor
R2 - 1 - 5K Pot
R3 - 1 - 1.5K 1/4W Resistor
C1 - 1 - 1uF 16V Electrolytic Capacitor
Q1 - 1 - 2N3565 NPN Transistor
M1 - 1 - 0-1 mA Analog Meter
MISC - 1 - Case, Wire, Electrodes (See Nots)

Notes
1. The electrodes can be alligator clips (although they can be painful), electrode pads (like the type they use in the hospital), or just wires and tape.

2. To use the circuit, attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions. You know the subject is lying when the meter changes.

Rain Detector Circuit


Parts List -
R1 - 1 - 1K 1/4 W Resistor
R2 - 1 - 680 Ohm 1/4 W Resistor
D1 - 1 - 1N4001 Silicon Diode
BZ1 - 1 - 12V Buzzer
S1 - 1 - SPST Switch
SCR1 - 1 - C106B1 SCR 106CY
SENSOR - 1 - See Notes
MISC - 1 - Board, Wire, Case, PC Board (For Sensor)

Notes

1. The sensor is a small piece of PC board etched to the pattern showen in the schematic. The traces should be very close to each other, but never touching. A large spiral pattern would also work.

2. Make sure to use a loud buzzer.

3V LED Chaser


General
There are many 9V chaser circuits that seem to waste about 7V when driving LEDs that are only about 2V. This project is unique, because it uses only two inexpensive alkaline battery cells totaling 3V for power. Since most of the waste is eliminated, the cells last a long time.
Unlike the other circuits, this one flashes the LEDs for only about 30ms each, further extending the battery life. For user convenience, it has a stepper speed control and a brightness control. At slower speeds and with reduced brightness, the battery life is further extended considerably.
Mounted in a circle, the LEDs appear to rotate as they step from one to the next.

Specifications
· Battery: Two alkaline cells (AA size were used in the prototype)
· Pulse Width Modulation frequency: 1.4KHz very bright to 6KHz very dim
· LED current: 15mA pulses, reduced to 10.5mA at maximum Pulse Width Modulation
· LED voltage drop: 1.76V (measured, not rated) @ 10.5mA
· Minimum battery voltage (total of both cells):
<1.24V, circuit is running but LEDs are not lit 1.6V, LEDs are very dim at maximum brightness 2.0V, LEDs reach almost full brightness, battery replacement is recommended. · Radio interference: None Circuit Description
The 74HC Cmos ICs are rated for a 2V to 6V power supply for high-speed logic circuits. They continue to operate at a much lower voltage but no longer meet high-speed logic specifications. To reach high speeds, their output current can momentarily exceed 400mA (low voltage drop) but thermal considerations limit maximum continuous output current to 20mA. Perfect for driving LEDs!

· IC2 is a 10 stage Johnson counter/decoder. On the rising edge of each clock pulse its outputs step one-at-a-time. It drives the anode of each conducting LED toward the positive supply.
· IC1a is a standard Cmos inverter Schmitt-trigger oscillator with C3 and C4 totaling 800nF for a very slow step rate. R2 is the speed control pot with R1 limiting its maximum speed. It clocks IC2 and feeds the inverters/drivers. D1 and R3 reduce its output high time to 30mS.
· IC1d, IC1e, IC1f and IC1b are paralleled inverter/drivers for a low output voltage drop and drive the emitter of T1 to ground.
· IC1c is another standard Cmos inverter Schmitt-trigger oscillator. R5 is its Pulse Width Modulation control and with D3 performs dimming of the LEDs. D2 and R4 extend the PWM’s maximum pulse width.
· T1 is a transistor that is used as a PWM switch. R7 limits maximum LED pulse current.
· C1 bypasses the battery’s supply voltage at low frequencies and C2 bypasses at high frequencies.

Construction
The ten LEDs mount on a Compact-Disc which is glued to a plastic box with contact cement. The box houses the Veroboard circuit in its lower main part with the battery holder in its lid. Multiconductor ribbon cable joins the LEDs to the circuit. The pots mount on the sides of the box.

