Wiring Ejection Charges

ROL "infocentral" is a good place to start (http://www.rocketryonline.com /), but the site just changed (I won't say upgraded) a few days back, and I've
yet to find infocentral!
The basics are (were) there

so
a
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wrote:

http://info-central.org/infocentral.shtml
--
Darren J Longhorn http://www.geocities.com/darrenlonghorn /
NSRG #005 http://www.northstarrocketry.org.uk /
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Infocentral:
http://www.info-central.org/infocentral.shtml
Another good source, go to the Perfict Flite site and download the manual for the MAWD:
http://www.perfectflite.com/Download.html
AZWoody wrote:

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AZWoody wrote:

Top of the home page, there's a link to Info Central.
-Kevin
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Kimball,
Have you checked out Mark Canepa's Modern High Power Rocketry 2? I'll bring a copy to the launch this AM and you can check it out.
James

so
a
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No I have not checked out Marks Modern High Power Rocketry 2. I did not know about it. But thanks to you I can now. I hope you have a good launch this am. I won't be there. I am a church goer so thats where I'll be sitting. Have fun though. See you at the next saturday launch.
Thanks Kimball
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Read the manual that comes with whatever electronic device you buy. You might also read the manuals of the devices you are interested in before you buy one so you have an idea of how the various devices work.
Ask people at the launch. Most people are happy to answer questions and give advice.
Phil
On Sun, 04 Jun 2006 04:37:19 GMT, snipped-for-privacy@pacbell.net wrote:

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snipped-for-privacy@junglevision.com wrote:

Please think very hard before you use a key switch. They require keys to operate, right? What happens if the rocket lands far enough away (or is lost) and someone else finds it before you get to it with the key?
What happens if there is a live charge left in the rocket?
Use something that is easily operated with common tools (a screwdriver, for example). Label it, so that e.g., if your rocket is hanging from a powerline, the lineman can disarm it before fooling with it.
Also, make sure the switch you're using is both rated for the current it will be drawing, and mechanically able to withstand the vibration it will encounter. A surplus mil std microswitch, securely mounted, and operated by a bolt inserted into the airframe, can work really well.

Standard practice is to switch the positive wire, isn't it?
--tc
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yes it seems to be.
but electrons flow from negative to positive, so if you switch the negative, you shut off the electrons before they leave the battery ?
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wrote:

Ted is correct. Switching the positive is standard in electronics. Electrons don't flow unless there is something (like the positive lead) to attract them.
Phil
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Humm..
I've heard removing the negative (switching it) will help black wire disease ?
CD
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snipped-for-privacy@unverified.com says...

Yeahbut...does it help with restless leg syndrome?
--
Tweak

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Tweak wrote:

Isn't that "the Jimmy legs"?
--
Mark Recktenwald
NAR 77432, L1
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snipped-for-privacy@gmail.com says...

ROTFL
He said jimmy legs.
--
Tweak

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do
purpose.
Thank you.
Adding a shunt does not prevent stupid mistakes (wrong battery polarity, etc), but adds one more possible stupid mistake.
I for one, when preping a bird with electronics, will tie yellow "caution" tape on the bird. Once the bird is on the pad, and the electronics are armed, the tape comes off. (prevents not arming the electronics)
The reason I do this, is that from the flight line, I can tell of the "proper steps" were taken.
Also, one thing that I do is to do a "test arming" of the electronics during prep. Prior to any BP being anywhere near the ematch. Worst case is the ematch might pop if theres a problem, but can be done in a way to not present a safety issue.
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Larry,
I agree with AZWoody. Adding a switch or shunt to the ematch adds another failure point to the system. If you want a switch, add it where it will do the most good - to power your alt off and on. A voltage selector switch from a computer power supply is my favorite switch to use for that purpose.
Thank you.
Adding a shunt does not prevent stupid mistakes (wrong battery polarity, etc), but adds one more possible stupid mistake.
I for one, when preping a bird with electronics, will tie yellow "caution" tape on the bird. Once the bird is on the pad, and the electronics are armed, the tape comes off. (prevents not arming the electronics)
The reason I do this, is that from the flight line, I can tell of the "proper steps" were taken.
Also, one thing that I do is to do a "test arming" of the electronics during prep. Prior to any BP being anywhere near the ematch. Worst case is the ematch might pop if theres a problem, but can be done in a way to not present a safety issue.
Gentlemen I agree with both of you. I use an on/off switch only to power up the electronics. I have even gone so far as to eliminate the terminal board on the electronics bay bulkheads. I run the ematch wires directly to the boards, no junctions. Where the ematch wires penetrate the bulkheads I seal them using a fender washer with a soft rubber washer under it. This has worked so far and I have not noticed any evidence of ejection gas in the ebay.
--
William Richardson ENC USNR Ret.
TRA 8703 L2
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I've done it successfully both ways. I have an alt bay with ematch terminals on the outside of the bulkheads - which works fine. I have two others that I just drilled a hole in the bulkhead to pass the ematch leads and hook them directly to the alt's pyro outs. I use blue wax (it's a mushy wax like modeling clay) to seal the ematch holes. I prefer passing the match leads directly thru the bulkhead - seems less complicated and more reliable. It's too easy to make silly mistakes, so the simpler the better!
--
Joe Michel
NAR 82797 L2
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wrote:

The altimeter beeps will indicate if one of them opens up. When you unshunt, listen for any changes in the tones coming from the altimeter.
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A couple years ago I was prepping for a flight. I had recently added a switch inside my ebay to turn on or off the Perfectflight MAWD altimeter. I was testing the altimeter power switch. The events went like so...
I turned the switch on. (Insert screw). The Altimeter started beeping away indicating all good and there was continuity to the ematches. Then I turned the altimeter back off. (Remove screw). The altimeter didn't turn off. I used the wrong screw and the switch got mashed and therefore was jammed in the on position. Now I have a rocket that has charges armed and ready to go off. Well I have a couple other friends and flyers next to me as I'm doing this and after trying to bump the switch back to the off position I finally decide the only way I can get the power off now is to disassemble the rockets electronics bay and remove the power source or power lead from the battery. As I go to pull apart the rocket I unknowingly put my hand over the altimeter vent. I must say I and my friends are all really glad I do a lot of ground testing and fine tune my ejection charges rather than using the blow it out or blow it up idea because as I closed my hand over the port, POP. The drogue charge goes off. The bottom of the 12 pound rocket goes slamming into the ground at my feet. Now I'm a little dazed as to why that just happened but I figured it out as I was setting the rest of the rocket down and I take my hand off the vent hole. POP! the main charge goes off this time. The nose cone narrowly misses my friend!
I learned several things that day.
#1 Screw switches should be removed to arm not installed to arm. #2 All ematches should be shorted until the rocket is on the pad and ready for the igniter. #3 Never cover a barometric vent hole #4 Keep the pointy end up
I changed my set-up after that incident. Now I have a new set up using switches that will short up to 4 ematches individually. As long as the screws are through the airframe holding down the switch the altimeter will not get continuity and the ematches are shorted so they are safe from static and RF energy. I also use a separate connection or switch to arm the electronics.
Layne Rossi

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Why were you arming the charges before the rocket was on the pad ?
If you wanted to check ebay setup with the ematches, do that before you you ever add BP.
Once you ad BP, don't turn on or arm anything until you get the rocket mounted on the pad.

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