Need help with remote firework detonator

[cmartin303]

(NOTE: Please forgive my terminology, I'm not well versed with electronics lingo. This is my first project; I have a programming background so most of the logic is the same.)

Hey guys, I'm currently working on making a remote firework detonator using a walkie talkies. I've run into a problem that I'm not quite sure how to solve. What my plan was originally was to solder wires to the speaker output on the walkie talkies, and use a relay to switch on current from an array of four AA batteries. The power from the batteries would be enough to light the fireworks (I need about 6VDC - 12VDC).

I've soldered the wires to speaker outputs, but the voltage coming from them it very low (about .1 VDC); which is not enough electricity to trip the relay I have. I cannot find any lower voltage relays anywhere. Anyone have any other ideas to how I could accomplish this?

 

[BobK]

That is a really bad idea since it could be triggered by some other walkie talkie, or interference.

Bob

 

[cmartin303]

That is a really bad idea since it could be triggered by some other walkie talkie, or interference.

Bob

I know that is a potential flaw, but I am putting in an arming switch to mitigate that risk. The likely hood of someone using a walkie talkie in my area, at the same moment I'm going to be detonating fireworks are slim to none.

 

[KrisBlueNZ]

I tend to agree with Bob. Walkie talkies are designed to allow kids to have fun, not to be a secure form of communication. And it's not just other walkie talkies that could trigger your igniter.

You could probably improve reliability by sending a specific signal, e.g. a tone at high amplitude, and implementing a delay at the receiver, so only a constant, loud signal for two seconds would trigger the igniter. Whether that would be safe enough, I don't know.

Detecting that signal at the receiver would require some circuitry. Simplest option would be a tuned circuit made from an inductor and a capacitor tuned to the tone frequency, driving a transistor or MOSFET, driving the relay coil. The circuit could be powered from the walkie talkie's power supply.

What voltage does the walkie talkie use?

Does one side of the speaker connect to the negative of the battery?

 

[KJ6EAD]

What radios are you using?

If you're using FM FRS or GMRS types you can use their CTCSS squelch system in conjunction with a DTMF at both ends to give you some noise and false trigger immunity.

 

[KrisBlueNZ]

Good idea KJ6EAD. CTCSS plus DTMF would be fairly reliable. Good thinking.

 

[galaxy]

Why not just use one of the multitude of UHF remotes available on ebay etc.
Encoded stream, relay output etc. Some quite long range.