Parts List
1 - IC1 - CD74HC14N or SN74HC14N High-speed Cmos, Schmitt-trigger hex inverters
1 -IC2 - CD74HC4017N or SN74HC4017N High-speed Cmos, decade counter-decoder
1 - T1 - 2N3904 or 2N4401 NPN transistor
10 - LEDs - MV8191 High brightness, wide angle red LED (less than 2V)
3 - D1 to D3 - 1N4148 or 1N914 Silicon diode
2 - R1, R3 - 100K 1/4W resistor
1 - R2 - 1M Linear–taper potentiometer (speed)
1 - R4 - 330K 1/4W resistor
1 - R5 - 1M Audio-taper (logarithmic) potentiometer (brightness)
1 - R6 - 680 1/4W resistor
1 - R7 - 22 1/4W resistor
1 - C1 - 100uF/10V or 100uF/16V Electrolytic capacitor
1 - C2 - 0.1uF/50V or 0.1uF/100V Ceramic disc capacitor
1 - C3 - 330nF/63V Metalized poly capacitor
1 - C4 - 470nF/63V Metalized poly capacitor
1 - C5 - 1nF/100V Metalized poly capacitor
2 - misc. Alkaline battery cells
1 - misc. - Battery holder
1 - misc. - Compact Disc
1 - misc. - Hole plug for the CD’s center hole
1 - misc. - Plastic box
3 - misc. - Vinyl feet for box
2 - misc. - Knobs for potentiometers
1 - misc. - 9 to 11 conductor ribbon cable

Notes
1) The ICs are manufactured by Texas Instruments, and others.
2) The LEDs are manufactured by Fairchild Semiconductor.
3) Above manufacturers offer free samples.

Digital Keypad Combination Lock


Parts-
C1 - 1 - 1uF 25V Electrolytic Capacitor
C2 - 1 - 220uF 25V Electrolytic Capacitor
R1 - 1 - 2.2K 1/4W Resistor
Q1 - 1 - 2N3904 NPN Transistor
D1 - 1 - 1N4148 Rectifier Diode
K1 - 1 - 12V SPDT Relay Any appropriate relay with 12V coil
U1 - 1 - LS7220 Digital Lock IC
S1-S12 - 12 - SPST Momentary Pushbutton Keypad (see notes)
HD1 - 1 - 12 Position Header

Notes-
1. To set the combination, wire the appropriate switches to U1 pins 3, 4, 5 and 6 using the header. For example if S1 was connected to pin 3, S2 to pin 4, S3 to pin 5 and S4 to pin 6, the combination would be 1,2,3,4. Now wire all other unused switches across the header to pin 2 of U1. In this way you can create any 4 digit combination you want. Pin 2 is the reset pin, so connecting all unused keys to it assures that the entire combination must be reentered if an incorrect key is pressed.

2. When the appropriate combination is entered, the relay is activated for a period of time determined by C1. The 1uF capacitor specified in the parts list will result in an on-time of roughly 5 seconds. Increase the value of C1 to increase this time.

3. An easy way to make a keypad is to buy 12 PC board mount pushbuttons and then etch a PC board so that the buttons are in 4 rows of 3, similar to a telephone keypad. Place this in a case and then use a label maker or transfer letters to add your numbers to the tops of the pushbuttons. You can also use a pre made keypad but keep in mind that you need a pad which provides an output for each key. Most pads available have the keys connected to provide a row and column signal when they are pressed.

AC Motor Speed Controller


Parts List -
R1 - 1 - 27K 1W Resistor
R2 - 1 - 10K 1/4W Resistor
R3 - 1 - 100K 1/4W Resistor
R4 - 1 - 33K 1/4W Resistor
R5 - 1 - 2.2K 1/4W Resistor
R6 - 1 - 1K 1/4W Resistor
R7 - 1 - 60K Ohm 1/4W Resistor
R8 - 1 - 3K Linear Taper Trim Pot
R9 - 1 - 5K Linear Taper Pot
R10 - 1 - 4.7K Linear Taper Trim Pot
R11 - 1 - 3.3K 1/4W Resistor
R12 - 1 - 100 Ohm 1/4W Resistor
R13 - 1 - 47 Ohm 1W Resistor (See Notes)
C1, C3 - 2 - 0.1uF Ceramic Disc Capacitor
C2 - 1 - 100uF 50V Electrolytic Capacitor
D1 - 1 - 6V Zener Diode
Q1 - 1 - 2N2222 NPN Transistor 2N3904
SCR1 - 1 - ECG5400
TR1 - 1 - TRIAC (See Notes)
U1 - 1 - DIAC Opto-Isolator (See Notes)
BR1, BR2 - 2 - 5A 50V Bridge Rectifier
T1 - 1 - Transformer (See Notes)
MISC - 1 - PC Board, Case, Line Cord, Socket For U1, Heatsinks

