ebay switch: no moving parts

[Sully]

I think this is a new product from Apogee. It was highlighted in the latest email newsletter and I haven't seen it before. Given all the debates about various switches and their reliability during boost, I thought this was an interesting alternative. Small (weighs 7g) and costs $20.

Here's the link to Apogee's product page.

They show it with push-button switches that basically you have to hold for 4 seconds to turn the switch on or off. But there is also the option of using screws through the airframe (or nosecone) that you can manually bridge with a wire for 4 seconds, which does the same thing.

Has anyone used this or a similar switch? On the one hand, it looks like the wire/screw method would have no chance of opening the circuit even under high G's (site claims it's been tested up to 300Gs). I think that even if the solder broke and the wire came loose from the screw, the switch would still remain in the same state, on or off. But as we know, anything we add is a potential failure point, and this is a pretty complex switch to replace a simple screw switch or twisting wires together.

There's something about only having exposed screw heads that I like though: easy to arm and disarm and also has a cool factor.

Again from Apogee's site (btw I am not a shill for Apogee, just have been a customer in the past, and like their selection and service but don't always like their prices):

 

[dixontj93060]

I don't understand the "no moving parts" comment as you still have switches to operate.

 

[CarVac]

I'm not sure whether it's better to use this or a Featherweight magnetic switch for crazy high acceleration flights. On my minimum-mass I1299 flight to 220 G, I used a Featherweight screw switch tightened down REALLY tightly. Something happened and I was unable to find it...

In any case, whether I trust it or not depends on whether it retains its state after battery disconnection. The magnetic switches are slightly iffy because they require a flip-flop to fall into a given state.

EDIT: I read the site, and in the case of a disconnected battery it ALWAYS comes up off. That's a no-go for high-G flights.

EDIT: I reread the site and it says it keeps the state for short power losses.

 

[Sully]

Yes, it can be used with push-button switches that have to be held down for 4 seconds. One button for on, one for off. That would have moving parts.

OR you can have screws that are simply conductors that you can bridge with a wire for 4 seconds. That is the configuration without the moving parts. Kind of like a touchscreen keyboard vs. a keyboard with buttons on your phone. Both have switches, but the touchscreen does not have a mechanical switch component like the switches underneath each key.

 

[troj]

I think the point is that the actual power switch has no moving parts, and thus isn't susceptible to switch bounce in flight

The arm/disarm triggers (switches) are separate and could be removed before flight

 

[CarVac]

I somehow imagine that it needs serious epoxy potting for a really high g flight. Did they do a sustained 300 g or did they drop it on a sled with an accel that registered 300 g, I wonder.

 

[kruland]

It probably uses some kind of electronic latch which is put into the closed state by holding the button. Once the button is released, the latch is still closed and will be until the other button is held for 4 seconds. The only real concern is if the "off" button could be held closed for 4 seconds because of various forces on the rocket during boost. It would certainly be more reliable if you had to say, hold a screwdriver to short two header pins to turn it off.

 

[troj]

It probably uses some kind of electronic latch which is put into the closed state by holding the button. Once the button is released, the latch is still closed and will be until the other button is held for 4 seconds. The only real concern is if the "off" button could be held closed for 4 seconds because of various forces on the rocket during boost. It would certainly be more reliable if you had to say, hold a screwdriver to short two header pins to turn it off.

Just leave the "off" leads hanging out of a hole, and taped to the side of the airframe. If you need to turn it off, strip the leads, and hold them together for the required amount of time. No switch to bounce, no leads to accidentally short.

-Kevin

 

[Rocketjunkie]

Just leave the "off" leads hanging out of a hole, and taped to the side of the airframe. If you need to turn it off, strip the leads, and hold them together for the required amount of time. No switch to bounce, no leads to accidentally short.

-Kevin

If you're going to do that, might as well use twist and tape down. Nothing to buy.

 

[CarVac]

If you're going to do that, might as well use twist and tape down. Nothing to buy.

Except that the wires can be ultra-tiny, since they don't actually carry any significant current.

 

[Sully]

If you're going to do that, might as well use twist and tape down. Nothing to buy.

I still prefer twist-n-tape: nice and simple. But having three screw heads and bridging them with a screwdriver or wire has a bit more cool factor.

 

[dlb]

If you're going to do that, might as well use twist and tape down. Nothing to buy.

Hey hey I like twist and tape, be nice.