I am building a beacon transmitter for a high altitude balloon. The beacon needs to be turned-on with a small, light, rugged switch just prior to launch. The battery will likely be a Lithium like one of these.

The switch must have a positive ON indication (visual check of the physical position of the switch handle) or other indication that consumes very little power. This is so it can be checked visually just prior to launch. Launch is in direct sunlight, so I want to avoid an LED indicator...

The switch must be mechanically guarded so it cannot be accidently turned off by being snagged or dragged (the ground, bushes, trees, parachute shrouds, etc) by being recessed and/or by using a positive locking switch with a Lift-over-center handle.

Current/Voltage is 6Vdv at ~100mA

Temperature goes to -50 deg C

I've thought about a NC magnetic reed switches (where the magnet holds the switch open and the magnet is removed just prior to flight)

It could be done by not installing the battery until just prior to flight.

It could be done with an insulating mylar tab that is pulled out from between the battery contact just prior to flight.

Anybody have any other ideas?

 

one that has worked before is a standard 1/8 inch phone jack, the kind with the speaker switch built in, put a plug in it and the switch is open, pull it out and the swtch closes an 1/8 inch wood or plastic stick works too, thats whats used on the radio sond baloon packages. very light, and dosnt stick out.

 

my local ham radio club launched several balloons a few years ago, we used a styrofoam minnow bucket and sent up a simplex repeater, the last thing before taping the lid on was to drop in a couple of plastic bag type hand warmers. kept the electronics inside working at somewhere around 100,000 ft (estimated from the range of people using the repeater, amarillo tx to oshkosh wi.) another thing that makes it easier to find on the ground is to attach a sonalert with a 9 volt battery on the outside, the battery freezes up at high altitudes, then thaws and beeps when it comes down.

 

What about a tiny slide switch, recessed so it cannot be moved without a pen or small screwdriver etc?

Even a tiny DIPswitch? They usually have gold plated contacts, and some are already recessed to avoid accidental switch movement;

 

The part with the least likely failure more is the one you didn't use.

Therefor I'd just go with battery insertion as the switch, or the mylar tab removal.

 

Advantage of the mylar tab is that you can attach a length of brightly colored tape or ribbon to it so it is very obvious that the tab is in place. This also works for the phone jack idea suggested by alfacliff

 

Advantage of the mylar tab is that you can attach a length of brightly colored tape or ribbon to it so it is very obvious that the tab is in place. This also works for the phone jack idea suggested by alfacliff

Traditionally the "tape" is red in color marked in white letters "REMOVE BEFORE FLIGHT".

(image to follow)