Ways to use an FM system.

[they call me 9 fingers]

Here is a quick layout. Note the relay can be replaced with a transistor, that would probably work better

[Boomer]

I can't open the schematic.

 

And about the headphone signal triggering a relay, I doubt it. Unless it' several volts output (= more than 2 AA batteries) and the relay is extremely low-power (like Siemens/Epcos P1 at 5V/375Ohms or below). Better use the transistor.

 

Is the radio auto-mute if nothing is received? Even then, if it's analog transmission some static/random noise (from car ignition to garage remote) may be over the threshold, and you are called no-fingers.

 

While we're at it, I sent you a pm.

[they call me 9 fingers]

Yeah random noise/interferance is definatly a concern with most modern radios their is a auto squeltch funtion wich work resonably well, the bigest concern that i see would be when the radio is turned on or when the headphone jack is pluged in, as this sometimes causes static/crackles as long as you were careful when ataching every thing t would be resonably safe. I cant take full credit for the idea, when i was in iraq the road side bombs would use a similar system they usually replaced the radio with a cell phone. true story, one of our detainees was setting a road side bomb that was cell detonated when his wife called the phone that he was using ( she wanted him to pick something up at the store), now he is in prision missing a ear. SO defiate procautions are needed with something like this. I would like to expand this type of system to run on multiple channels allowing more than one ignition. just some ideas

[GalFisk]

You could make a safety mechanism, consisting of a delay circuit that keeps the unit from firing until a set time has elapsed. The delay is started either by turning the unit on or by a separate arming switch, and the circuit indicates (by light and/or sound) when time's up and it's ready to fire.

If you have more than one channel, you could use one of them to shut off the reciever as well. A fail safe shutoff could consist of a relay, where the current to hold the relay closed goes through its own contacts. When this current is interrupted, the relay opens and the whole circuit loses power.

This should also reset the delay circuit.

[whitefox77]

As a licensed HAM radio operator, this may be the only topic on this forum I feel I have any real expertise in.

 

Using an RC car controller or garage door opener for a remote is a bad idea. Either one can be tripped too easily for there to be any kind of safety margin. The garage door opener is the better of the two idea, but there are still only a few hundred codes. Not worth risking fingers.

 

I actually read something on radio-wave remote detonators a couple years ago (before I got into pyro). I don't remember exactly what it said the minimum legal length of the signal was, but I remember thinking that it was excessively long. The equivalent of over a kilobyte of information. Keep in mind we're still talking about a signal that is sent in a split second. This "code" is then matched against a code on the receiver unit, and if they don't match, no fire. I would think a signal with the complexity of 25 byte equivlant (about 15 times more than is used in even advanced RC aircraft) would provide a good safety margin.

 

Where as an RC car simply needs the signal to be on the correct frequency, with the correct carrier tone. The equivalent of 1 byte.

 

If you want to go wireless, I recomend infra-red (aka TV remote), not radio. It is MUCH less likely to suffer from interference problems, as IR is line-of-site only, and has a very limited range (only a couple hundred feet at best).

 

If you want an electric start, the safest rout is wired. It's also the cheepest and most reliable.

[FrankRizzo]

There are a number of Chinese eBay sellers who carry very inexpensive 1, 4, 8, & 12 relay boards and remotes with considerable range. I think you're much better off spending a few more bucks on something like those units.

 

This seller is wonderful:

 

Electronics Made in China

 

or

 

http://www.e-madeinchn.com/Product.htm

[they call me 9 fingers]

Actually those look like they might have some real potential, i might have to wait till pay day and try one of those bad boys out. Not as fun as creating your own personal frankenstin but hey. Hey whitefox what is your call sign, I used to be kb0uku but sadly when i went to college i let it expire, i need to get it renewed.

[they call me 9 fingers]

There are a number of Chinese eBay sellers who carry very inexpensive 1, 4, 8, & 12 relay boards and remotes with considerable range.  I think you're much better off spending a few more bucks on something like those units.

 

This seller is wonderful:

 

Electronics Made in China

 

or

 

http://www.e-madeinchn.com/Product.htm

So I just spent some time looking over their site. These little systems would work great. They already have a code sytem built in so that will drasticly cut down interferance. Secondly they have multiple channels I think it would be pretty easy to get a 8 channel togle reciever and wire two channels in series that way you have to turn both on berfore your circute is compleated. I would think that would be safe enough for your average guy who just wants to shoot off some rocket volleys or what not, I dont know if I would use it for HE though. Any ways just my 2cents