High voltage stun gun

Read before building:
This device produces high voltage pulses discrupting muscles and nervous sYstem, leaving anyone who touches it in a state of menthal confusion. Can be used agains ferocious animals or attackers, BUT REMEMBER, this device may be illegal in your state (for eg where I live, these devices are banned). It is quite dangeros for peoples experiencing cardiac problems, and for electronic equipment (like peacemakers), since it generates some RF. Don't attept irresponsible actions with this device, it is not a toy.

After the introduction let's pass to the circuit.

The 555 IC is wired as a astable to produce square wave with adjustable freq and duty cycle (notice the potentiomenters and diode). This square wave is feed to a IRF840 Mosfet (no need of totem transistors since freq is low and the IC has enough current capability to rapidly charge/discharge the gate). As a substitute of the mosfet, a bipolar transistor can be used (and a 100ohm resistor between 555 and base of the transistor). Valid BJT can be BU406, but also smaller BJT can be ok, keep in mind that it must handle at least 2A continuous. The inductive kick snubber isn't needed because the power is low and it is almost totally adsorbed to charge the tank capacitor, in addition since this device is battery operated we don't want to dissipate the power on a resistor but we want it in sparks. With a snubbing network you will experience lower firing rates. USE A PUSHBUTTON SWITCH FOR SAFETY

Construction of T2: this is the real boring part. Since it is unlikely to find it in shops we need to build them. Materials needed: enamel copper wire (0,20 mm or 0,125 mm), ferrite stick, LDPE sheets (0,25 mm). Secure the ferrite stick with a layer of ldpe (polyethilene, as a substiture use electric insulating tape) and glue it (or tape it) Place 200-250 windings on the ldpe (even more windings if the stick is more than 1'), another ldpe layer, another 200-250 windings and so on to finally have 5-6 layers (approx 1000-1400 turns but even more doesn't hurt performance, but be careful for internar arcing that will ruin it). Insulate it again and place the primary winding, 15-20 turns of 1mm wire are just ok, too much windings (too mush resistance and inductance) will lead to smaller current and smaller spike in T2 secondary because of lower rise time,and too few will not saturate the core. I chosen MKP capacitors because they have low ESR and ESL (they are widely used in tesla coils as mmc capacitors).

The spark gap can be simple two crossed (but not touching) 1 mm spaced wires. It acts as a voltage controlled switch, firing when
the voltage is enough to ionize the air between them (turning it to plasma with small resistance). Keep in mind that it would
be wise do place it into a small plastic container and fill with oil letting bubbles out (don't use motor oir or frying oil
but pure mineral oil which has no water in it.

Disclaimer: As i have seen before, IT IS NOT A TOY, DON'T DO ANYTHING STUPID WITH IT. I DON'T ACCEPT ANY RESPONSIBILITY OF DAMAGES DONE TO OTHER PEOPLE OR YOURSELF WITH THIS DEVICE. IF YOU WANT TO BUILD IT YOU MUST ACCEPT THIS CONDITION. Using the procedures described above would prevent you from any damages/troubles. Don't carry it in streets or public places if they are banned in your country, and don't use it near electronic devices. As the wise man says use it like a deterrent, even against animals.

Light/dark detector

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 ligh

Parts:

	Part		Total Qty.	Description	Substitutions
	R1		1	100K Pot
	Q1		1	2N3904 NPN Transistor	2N2222
	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

Park aid

Parts:

R1_____________10K   1/4W Resistor
R2,R5,R6,R9_____1K   1/4W Resistors
R3_____________33R   1/4W Resistor
R4,R11__________1M   1/4W Resistors
R7______________4K7  1/4W Resistor
R8______________1K5  1/4W Resistor
R10,R12-R14_____1K   1/4W Resistors


C1,C4___________1΅F  63V Electrolytic or Polyester Capacitors
C2_____________47pF  63V Ceramic Capacitor
C3,C5_________100΅F  25V Electrolytic Capacitors

D1_____________Infra-red LED
D2_____________Infra-red Photo Diode (see Notes)
D3,D4________1N4148  75V 150mA Diodes
D5-7___________LEDs  (Any color and size)

IC1_____________555  Timer IC
IC2___________LM324  Low Power Quad Op-amp
IC3____________7812  12V 1A Positive voltage regulator IC

Device purpose:

This circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall.
All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device's sensitivity.
Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.

Circuit operation:

IC1 forms an oscillator driving the infra-red LED by means of 0.8mSec. pulses at 120Hz frequency and about 300mA peak current. D1 & D2 are placed facing the car on the same line, a couple of centimeters apart, on a short breadboard strip fastened to the wall. D2 picks-up the infra-red beam generated by D1 and reflected by the surface placed in front of it. The signal is amplified by IC2A and peak detected by D4 & C4. Diode D3, with R5 & R6, compensate for the forward diode drop of D4. A DC voltage proportional to the distance of the reflecting object and D1 & D2 feeds the inverting inputs of three voltage comparators. These comparators switch on and off the LEDs, referring to voltages at their non-inverting inputs set by the voltage divider resistor chain R7-R10.

Notes:

• Power supply must be regulated (hence the use of IC3) for precise reference voltages. The circuit can be fed by a commercial wall plug-in power supply, having a DC output voltage in the range 12-24V.

