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Subject: Re: Computer Controlled Pyrotechnic Firing Panel
Date: Tue, 3 Sep 2002 22:56:56 -0700
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Thanks for the post. I do plan on using a keyed switch that cuts power to
the whole circuit. I have built a few electrical firing panels (none
computer controlled) and always use keyed switches for the power. In some I
have also use dip switches that have to be in the up position before you can
press the momentary pushbutton switch to supply the igniter with
electricity. That is a little overboard and can add to the cost but it's
nice to be safe.
I'm always safe and don't plan on just grabbing all of these parts and start
building this system by trial and error. I am here to get ideas for the
system and even then I will check out all of the ideas given by doing my own
research. I know there are several pro's here but I don't believe you
should ever just take someone's word for it, you should always double check
their ideas as even pro's sometimes make mistakes. :-)
I would also like to incorporate the piezo buzzer at the field units as that
is a nice warning to GET AWAY if you are near and find out why some idiot is
supplying power to the units while you're still out there.
"Dave VanHorn" wrote in message
> The main thing that I would caution you on, is that you design in a
> dual-redundant safety mechanism that absolutely prevents ignition until it
> is explicitly bypassed.
> I've done some ignition controls for rocketry (not model rockets) and
> I go a bit overboard, but then agian, I've never had a problem.
> The general approach that I use is that there has to be two different
> mechanisms to prevent ignition, that require manual intervention. For
> example, my launch controller uses a key switch (a real one, not a PC
> cabinet thing) and two momentary buttons. I have to turn the key to apply
> any power at all to the system. The two pushbuttons must be depressed at
> the same time to effect a launch.. When the key is turned, a loud piezo
> siren sounds at the remote head, located at the pad.
> When saftied, there is no source of current to the remote head, and the
> ignitor is shorted out at the remote head, preventing any current that
> past the first safety from firing the ignitor.
> If you handle the lockouts properly, then the worst the PC can do is fire
> the wrong devices at the wrong time. That's maybe expensive and
> but not fatal.
> What I'd imagine in your application is a number of remote heads, each
> it's own local safties, then a master safety that requires that all local
> safties be off before it can be turned off. You would activate each head
> you leave the field, in a planned "escape route".
> The touchy part is verifying a good ignition circuit.
> That can't be done any other way than putting current through the
> The trick of course is to make absolutely sure that there is no possible
> to get anywhere near the firing current, even with a fault in the circuit.
> From what I've seen, crewing a couple of shows, you might have 10-100+
> ignitors in the system, and this certainly gets complicated.
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