This circuit will guide you in constructing very simple yet useful circuit. The purpose of this circuit is to make it more safe to play with fire crackers or fireworks. Use your imagination to put it into the right use. Please use caution when dealing with such kind of devices as this may cause harm or injury. Use at your own risk, I am not responsible of any consequences of using this circuit and/or assembly. Also observe the rules of your local area before use.

  You need the following to build the circuit:

1. Two fresh batteries each 9 volts
2. Relay - coil should operate on 4 to 9 volts DC
3. Diode type 1N4148
4. Any NPN transistor such as 2N2222
5. Normally open switch - mount inside small box
6. Long wire - or long 2-parallel line cable - 18 to 22 AWG gauge. Make sure not shorted and new.
7. Two 4.7 K ohm resistors - from Radio shack or other place.
8. 1 Mega ohm resistor - you may need many more, depending on how many loads you are playing with!
9. 100 ohm resistor
10. 3 inch of Nichrome wire 26 gauge (you may need more length for multiple use.)

You need some soldering skills to construct this circuit on small PCB board. Make sure you build the circuit without any mistake. One Mega ohm resistor (item 8 above) is used to hold the nichrome wire and is helpful for this job. You may use other valuse than 1 Mega ohms but not lower than few K Ohms, such as 10 K ohms and over (preferably). The longer the wires the safer it is, don't go 1 mile though! May be 10 to 30 meters may do it. Of course less than 10 meters will do it also but not as safe, so do it at your own risk.

You may place the PCB board inside a little box and leave the 1 Mega ohm resistor leads coming out from the box to wrap the Nichrome wire around them. You may also extend the 1 Mega ohm resistor leads by soldering extra wires (10 to 20 inch wires off the 1 Mega resistor leads) so they can hang outside the box for easy access. This is important so when the cracker pops the electronics won't get damaged.

Make your own load: Another way of doing it is to get one more 1 Mega ohm resistor (item 8 above) and wrap the extra Nichrome wires on its two exposed leads after you wrap the middle section of Nichrome wire on the cracker fuse first. Now use the wire alligator clips from the electronic box to connect to the load, two exposed leads of the 1 Mega ohm resistor, you just made. Hmmm, you know what to do next! If you have large cracker make sure you extend the wire cable first. Later I will teach you how to make your own wireless remote control to use instead of the wires, you can then pop you things from 100 meters away or even further. Come back again…

Once you build the circuit wrap the Nichrome wire around a piece of match instead of the cracker fuse. Press and hold the switch for at least 3 seconds untill you see the Nichrome wire gets hot and red. After this verification use the cracker, wrap the nichrome wire around the fuse (3 to 6 turns) then wrap the edges of the remaining Nichrome wires around the conductive leads of 1 Mega ohm resistor. Make sure that you wrap wires properly since Nichrome wires may not be soldered on the resistor leads. Extend the long wire and press to close the switch (hold for 3 seconds or so) until you hear the cracker pops. Disconnect batteries when not in use.

If battery 2 ages or wires become too long the circuit may not work properly, in this case reduce the value of 100 ohms to around 50 ohms and/or reduce the value of the 4.7 K ohm resistor connecting to the switch to any value between 2K ohm to 4 K ohms.

In the diagram below make sure that you have enough length of wires where it says "Long Wire / Keep Safe." See instructions above.

to Index