Altimeter Switches

[Theory]

Looking for a pair of rotary or screw switches for my next project. My last build used the 6-32 PCB switch that missileworks sells. I have it mounted to the sled and access it through one of the static ports in the switch band of the AV bay. Works well.

The next build will use an RRC2+ and RRC3 and for full redundancy I would like to use two switches. I could use the same system as my last build, but getting the two stitches to line up correctly will be challenging. I like the idea of surface mounted switches, but I have read poor reviews on the rotary switches sold by doghouse. The ones that missileworks sells look to be the same.

So what say you? What sort of switch is your favorite?

And no, I'm not a twist and tape guy.

 

[OverTheTop]

And no, I'm not a twist and tape guy.

Excellent!

I will let others recommend rotary switches. I am a pull-pin addict.

 

[RainierWolfcastle]

https://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch

I wish I could remember who first recommended them to me, because they are awesome.

 

[GaryT]

I preferer these heavy duty push button switches, been using them for 10 years and never had one fail. I line up and drill 2, 3/32 holes and use a 3/32 T-Handle allen wrench to turn them on and off.

 

[DAllen]

The only thing I don't like about a lot of these screw type switches is it requires a tool to arm/disarm or you set a switch inside the e-bay and need something pokey to operate them. I'd really like to see a switch that can be operated with my clumsy fingers from the outside of the rocket so I don't have to remember to bring a tool with me during recovery so I can turn off the beeping alts. Knowing my luck, if I set a switch inside my ebay like GaryT does I'd manage to dislodge something important off the altimeter or something else equally idiotic.

So that Fingertech Robotics switch - I wonder if I could swap out that allen screw with a thumb screw of some sort...hmmmm

 

[cwbullet]

https://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch

I wish I could remember who first recommended them to me, because they are awesome.

This is what I would suggest.

 

[Buckeye]

The switch thread is the new glue thread.

 

[mpitfield]

I use these regularly.

https://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch

I wish I could remember who first recommended them to me, because they are awesome.

 

[Theory]

The switch thread is the new glue thread.

yes, but that is only because we all know that 6209 is the best, and when its not one should use rocketpoxy that has been allowed to rest for a period of time or slow or mid cure US composites provided that it is mixed with some or none of the fillers that they provide in a ratio left to ones discretion based on the application in question, but this is only when the application renders BSI insufficient based on value, strength, availability, color, smell or any combination thereof.

back to switches!

 

[Eric]

I have used the screw switches and the rotary switches. I like them both, but lately I really like the pull pin switches. The pull of one pin can activate one, two or three switches. Lab Rat Rocketry has a pretty nice setup.

 

[Mugs914]

I have been interested in trying pull-pin switches, but don't they require that the alts are powered up while you assemble the av bay? Once everything is buttoned up the pin is inserted and everything switched off again, right?

Not a big deal in most cases, I reckon. I have one project that this would be perfect for, but at least one set of charges must be in place before the av bay is inserted in the tube, and I'm really not interested in assembling the thing with live charges and hot altimeters!

Will definitely give 'em a go on other projects though...

 

[FredA]

Eric - nice, but ONLY you can disarm the rocket and that's if you didn't lose the pin ==> not so nice.

Switchcraft 4PDT slides work great.
For a 2-charge rocket, it provides a pair of redundant contacts for power plus the disconnect-and-shunt capability for the two charges.
All in ONE switch.

Just glue down the tabs where the metal bends over the back and they are bulletproof. Have flown 100's without incident.

 

[Zeus-cat]

I really like the magnetic switches from Featherweight.

https://www.featherweightaltimeters.com/store/p4/Magnetic_Switch.html

 

[rocketgeek101]

I really like the magnetic switches from Featherweight.

https://www.featherweightaltimeters.com/store/p4/Magnetic_Switch.html

I've been considering using these in my next build. I plan to have redundant DD. How does one deal with having two switches in close proximity? Wouldn't you run the risk of accidentally disarming one, while activating the other by waving the magnet around?

 

[Bat-mite]

I used the Doghouse style 110/220 rotary switches exclusively until I noticed a trend of the plastic breaking and introducing a lot of wiggle in the "on" position. I switched to these. I also used a magnetic switch once. Found it frustrating to try to find the switch while on the pad.

The ones linked above lock the key in the switch in the off position. Attach a "remove before flight" banner, and then if you or the LCO sees the banner hanging from the switch, you know you forgot to arm the altimeter.

 

[Mugs914]

I imagine if you mounted them on opposite sides of the bay it would be okay. The website said activation within one inch with the magnet. Would need to be careful about waving the magnet around none the less...

Interesting thread! Much more so than the glue thread...

 

[Cl(VII)]

I have been interested in trying pull-pin switches, but don't they require that the alts are powered up while you assemble the av bay? Once everything is buttoned up the pin is inserted and everything switched off again, right?

Not a big deal in most cases, I reckon. I have one project that this would be perfect for, but at least one set of charges must be in place before the av bay is inserted in the tube, and I'm really not interested in assembling the thing with live charges and hot altimeters!

Will definitely give 'em a go on other projects though...

You are absolutely correct. The pull pin switches are best used in a "traditional bay" setup with a switch band. That allows you to assemble the bay, insert the pin to power everything off (I put a piece of tape over the end of the pin to make sure I don't snag it on something when working), and then load the charges. You should never assemble a bay with the charges loaded and altimeters active.

Right tool for the job, and these pull pin switches are not the right tool for a fully removable bay that doesn't have a switch band. For the record, I rely on the magnetic switches from Featherweight in those cases.

I have used the screw switches and the rotary switches. I like them both, but lately I really like the pull pin switches. The pull of one pin can activate one, two or three switches. Lab Rat Rocketry has a pretty nice setup.View attachment 395309

Thanks for the endorsement. This post also reminds me I need to get the triple switch on the website.

