# Altimeter switch style

### Help Support The Rocketry Forum:

#### RocketTree

##### Active Member
I'm new to rocket electronics and have been searching for altimeter power switches for a while. Can't seem to locate the mini slotted rotation switches anywhere.
These are the only options I could find... Anybody able to point me in the right direction?

#### Attachments

• 276.3 KB Views: 1

#### Titan II

##### Well-Known Member
"Can't seem to locate the mini slotted rotation switches anywhere."

These?

#### heada

##### Well-Known Member
Stay away from anything momentary or spring loaded. I use DPDT slide switches or the rotary ones linked by John above (schurter switches)

#### RocketTree

##### Active Member
Great! Just learned of a couple new styles there.

I am located in Canada, so ordering one switch comes to almost $30 USD from any of those sites (due to shipping). Would have to be from an electronics shop (mouser, etc), amazon, ebay. Also, on a similar subject, would you recommend starting with shear screws or styrene rod to retain the rocket sections before deployment? Thanks for the suggestions. #### jderimig ##### Sponsor TRF Sponsor ^ Fingertek, support your fellow Canadians. #### new2hpr ##### Well-Known Member Mouser has the Shurter rotary switches: 693-0033.4501, 693-0033.4503, 693-0033.4504. Not sure the difference between them, but take a look. #### cwbullet ##### Obsessed with Rocketry Staff member Administrator TRF Lifetime Supporter Global Mod ^ Fingertek, support your fellow Canadians. You know how I feel about those darn Canadians......... Love em just as if they were family. Plus it is a lot better than supporting China. #### Wizard ##### Well-Known Member Great! Just learned of a couple new styles there. I am located in Canada, so ordering one switch comes to almost$30 USD from any of those sites (due to shipping). Would have to be from an electronics shop (mouser, etc), amazon, ebay.

Also, on a similar subject, would you recommend starting with shear screws or styrene rod to retain the rocket sections before deployment?

Thanks for the suggestions.
I use nylon screws, either 2-56 or 4-40, depending on section mass. I always tap the holes as well, even cardboard. Use a little CA (thin) to strengthen the cardboard. I have 20+ flights on some carboard rockets with no shear pin hole distortion. By tapping the holes you can get a snugger fit, which will help with shear behavior. You want fast, brittle fracture, not deformation/stretching of the shear pin. Loose fits can lead to more viscoelastic deformation. I also strongly suggest using 3 to keep the sections straight and prevent off-axis twisting.

#### heada

##### Well-Known Member
LOC sells a kit with M2 or M3 or M4 sheer screws. They include the screws and a tap. I haven't used the kit but seems like a good set up. I use 2-56 1/2" nylon screws I got from McMaster-Carr close to 10 years ago. A bag of 250 was just a few dollars and I already had a 2-56 tap. If you're ordering nylon screws from McMaster, get some shim stock too and line the sheer pin joint with shim stock and help cut the nylon screw.

#### Handeman

##### Well-Known Member
TRF Supporter
Of course, I'm partial to the pull-pin style, but these aren't for every person or every application.

https://www.labratrocketry.com/product-page/pull-pin-switch-kit
I would be more inclined if they made the pull pin where you could hang a "Remove Before Flight" flag on it. What's the point of the pull pin if you can't have the flag?

I use cotter keys because they are easy to put the flag on.

#### Cl(VII)

##### Chris Bender, Lab Rat
TRF Sponsor
I would be more inclined if they made the pull pin where you could hang a "Remove Before Flight" flag on it. What's the point of the pull pin if you can't have the flag?

I use cotter keys because they are easy to put the flag on.
View attachment 417701
I can't tell if this is a setup or not, but either way, I'll take it.

Comes in a triple version too, but posting that pick seemed redundantly redundant.

#### Greg Furtman

##### Well-Known Member
TRF Supporter
For my next build I'm using these.

Along with this.

#### Dudeman247.

##### Member
Does anybody have reliability concerns with the PCB screw switches? Vibration/backing out while in flight? I'm thinking about using them but I have those concerns.

#### Handeman

##### Well-Known Member
TRF Supporter
For my next build I'm using these.

Along with this.
I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.
I won't have a use for the surface mount since I always mount my screw switches on the sled. I use a pull pin through the switch band and a screw switch in the lower part of the bay that will be hidden inside the booster BT during flight. The screw switches gives me a way to turn everything off while loading charges, but without the pull pins and flags dangling and getting in the way or getting damaged.

You just need to make sure you turn them on after you put the pull pins in. You tend to remember after you've gotten a large rocket on the pad, pull the pull pin and nothing happens.

#### dlb

##### Sky Pyrate...
Two thumbs up for fingertech robotics switches. Battlebot recommended and you never take more abuse than a battlebot. I never seen a failure.

#### Attachments

• 148.9 KB Views: 16

#### Greg Furtman

##### Well-Known Member
TRF Supporter
I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.
I won't have a use for the surface mount since I always mount my screw switches on the sled. I use a pull pin through the switch band and a screw switch in the lower part of the bay that will be hidden inside the booster BT during flight. The screw switches gives me a way to turn everything off while loading charges, but without the pull pins and flags dangling and getting in the way or getting damaged.

You just need to make sure you turn them on after you put the pull pins in. You tend to remember after you've gotten a large rocket on the pad, pull the pull pin and nothing happens.
@Handeman I'll be mounting the switch inside my AV bay on the outside wall where the tube band is. The mount comes with different curvatures and gets glued to the AV tube.

