altimeter arming ?

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shockwaveriderz - 26 Sep 2004 20:57 GMT

does anybody use any form of "continuty" checking within their altimeter
circuits to make sure it is "on" "ARMED", that checks the ejection charge
circuits to make sure they will fire? I was thinking along the lines of
something you could temporarily plug into a small socket on the side of the
bidy tube? perhaps led indictaor of some sorts?

looking for ideas,suggestions.,techniques,recommendations
especially real-life experiences..

you can email me direct
TIA

shockie B)

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Phil Stein - 26 Sep 2004 21:44 GMT

>does anybody use any form of "continuty" checking within their altimeter
>circuits to make sure it is "on" "ARMED", that checks the ejection charge
[quoted text clipped - 9 lines]
>
>shockie B)

I'm not certain if this is what you're asking - most if not all
altimiters have a way of letting you know if it sees continuity on the
pyro channels.

Also, if you shunt your pyros until you are ready to launch, you'll be
safer & a properly designed shunt ckt will allow you to test the pyro
channels without an ignitor attached.

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Glen Overby - 29 Sep 2004 16:05 GMT

>Also, if you shunt your pyros until you are ready to launch, you'll be
>safer & a properly designed shunt ckt will allow you to test the pyro
>channels without an ignitor attached.

Shunting most e-matches won't provide much safety at all. Many common ones
(Oxral and DaveyFire N28B) take so little current to fire that the resistance
in the shunt contacts may be enough to not provide a good enough alternate
path.

I use a DPDT (double-pole, double-throw) switch in-line between the altimeter
and e-match. When open, the e-match is shorted and not connected to the
altimeter. I use a screw to keep the switch closed. To date, two of us
flying this configuration have had no failures attributable to the switch.

Glen Overby

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Phil Stein - 29 Sep 2004 17:38 GMT

>>Also, if you shunt your pyros until you are ready to launch, you'll be
>>safer & a properly designed shunt ckt will allow you to test the pyro
[quoted text clipped - 11 lines]
>
>Glen Overby

I've sent you the full contents of something I wrote on this. After
you read it, please comment.

THanks
Phil

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Arnold Roquerre - 30 Sep 2004 07:17 GMT

One can use a magnetic switch which is very easy to install and can be used
to activate at liftoff is desired.

>>Also, if you shunt your pyros until you are ready to launch, you'll be
>>safer & a properly designed shunt ckt will allow you to test the pyro
[quoted text clipped - 14 lines]
>
> Glen Overby

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J.A. Michel - 26 Sep 2004 22:11 GMT

Most altimeters have continuity checking built in, and beep out the status
of the pryo outs constantly while in liftoff wait mode. Check your ematches
for resistance with a VOM. Make sure they are within mfgr's spec. Make
sure not to leave too much bare wire from the match leads hanging out of the
pyro terminals. This might cause a short circuit and give you a false
continuity reading. Use a new battery for each flight, and check it for
voltage and amperage before flight. That's what I do, and it works for
me.....

Adding some type of plug between the altimeter and ematch like you suggest
just adds another possible mode of failure, IMO.

Signature

Joe Michel
NAR 82797 L2
http://home.alltel.net/jm44316/

> does anybody use any form of "continuty" checking within their altimeter
> circuits to make sure it is "on" "ARMED", that checks the ejection charge
[quoted text clipped - 9 lines]
>
> shockie B)

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Mark - 27 Sep 2004 03:40 GMT

Good info...

The Gwiz will show you the pyro battery voltage, the resistance of each pyro
(in Ohms), and the voltage of the Computer battery. Very handy... helped at
the last launch when we had to change an ematch because the Gwiz showed over
a 80 ohms.

And ALWAYS use a seperate battery for your pyro charges... don't use
anything that requires a single battery for 'decision making' AND pyro
ignition.

... and, as you say... Keep it simple!!!

> Most altimeters have continuity checking built in, and beep out the status
> of the pryo outs constantly while in liftoff wait mode. Check your ematches
[quoted text clipped - 22 lines]
> >
> > shockie B)

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Model Forum / General / Rockets / September 2004

altimeter arming ?