Notes
1. TR1 must be chosen to match the requirements of the load. Most generic TRIACs with ratings to support your load will work fine in this circuit. If you find a TRIAC that works well, feel free to leave a comment.

2. U1 must be chosen to match the ratings of TR1. Most generic DIAC based opto-isolators will work fine. If you have success with a specific part, feel free to leave a comment.

3. T1 is any small transformer with a 1:10 turns ratio. The circuit is designed to run on 120V so a 120V to 12V transformer will work. Alternately, you can wind T1 on a transformer core using a primary of 25 turns, a secondary of 200 turns, and 26 gauge magnet wire.

4. R9 is used to adjust motor speed. R10 is a trim pot used to fine tune the governing action of the circuit. R8 fine tunes the feedback circuit to adjust for proper voltage at the gate of SCR1. It should be adjusted to just past the minimum point at which the circuit begins to operate.

5. R13 must be chosen to match the load. Generally, larger loads will require a smaller value.

6. Since this circuit is not isolated from mains, it must be built in an insulated case.

LED Thermometer

LED thermometer is designed for in home use, to read temperatures between about 60 and 78 degrees Fahrenheit. It is based around a precision temperature sensor IC, the LM34DZ. This sensor require no calibration and can measure temperatures of between -50F and +300F. While the circuit shown here does not use the full range of that sensor, it can be modified to do so by simply changing the voltage reference to U2 at the sacrifice of precision.


Parts List-
C1 - 1 - 1uF 25V Electrolytic Capacitor
C2 - 1 - 10uF 25V Electrolytic Capacitor
R1 - 1 - 2.2K 1/4W Resistor
R2, R5, R7 - 3 - 1K Trim Pot
R3 - 1 - 1K 1/4W Resistor
R4 - 1 - 1.5K 1/4W Resistor
R6 - 1 - 470 Ohm 1/4W Resistor
R8 - 1 - 100 Ohm Or 15 Ohm 1/4W Resistor (See Notes)
D1 - D10 - 10 - LED
U1 - 1 - LM34DZ Precision Fahrenheit Temperature Sensor
U2 - 1 - LM3914 Bar/Dot Graph Driver IC
MISC - 1 - Board, Wire, Socket For U1 and U2, Case

Notes-

1) The pinout of U1 depends on the version of the IC you purchase. These options are shown below:
Pinout of LM34 IC variants

2) You will want to build the circuit with U1 and U2 in sockets in order to be able to complete calibration (which requires removal of these ICs).

3) You can use any LED you want for D1 - D10, however blue LEDs have a higher voltage requirement so if you want to go blue for a modern look, they may appear more dim then red, yellow or green.

4) By leaving pin 9 of U2 disconnected, the graph will operate in dot mode and R8 should be 100 Ohm. If you build the circuit with pin 9 tied to 9V, the circuit will be in graph mode and R8 should be 15 Ohms.

5) To calibrate the circuit, you will need a voltmeter. Power the circuit up and let it sit for a few minutes for temperature to stabilize. Ground the negative lead of the meter and connect the positive lead to pins 6 and 7 of U2. Set R7 so the meter reads as close to 3.345V as possible. Now connect the positive lead of the meter to pin 4 of U2 and adjust R5 until the meter reads 2.545V. Finally, disconnect power to the circuit and remove U1 and U2 from their sockets. Measure the value of R3 with an ohmmeter and remember that value. Connect the ohmmeter across R1 and adjust R1 to a value of exactly 3 times the value of R3. Reinstall U1 and U2 and the circuit is ready for use.

