Electronic Switches for the inexperienced

[Art Upton]

That's good to know about. What kind of failure was it? Was it a permanent failure (the switch came apart) or was is just a temporary failure while the rocket was accelerating?

BTW, the POPO switch is a double pole switch. I wired both poles in parallel thinking that if one pole temporarily failed due to thrust that the other might still be okay. No failures that I can pin on the switch yet...

It's a challenge trying to find a reliable switch that can withstand high current and high thrust.

Jim

Hi Jim, the switch failed open at apogee. After recovery in a nice soft field in a flat spin we examined the switch. It no longer mechanically operated.

I used the black 110/220 round style switches and twist the wires after that. However after many years I have a total of three 110/220 switches out of nine broke on the ground in testing operations. They just spin rather then switch anymore. Two of those seemed to last about 3 years in normal operations. One however got some rough treatment and only lasted about a year.

So last year I replaced them and put in new rockets the N3 screw in switch.

Screw in Switch Link

I've flown two of those in Miss Chievious to 998mph and 21,500 MSL. One other rocket had this switch to 43gs. I've only used them for about 15 months so I do not have an estimate on how long they will last like I do the 110/220 switch.

 

[falingtrea]

As far as current is concerned, most switches are rated at 250VAC or higher for the current. At a lower voltage the max current is usually higher.

 

[FredA]

"As far as current is concerned, most switches are rated at 250VAC or higher for the current. At a lower voltage the max current is usually higher."

Not really true.
The current carrying capacity and the voltage withstand are two different animals. The current is [usually] limited by tempreture rise due to IR heating. The voltage limit is derived from the break spacing and other insulation parameters. Also, the AC current rating is usually way higher than the DC current....there is a reason we use AC for distribution.

But again - we don't really stress the switch with 9V alkaline powered circuits - almost anything will do - select on the quality of the positive contact make - beyond that, pick what fits and functions for your application.

 

[oliver1111]

I am also planning on using 2 separate NoMatch systems for ejection.
...
Should I have an on/off switch for the NoMatches?
Shaken, not stirred… sometimes with a lemon peel
007

I personally don't think you need a separate switch for NoMatch, but read the "Reliability" section of my website.

 

[fastfreddie]

Ok, I forgot to mention that I really do not understand too much of this electronic stuff, so please me gentle with me. Let me know if I got this right.


Would I use 2 of them? One to power up both Altimeters and then one to arm all charges?


007

You would want to use one switch for each of the altimeters and one for each of the charges. For a dual altimeter setup that would be a total of 6 switches. I personally don't put shunts or switches on my charges as it just adds another failure point. The smartest way is to put the switch in the positive wire between the battery and the altimeter and just put a jumper wire in the "switch" terminal on the altimeter. This insures that there is NO power present on the alt board until it's armed on the pad. No power on the alt means no chance of setting the charges off inadvertently, and no need for shunts.