#### Handeman

##### Well-Known Member
TRF Supporter
@Handeman I'll be mounting the switch inside my AV bay on the outside wall where the tube band is. The mount comes with different curvatures and gets glued to the AV tube.
@Greg Furtman

That sounds good. I've done it similar on some of mine.

Like I said, now I use the screw switch in series with the pull pin and mount it to the sled. I just find it easier to pull the sled out without the screw switches being separate like the pyro channel terminals on the end caps. Since I turn the screw switches on after inserting the pull pins, during prep, I don't need to access them at the pad so sled mount works for me.

#### rharshberger

##### Well-Known Member
I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.
I won't have a use for the surface mount since I always mount my screw switches on the sled. I use a pull pin through the switch band and a screw switch in the lower part of the bay that will be hidden inside the booster BT during flight. The screw switches gives me a way to turn everything off while loading charges, but without the pull pins and flags dangling and getting in the way or getting damaged.

You just need to make sure you turn them on after you put the pull pins in. You tend to remember after you've gotten a large rocket on the pad, pull the pull pin and nothing happens.
Those are the same switchs Missleworks sells, I love em. I have made a 3D printed screwdriver guide that mounts over them that keeps the screw from being able to unscrew far enough to fall out accidentally and once backed out to the off position friction captures the screw to stop it accidentally vibrating into the on position.

#### OverTheTop

##### Well-Known Member
I use snap action microswitches and pull pins. The pins are actually old allen tools and the hole in the handle takes the RBF tags nicely.

#### Locksmith

##### Well-Known Member
TRF Supporter
I only use fingertech switches, although I think pull pins are cool can’t wrap my head around how they couldn’t be turned off we g forces. fingertech switches are all but bullet proof.

#### Reinhard

##### Well-Known Member
I only use fingertech switches, although I think pull pins are cool can’t wrap my head around how they couldn’t be turned off we g forces. fingertech switches are all but bullet proof.
I don't remember ever hearing about somebody complaining that pull pins failed, so I'm confident that their reliability is at least decent.

There are a few simple rules that I observe, and I haven't had any problems yet.
• Use good quality switches. E.g. Omron SS (standard sized) or Omron D2F (micro sized). If multiple version are available, don't use "low force" versions.
• Use switches without a lever. A plunger only version works well with a little chamfer on the pin. For example D2F are specified up to 30g (which is likely conservative) but only without the lever or the lever firmly depressed (which is not the case, after the pin was removed).
• Orient the switches horizontal, so that accelerations from motor thrust and ejection charges are perpendicular to the plunger direction. See picture from @OverTheTop in post #22 for an example.

A minor drawback of RBF pins is that you usually need to remove them to assemble the e-bay. In this case, you need to be able to disconnect either the battery or the charges until the pin is reinserted to avoid handling live charges during prep.

Reinhard

#### Handeman

##### Well-Known Member
TRF Supporter
I don't remember ever hearing about somebody complaining that pull pins failed, so I'm confident that their reliability is at least decent.

A minor drawback of RBF pins is that you usually need to remove them to assemble the e-bay. In this case, you need to be able to disconnect either the battery or the charges until the pin is reinserted to avoid handling live charges during prep.

Reinhard
This is why I use the screw switches in series with the pull pin switches. I can turn everything off with the screw switches when the pins are removed. Once all the charges are done and the pins go back in, you can turn on the screw switches just before final assembly and never have to handle live charges.

What I like about the pull pin switch is that it's only operated when on the ground. The switch is mounted with the switch part down. Thrust then works to increase the force of the internal spring keeping the switch more firmly in the Normally On position.

#### amiliv

##### Well-Known Member
All of those switches are just standard electronics components. I think DigiKey has Canadian webstore (digikey.ca). Probably others. No need to pay through the nose for cross border shipping. And there's likely other sources of generic electronics components in Canada.

#### Fuddrucker

##### Well-Known Member
I have been using these key switches for years and have never had any issues. Sometimes you can find them from other sellers on sale for 0.99 ea. Just solder on the wires and add a little shrink wrap is desired and done.

...Fudd

#### HVArcas

##### Well-Known Member
Does anybody have reliability concerns with the PCB screw switches? Vibration/backing out while in flight? I'm thinking about using them but I have those concerns.
LOL

(sorry, I realize that is not a helpful reply by itself. but after you get your hands on some and use them in real situations, you will LOL at the concern as well )

#### rharshberger

##### Well-Known Member
LOL

(sorry, I realize that is not a helpful reply by itself. but after you get your hands on some and use them in real situations, you will LOL at the concern as well )
+1, I have been using the Missleworks type pcb screw switches and other than one where the screw fell out when I unscrewed it too far, no other issues. The fix for the one was just "staking" the end of the screw so it could not back out all the way. On my own 3d printed bays I have a screwdriver guide that fits over the switch so a screwdriver hits the screw first time every time, it also has a tapered lower section that would also keep the screw from possibly backing out and when the switch is open it keeps it from vibrating closed.

#### HVArcas

##### Well-Known Member
+1, I have been using the Missleworks type pcb screw switches and other than one where the screw fell out when I unscrewed it too far, no other issues. The fix for the one was just "staking" the end of the screw so it could not back out all the way. On my own 3d printed bays I have a screwdriver guide that fits over the switch so a screwdriver hits the screw first time every time, it also has a tapered lower section that would also keep the screw from possibly backing out and when the switch is open it keeps it from vibrating closed.
Like you I have made my own backings (or simply been slow / careful / hopeful) but for those who have not seen there are now APE shrouds (available from chris or with the switches themselves) that will block screws from being unscrewed too far

Not perfect for every application but definitely a good option

2