Electronic Dice Circuit

Schematic -


Parts List -

R1, R5, R6 - 3 - 22K 1/4W Resistor
R2 - 1 - 10K 1/4W Resistor
R3 - 1 - 4.7K 1/4W Resistor
R4 - 1 - 150K 1/4W Resistor
R7 - R13 - 7 330 Ohm 1/4W Resistor
C1 - 1 - 1uF Electrolytic Capacitor
C2 - 1 - 4.7uF Electrolytic Capacitor
D1 - 1 - 1N4148 Signal Diode
D2 - D8 - 7 - Red/Green/Yellow LED
Q1 - 1 - 2N3904 NPN Transistor
U1 - 1 - 555 Timer IC
U2 - 1 - 74LS192 4 Bit Counter IC
U3 - 1 - 74LS08 Quad Intengreted AND Gate IC
S1 - 1 - SPST Momentary Pushbutton Switch
MISC - 1 - Board, Wire, Sockets For ICs, Case

Notes -
1. Pushing and holding S1 causes the LEDs to rapidly cycle. Releasing the button locks the pattern and shows a number from 1 to 6.

2. When building the circuit, make sure to position the LEDs as shown on the schematic. Otherwise the pattern of the dice will look weird.

3. Two circuits can of course be both powered by one switch to make a dual dice.

7 Segment LED Counter Circuit

Schematic -

7 Segment Reference -

Parts List -
R1-R7 - 7 - 470 Ohm 1/4 Watt Resistor
U1 - 1 - 74LS90 TTL BCD Counter IC
U2 - 1 - 74LS47 TTL Seven Segment Display Driver IC
DISP1 - 1 - Common Anode 7 Segment LED Display
MISC - 1 - Board, Sockets For ICs, Wire

Notes -
1. All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground.

2. You can add more digits by building a second (or third, or fourth, etc...) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

12V to 120V Inverter Circuit


Parts -
C1, C2 - 2 - 68 uf, 25 V Tantalum Capacitor
R1, R2 - 2 - 10 Ohm, 5 Watt Resistor
R3, R4 - 2 - 180 Ohm, 1 Watt Resistor
D1, D2 - 2 - HEP 154 Silicon Diode
Q1, Q2 - 2 - 2N3055 NPN Transistor (see "Notes")
T1 - 1 - 24V, Center Tapped Transformer (see "Notes")
MISC - 1 - Wire, Case, Receptical (For Output)

Notes
1. Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.

2. The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each.

3. Remember, when operating at high wattages, this circuit draws huge amounts of current. Don't let your battery go dead :-).

4. Since this project produces 120 VAC, you must include a fuse and build the project in a case.

5. You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.

6. This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.

7. If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.

TRIAC Light Dimmer

Schematic -

Parts List -
R1 - 1 - 50K Pot
R2 - 1 - 15K 1/2W Resistor
C1, C2 - 2 - 0.068 250V Capacitor
L1 - 1 - Lamp To Be Controlled (up to 350 watts)
L2 - 1 - Neon Lamp
TR1 - 1 - 40502 TRIAC
MISC - 1 - Case, Knob, Heatsink For TR1, Wire, Socket For L1

Notes -

1. This circuit is for 117VAC only. 220 or 240 V will burn up the circuit. L1 can be a maximum of 350 watts.

2. The circuit must be installed and used in a case.

Strobe Light Circuit

Schematic -

Parts List -
R1 - 1 - 10 Meg, 1/4 Watt Resistor
D1, D2 - 2 - 1N4003 Silicon Diode
C1, C2 - 2 - 10uF 350V Capacitor
C3 - 1 - 0.1uF 400 Volt Mylar Capacitor
T1 - 1 - 4KV Trigger Transformer (see "Notes")
FT - 1 - Flash Tube (see "Notes")
L1 - 1 - Neon Bulb
Q1 - 1 - 106 SCR
S1 - 1 - 115V 1A SPST Switch
MISC - 1 - Case, Wire, Line Cord

Notes -
1. This ciruits is NOT isolated from ground. Use caution when operating without a case. A case is required for normal operation. Do not touch any part of the circuit with the case open or not installed.