• Current drawing: LEDs off 40mA; all LEDs on 60mA @ 12V DC supply.

• The infra-red Photo Diode D2, should be of the type incorporating an optical sunlight filter: these components appear in black plastic cases. Some of them resemble TO92 transistors: in this case, please note that the sensitive surface is the curved, not the flat one.

• Avoid sun or artificial light hitting directly D1 & D2.

• If your car has black bumpers, you can line-up the infra-red diodes with the (mostly white) license or number plate.

• It's wiser to place all the circuitry near the infra-red LEDs in a small box. The 3 signaling LEDs can be placed far from the main box at an height making them well visible by the car driver.

• The best setup is obtained bringing D2 nearer to D1 (without a reflecting object) until D5 illuminates; then moving it a bit until D5 is clearly off. Usually D1-D2 optimum distance lies in the range 1.5-3 cm.

• If you are needing a simpler circuit of this kind driving a LED or a relay, click Infra-red Level Detector

Speed limit alert

Parts:

R1,R2,R19_______1K   1/4W Resistors
R3-R6,R13,R17_100K   1/4W Resistors
R7,R15__________1M   1/4W Resistors
R8_____________50K   1/2W Trimmer Cermet
R9____________470R   1/4W Resistor
R10___________470K   1/4W Resistor
R11___________100K   1/2W Trimmer Cermet (see notes)
R12___________220K   1/4W Resistor (see notes)
R14,R16________68K   1/4W Resistors
R18____________22K   1/4W Resistor
R20___________150R   1/4W Resistor (see notes)

C1,C7_________100΅F  25V Electrolytic Capacitors
C2,C3_________330nF  63V Polyester Capacitors
C4-C6___________4΅7  25V Electrolytic Capacitors

D1,D5______Red LEDs  3 or 5mm.
D2,D3________1N4148  75V 150mA Diodes
D4________BZX79C7V5  7.5V 500mW Zener Diode

IC1__________CA3140  or TL061 Op-amp IC
IC2____________4069  Hex Inverter IC
IC3____________4098  or 4528 Dual Monostable Multivibrator IC

Q1,Q2_________BC238  25V 100mA NPN Transistors

L1_____________10mH  miniature Inductor (see notes)

BZ1___________Piezo sounder (incorporating 3KHz oscillator)

SW1____________SPST  Slider Switch

B1_______________9V  PP3 Battery (see notes)

Clip for PP3 Battery

Device purpose:

This circuit has been designed to alert the vehicle driver that he has reached the maximum fixed speed limit (i.e. in a motorway). It eliminates the necessity of looking at the tachometer and to be distracted from driving.
There is a strict relation between engine's RPM and vehicle speed, so this device controls RPM, starting to beep and flashing a LED once per second, when maximum fixed speed is reached.
Its outstanding feature lies in the fact that no connection is required from circuit to engine.

Circuit operation:

IC1 forms a differential amplifier for the electromagnetic pulses generated by the engine sparking-plugs, picked-up by sensor coil L1. IC2A further amplifies the pulses and IC2B to IC2F inverters provide clean pulse squaring. The monostable multivibrator IC3A is used as a frequency discriminator, its pin 6 going firmly high when speed limit (settled by R11) is reached. IC3B, the transistors and associate components provide timings for the signaling part, formed by LED D5 and piezo sounder BZ1. D3 introduces a small amount of hysteresis.

Notes:

• D1 is necessary at set-up to monitor the sparking-plugs emission, thus permitting to find easily the best placement for the device on the dashboard or close to it. After the setting is done, D1 & R9 can be omitted or switched-off, with battery saving.

• During the preceding operation R8 must be adjusted for better results. The best setting of this trimmer is usually obtained when its value lies between 10 and 20K.

• You must do this first setting when the engine is on but the vehicle is stationary.

• The final simplest setting can be made with the help of a second person. Drive the vehicle and reach the speed needed. The helper must adjust the trimmer R11 until the device operates the beeper and D5. Reducing car's speed the beep must stop.

• L1 can be a 10mH small inductor usually sold in the form of a tiny rectangular plastic box. If you need an higher sensitivity you can build a special coil, winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Extract the coil from the former and tape it with insulating tape making thus a stand-alone coil.

• Circuit's current drawing is approx. 10mA. If you intend to use the car's 12V battery, you can connect the device to the lighter socket. In this case R20 must be 330R.

• Depending on the engine's cylinders number, R11 can be unable to set the device properly. In some cases you must use R11=200K and R12=100K or less.

• If you need to set-up the device on the bench, a sine or square wave variable generator is required.

• To calculate the frequency relation to RPM in a four strokes engine you can use the following formula:
  Hz= (Number of cylinders * RPM) / 120.
  For a two strokes engine the formula is: Hz= (Number of cylinders * RPM) / 60.
  Thus, for a car with a four strokes engine and four cylinders the resulting frequency @ 3000 RPM is 100Hz.

• Temporarily disconnect C2 from IC1's pin 6. Connect the generator's output to C2 and Ground. Set the generator's frequency to i.e. 100Hz and regulate R11 until you hear the beeps and LED D5 flashes. Reducing the frequency to 99 or 98 Hz, beeping and flashing must stop.

• This circuit is not suited to Diesel engines.