VIDEO OF IT IN ACTION!
This is a simple how-to guide on making a cheap remote/wireless ignition for a spud gun or other application. It uses a doorbell circuit to transmit an RF signal to activate a relay that completes a 9V stun gun circuit, turning it on. Can be made for less than $20.
Components (you don't have to use the exact model part as I have, any with the same specs will do):
1x Arlec 149 door chime (any wireless door chime will do)
1x 100uF 10V capacitor (10ML100MEFC6.3X5)
1x 1A 200V standard diode (1N4003)
2x SPDT on/off toggle switch
1x key on/off switch
1x momentary button
1x project box
1x 3V DPDT relay (IM01TS)
1x 100kV stungun
Box of jewellers screwdrivers (not required but helps when fiddling with small parts)
Heat shrink (not required but is recommended)
Credit for the two circuitry diagrams and alternative relay wiring graphic, Spudfiles member: dewey-1
Step 1: Modifying the Door Chime
My particular door chime receiver was powered using two AA batteries in series, providing 3 volts. I used a voltmeter to measure the output when the door chime was activated and it too was 3V. If you don't have a voltmeter, don't worry as your output will probably match the circuitry voltage.
Determine the voltage applied to the circuitry of your door chime receiver, some are 3V some may be higher like 5V. Doesn't matter which voltage it is, any will do.
First, you need to cut the two wires that are going to the speaker. Once that is done, determine which wire is positive and which is negative by connecting them to an LED, voltmeter or other electrical component that can tell you the polarity. Another way is by finding the transistor near one of the wire terminals, it seems that the transistor is generally connected to the negative wire.
Next, we need to determine which relay we need. The relay is an electrically operated switch, when a low powered signal is sent to a relay, it closes a switch and allows the signal to carry on to the rest of the circuit. In this case, the relay will be completing the circuit of a stungun. When you attach a 9V to your stungun circuit, it should spark continuously but if we put a relay between the 9V positive terminal and the stungun positive terminal, the stungun can't spark until the relay has been activated.
If your door chime circuit is also 3V, find a 3V relay similar to the one I used (model number is on the components list).
Step 2: Project Box and Theory
Drill 11mm holes in the top of the project box and thread the two toggle switches, the key switch and momentary button in to their respective holes.
When the door chime transmitter (the unit with a button) sends a signal to the door chime receiver, it sends a low voltage signal to the two speaker wires which we have cut from the speaker. When wired to a relay, it will send a signal through the relay, activating it, this completes the relay circuit by connecting relay contact #4 and relay contact #3 and allows the signal from the 9V battery to go to the stun gun. The signal from the receiver will be applied for about 3-5 seconds, after which the signal stops and the relay closes. This means your stungun will spark for 3-5 seconds.
A problem with the door chime is that its signal pulsates (peaks and drops) , to stop this we use a capacitor to build up a small charge which is applied when the signal is momentarily dropped in one of the pulses. A 100uF 10V capacitor worked for me and should work for you too. Any capacitor of these specifications should do although I have listed the exact one I used on the intro page.
To protect the receiver circuit from a high voltage spike from the relay, we will also need a diode in the circuit. If you don't understand why we need one, don't worry about it, just follow the instructions. I used a 1A 200V diode, model number is on the first page. The diode will be connected "backwards", positive wire to the cathode and negative wire to the anode.
Step 3: Wiring the Receiver Circuit to the Relay
Solder the positive wire from the receiver circuit to the positive pole of the capacitor (generally, the longer of the two poles), solder the negative wire from the receiver to the negative pole of the capacitor. Solder a wire from the positive side of the capacitor to the NEGATIVE side of the diode (the negative side, cathode, usually has a black ring around it) and solder a wire from the negative pole of the capacitor to the positive side of the diode.
In the diagram below that shows the complete circuit wiring, the blue circle is the capacitor and the pink rod is the diode.
My relay had 8 contacts, yours may have less. Spec sheets for whatever relay you get should be available and tell you which poles you need to connect the wires to.
In this case, I solder the wire from the positive side of the diode (this is the negative wire) to relay contact #8, I then solder the wire from the negative side of the diode (this is the positive wire) to relay contact #1. As per the diagram below (the diagram with the "was" and "will be"), I solder a wire to contact #3 and then solder the other end to the positive wire coming off the stun gun. I then solder a wire to contact #4 and solder the other end to one terminal on a SPDT toggle switch. The other terminal of this SPDT toggle switch will have a wire soldered to it going to the key switch then the 9V stun gun circuit battery.
Note: If your relay is normally open, refer to the other diagram where the wire going to contact #4 is soldered to contact #2 instead.
Full circuitry diagrams below as well as an alternative way of wiring the capacitor and diode to the relay.
Step 4: Other Wiring
Now the relay and receiver are all wired up, we just need to wire the toggles, key switch and momentary button. This allows us to trigger the stungun manually instead of with the door chime remote.
As per the diagram below, solder the wire from relay contact #4 to one of the SPDT toggle switch contacts. Solder another wire from the second contact on the toggle going to one of the key switch contacts. On this same key switch contact, soldering another wire that leads to a contact on the second toggle switch. Solder a wire from the spare contact on the second toggle switch to a contact on the momentary button. Solder another wire to the spare contact on the momentary button to the positive terminal on the stun gun.
As shown in the diagram below, one key switch contact should have two wires coming from it, both leading to a toggle each.
Now solder a wire to the spare contact on the key switch and connect this to the positive terminal of the 9V battery.
To finish up, solder the negative wire from the 9V battery to the negative terminal on the stun gun.
Test the circuit turning the key switch on and flicking the toggle switch on, then press the transmitter door chime button. This should activate the relay, joining contact #4 and contact #3, completing the 9V circuit to the stun gun and creating a spark on the stungun output.
Step 5: Finishing
If heat shrink was used when soldering, you shouldn't have to worry about any wiring short circuiting when stuffed inside a project box. If you didn't use heat shrinker, use electricians tape to cover any exposed wires.
Use foam, rubber, polystyrene or similar to fill the spaces inside the project box. This stops the circuits rolling around and potentially disconnecting wires. To help prevent wires from becoming detaches, use superglue to glue them to a circuit or the project box or another wire to help relieve the soldered contact of any stress brought on from wires bending (i.e., if you solder a wire to a contact and push the end of the wire forwards, it will bend and put a lot of strain on where it is soldered to the contact, too much strain and it will break off. If you superglue the wire to something else, it will put the strain on this glued joint and not the contact).
If the circuit is not working, be sure to meticulously check every contact for either detached wires or short circuiting. If you still can't find out why the circuit is not working, use a voltmeter to see where the break in the circuit is..