2. Most any diodes rated at greater then 250 volts at 1 amp can be used instead of the 1N4003's.

LED Chaser

Schematic -

Parts List -
R1 - 1 - 1 Meg 1/4W Resistor
R2 - 1 - 100K Pot
R3 - 1 - 1K 1/4W Resistor 220Ohm if using blue LEDs
C1 - 1 - 0.1uF 16V Ceramic Disk Capacitor
U1 - 1 - 4011 CMOS NAND Gate
U2 - 1 - 4017 CMOS Counter
LED1-10 - 10 - LEDs Of Any Colour
MISC - 1 - Board, Sockets For ICs, Knob For R2

Notes
1. Use R2 to adjust the "chase rate".

2. You may need to use a lower value resistor if you wish to use blue LEDs. Try 220 Ohm.

3. You can also use incandescent lamps instead of LEDs. Use transistors to drive them by connecting the base of the transistors to each of the outputs of the 4017 through a 1K resistor. Connect one end of the lamp to the positive supply. Then connect the other end to the collector of the transistor. The emitter then goes to ground. Depending on the lamps, you may need power transistors that are heat sinked.

4. C1 may be replaced with a larger value for a slower "chase rate".

5. If you have problems with weird circuit behavior, try replacing R1 with a 33K resistor, and increasing C1 to 1uF.

6. If you plan to use this circuit in your car, be warned that in some areas it is illegal to have red, blue or yellow flashing lights unless you are an emergency vehicle.

LASER Transmitter/Receiver

This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc..). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself.

Schematic of Transmitter -

Schematic of Receiver -

Parts -
C1, C2 - 2 - 0.1uf Ceramic Disc Capacitor
C3 - 1 - 100uf 25V Electrolytic Capacitor
R1 - 1 - 100K Ohm 1/4W Resistor
R2 - 1 - 1M Ohm 1/4W Resistor
R3 - 1 - 10K Pot
Q1 - 1 - NPN Phototransistor
U1 - 1 - 741 Op Amp
U2 - 1 - LM386 Audio Amp
SPKR1 - 1 - 8 Ohm Speaker
T1 - 1 - 8 Ohm:2K Audio Transformer
MISC - 1 - Wire, Board, Knob For R3, LASER Tube and Power Supply

Notes
1. In the transmitter schematic, no ballast resistor is shown because most small LASER power supplies already have one built in. Yours may differ, and a resistor may be needed.

2. The receiver should be kept away from bright lights. You may want to put a piece of wax paper in front of Q1 to keep the LASER from swamping it.

3. In order to get any decent amount of modulation, you may need to drive T1 with more then a watt.

4. The circuit can be made to transmit computer data with the use of two modem chips.

Infrared Remote Switch Circuit

PCB Layout -

Schematic


PCB Parts Placement

Parts List -
R1 - 1 - 3 Meg 1/4W Resistor
R2 - 1 - 1.2 Meg 1/4W Resistor
R3 - 1 - 680 Ohm 1/4W Resistor
R4 - 1 - 2K 1/4W Resistor
R5 - 1 - 4.7K 1/4W Resistor
R6 - 1 - 150 Ohm 1/4W Resistor
C1 - 1 - 0.001uF Ceramic Disc Capacitor
C2, C5 - 2 - 1uF 50V Tantalum Electrolytic Capacitor
C3 - 1 - 47uF 50V Tantalum Electrolytic Capacitor
C4 - 1 - 10uF 50V Tantalum Electrolytic Capacitor
C5 - 1 - 150 Ohm 1/4W Resistor
D1 - 1 - 1N4733 5V Zener Diode
D2 - 1 - 1N4003 Rectifier Diode
Q1 - 1 - 2N6071A TRIAC
U1 - 1 - GP1U52X IR Module
U2 - 1 - MC74HC74 D-Type Flip Flop
U3 - 1 - MOC3011 Opto Isolator
MISC - 1 - Board, Sockets For ICs, Mains Socket, Mains Plug and Cord, Wire

Notes
1. Under normal circumstances, Q1 should not need a heatsink.
2. The circuit is designed for a supply voltage of 120V.
3. The printed circuit pattern is reproduced here larger then real life for clarity. It will need to be resized to the scale at the bottom of the image if you intend to transfer it to a board.
4. The circuit functions as an on/off flip flop. Illuminate it with your remote once to turn it on, then again to turn it off.


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Courtsy-simple-electronics.com

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