 

[Theory]

Gonna have to noodle the idea of the pull pin. I like the idea of having both switches on one "pin," and I be building the traditional fully removable bay with a switch band.

Bat-mite, those key switches look legit, however, with an external diameter of 22mm, I dont think they will fit well on a 4" airframe.

 

[boatgeek]

I'm a fan of the Missileworks screws switches, largely because they worked after some disasters with the 110/220 switches. I've found that if you use a slightly smaller screwdriver (not one with replaceable bits) and you set up the switches right next to each other, you can turn both switches through a 1/2" diameter hole. This was on 3" and 4" rockets with the AV sled pretty much in the middle of the rocket. I like sled-mounted switches because you don't need any external wiring besides the wires to the charges.

 

[Zeus-cat]

I've been considering using these in my next build. I plan to have redundant DD. How does one deal with having two switches in close proximity? Wouldn't you run the risk of accidentally disarming one, while activating the other by waving the magnet around?

I find the switches to be a little finicky regarding the magnetic field so unless they are right next to each other you won't trigger them both. I recommend that you mark on the airframe EXACTLY where you need to swipe the magnet to turn the switch on or off.

 

[mpitfield]

You want to place them at opposite ends of the AV bay, not the other side. They can be opposite ends and the other side, but it is much more important that they are at either end of the bay. Obviously there are a lot of assumptions in that comment, so it is just a general rule.

I've been considering using these in my next build. I plan to have redundant DD. How does one deal with having two switches in close proximity? Wouldn't you run the risk of accidentally disarming one, while activating the other by waving the magnet around?

 

[Bat-mite]

Bat-mite, those key switches look legit, however, with an external diameter of 22mm, I dont think they will fit well on a 4" airframe.

True dat. You may be able to find half-inchers on Digikey, etc.

 

[Nytrunner]

Oh yes, dual magnetic switches. To watch a student team waving their magnet back and forth alternately turning one on and the other off simultaneously is only amusing for a couple minutes. Then it starts to impact schedule

 

[micro]

I've never had trouble with the schurter rotary switches. Maybe people are overheating them when soldering. Maybe they got some Chinese knock-offs from eBay. They are rated for 300 cycles, maybe replace them after 100 flights? If I don't have a screwdriver handy I use the end of my house key that's always in my pocket.

 

[heada]

3PDT slide switch. Switches power and both charges at the same time. I mount them horizontally so that they're not easily influenced by g-forces. Anyone can switch them on/off as needed, no tools or lining up anything internal. I wouldn't use them on a MD rocket or greater than mach 1.something. At $2 each, they're cheaper than a 9v battery and those are pretty much single use now.

https://www.digikey.com/product-detail/en/cw-industries/GF-161-3011/SW121-ND/9613

 

[Bat-mite]

I've never had trouble with the schurter rotary switches. Maybe people are overheating them when soldering. Maybe they got some Chinese knock-offs from eBay. They are rated for 300 cycles, maybe replace them after 100 flights? If I don't have a screwdriver handy I use the end of my house key that's always in my pocket.

I find that it is easy to overcrank them and break them. They work fine if you are gentle with them, but I am not very sensitive and tend to turn them too hard. So I need metal.

 

[cerving]

OK, I'll throw my hat in the ring... Eggtimer WiFi Switches. Remote operation, no tools (other than your phone), no holes, they power-up OFF, and you get battery voltage and igniter continuity too (if you hook it up).

FYI, If you use Eggtimer Quantum or Proton altimeters, you don't need a switch at all, because a switch for the deployment power is built into the deployment circuitry and won't come on until you're safely in flight. Tripoli recognizes this and allows them to be used for TRA L3 certs without a separate switch, subject to the approval of your TAP.

 

[boatgeek]

I've never had trouble with the schurter rotary switches. Maybe people are overheating them when soldering. Maybe they got some Chinese knock-offs from eBay. They are rated for 300 cycles, maybe replace them after 100 flights? If I don't have a screwdriver handy I use the end of my house key that's always in my pocket.

My trouble with the Schurters was really about installation. I had them hard mounted to the switch band and then wired to the sled. I had a hell of a time getting the sled in and out without breaking off the switch leads. The one I have mounted to the sled works better, but then has no real advantages over a sled-mounted screw switch.

I also like the WiFi switches/altimeters.

 

[Bat-mite]

My trouble with the Schurters was really about installation. I had them hard mounted to the switch band and then wired to the sled. I had a hell of a time getting the sled in and out without breaking off the switch leads. The one I have mounted to the sled works better, but then has no real advantages over a sled-mounted screw switch.

I also like the WiFi switches/altimeters.

That's a good point about any rotary switch. The depth has to be accounted for/mitigated.

 

[FMarvinS]

I've had success with the pull-pin switches. If you have access to a 3D printer, you can print an enclosure for multiple switches inexpensively to work with one pull-pin (see below).

The only caveats are: 1. the recurrent use of a metal pin can enlarge the channel that enables the pin to close the switch arms and make switch closure not totally reliable.
2. The pin or rod can "slide" out of the channel with movement or vibration during transportation and cause unexpected premature altimeter activation.

To solve caveat 1, I have placed metal tubes in the pin channel to minimize widening of its diameter and this appears to work well.
To solve caveat 2. Some tape the pin or rod in place to prevent movement or "sliding" out of position until just before launch. Recently, I've placed a nut at the far end of pin channel (within the printed PETG switch enclosure) and simply screw the threaded end of the pin (rod) in place to prevent sliding during set up and transportation. Just prior to launch, the rod is simply unscrewed and maintained within the channel.

Fred, L2
ICBM, S.C.
KG4YGP