Switch Testing

[Grog6]

Something to avoid when soldering switches,don't solder the contact while it's closed. I've seen the contact pressure move the terminal just enough to not work reliably.

 

[eriggins56]

John Great information thanks so much for sharing this with all of us.

 

[cwbullet]

I did have a conversation with a combat robot guru on the Fingertech switches. He offered me tips on the switch.

1. The battery needs to be attached to the pole on the screw side. Some else said this also, but he echoed it.
2. Sand both poles lightly.
3. Clean with alcohol to remove finger grease.
4. Use a Rosin or flux.

 

[jbr]

I use a lot of this type switch and never remove the screw. Any concern it can close during transportation can be easily mitigated. It is discussed in this thread.

https://www.rocketryforum.com/threa...-switch-safety-fyi-alert.169701/#post-2210075
BTW...thanks for your work John.

these look to be similar to missileworks screw switches
I have found that the screw is slightly loose in the nut and giving it crimp to slightly damage the threads makes it tight and so it will not vibrate loose

 

[Titan II]

these look to be similar to missileworks screw switches
I have found that the screw is slightly loose in the nut and giving it crimp to slightly damage the threads makes it tight and so it will not vibrate loose

Correct. I do that on all of mine.

https://www.rocketryforum.com/threads/missileworks-screw-switch-how-to-keep-tight.140376/

 

[rharshberger]

Correct. I do that on all of mine.

Same here, it keeps it from backing all the way out without effort, and once its backed out against the "staked" aka squished portion the screw wont screw back in again on its own under vibration.

 

[JohnCoker]

I appreciate the testing. I'm not sure why time to turn on and noise while turning on are important in our application. We turn electronics or initiator circuits on, once, and time on should be irrelevant unless it is in minutes. Could you elaborate on why you feel they are important?

I would be concerned with noise and bouncing in all cases: when off, turning on, when on, and turning off. If the electronics being used is immune to say 1s of noise or bounce, then all tested switches would pass.

Since the physics of the Fingertech is similar to the Featherweight switch, if the behavior in turn on and noise is significantly different, I'd suspect the test setup.

Maybe. However, they are not the same. The Featherweight switch is rigid (PCB-based) while the Fingertech has a flexible Nylon body.

I would think that for our application, vibration and shock should be paramount. If a switch starts generating noise or bounce when it is supposed to be connected, that is a show stopper. That is why I think the Schurter and Featherweight belong at the bottom of the list.

The rating is indeed subjective. I could certainly change my mind if we learn more about the sensitivity of common electronics.

 

[Titan II]

For those that use them, Shurter switches are essentially DPST and it is logical to wire them as such. It is is discussed here:

https://www.rocketryforum.com/threads/schurter-switches-for-flight-computers.159545/

 

[Adrian A]

Both actually. Here's my "0" test (all switches off) at 500Hz. Note that purple is #5 (the Featherweight screw switch).

View attachment 585136

Here's my "5" test (only Featherweight on) at 500Hz. Note that blue is the Shurter.

View attachment 585137

If anyone is interested, I can send the data files. They're saved in TDMS format, which is consumable by many programs. (I used "DAQami", which comes from the same company that made the sampler.

It's good to see that you tested in both states. The possibility for vibration to make the screw turn when it's in the off state to intermittently turn it on is surprising. I and others have seen this before, like the thread that @Titan II pointed out, so I recommend that the screw be removed if the switch needs to be off in a vibration environment. But the lack of a solid "on" under vibration in the on state is very surprising; I haven't seen that in any of my launch data continuity voltage readings before. Do you recall how tightly you screwed it down?

 

[cerving]

I have seen "open" screw switches vibrate intermittently closed in transit. It depends on how long the screw is, and how tight it is. Some of those screw switches have very short screws... it doesn't take much. If your altimeter self-arms when power is applied, that can be a bad thing... one more reason to leave out the BP until you get to the range.

 

[mbeels]

I tend to agree, except I travel with loaded charges in rockets in the bed of my pick up. They are all screw switches, but we'll see if that ever causes an issue. I suspect not, but who knows../

I have seen "open" screw switches vibrate intermittently closed in transit. It depends on how long the screw is, and how tight it is. Some of those screw switches have very short screws... it doesn't take much.

That happened to me once. I had my rocket in the trunk of my car with charges loaded. The altimeter was on a screw switch with the screw backed out. I was driving through a bumpy gravel parking lot when I suddenly heard the sound of my altimeter arming.

Now I remove the screws completely.

 

[Highpowerrocketyahoo]

Shurter switch sitting there holding a beer wearing shades. Lol

 

[pbahorich]

Turn on time for a screw actuated switch like Featherweight or Fingertech should be a function of screw pitch and how fast the screw is tightened.
Regarding noise, contamination in the contact area could affect this. If it is inherent to the switch itself (and this is a big if) it could be that the screw turning on nylon generates static charge which is being picked up as noise in the testing.
I've had Featherweight style screw switches vibrate from open to close during the drive to the range. This is unacceptable in my view. The Fingertech switches are self-locking in the nylon and won't change position under normal gravel road vibration.

 

[JohnCoker]

But the lack of a solid "on" under vibration in the on state is very surprising; I haven't seen that in any of my launch data continuity voltage readings before. Do you recall how tightly you screwed it down?

I used only finger strength (not making a fist); I tightened it until it was firm and no farther. Sorry, I know that's not very precise.
Note that I was using a full-sized electrician style #1 Phillips screwdriver.

Also the only vibration that affected any of the switches was at 500Hz, which I doubt would have any effect. (It was the highest I went, since I was sampling at 1KHz.)

 

[TRWXXA]

Interesting data. What brand of phono jack is that? I used phono jacks for switches back in the last century, but was told they were the worst. It seemed to perform pretty well here.

 

[JohnCoker]

Interesting data. What brand of phono jack is that? I used phono jacks for switches back in the last century, but was told they were the worst. It seemed to perform pretty well here.

I don't know the brand; I probably bought it from Mouser or maybe even Radio Shack (long ago). I also was surprised it performed as well as it did. That bent metal spring works well!

A key takeaway for me (which sounds obvious in hindsight) is that traditional switches just work. I'm not sure the "special rocketry" switches really add anything.

I personally like the Featherweight and Fingertech switches and will continue to use them, but I can't recommend anything with caveats or that requires special procedures. People here interested in this topic can be trusted to read up and take extra care, but I think it would be irresponsible to recommend something that doesn't work without non-obvious fiddling.

 

[mtnmanak]

Would love to see these screw switches added to a future test:

http://binderdesign.com/store/switches.html
I use them in all my rockets 6" diameter and up and they have performed wonderfully. I have had a couple cases where I needed longer wires on the switches and Mike at Binder Design has made them for me and had them shipped out the next day.

Admittedly, these would not be great options for smaller diameter rockets.

 

[TRWXXA]

A key takeaway for me (which sounds obvious in hindsight) is that traditional switches just work. I'm not sure the "special rocketry" switches really add ananything.

That's the takeaway I get too. And certainly, with the brownout protection being more common than it was 25 years ago, it would take a switch that can be jarred to *off*, and stay there, to be a fail.

 

[cwbullet]

That's the takeaway I get too. And certainly, with the brownout protection being more common than it was 25 years ago, it would take a switch that can be jarred to *off*, and stay there, to be a fail.

That is a fair assessment.

 

[Steve Shannon]

A key takeaway for me (which sounds obvious in hindsight) is that traditional switches just work. I'm not sure the "special rocketry" switches really add anything.

For years I have been recommending the NKK miniature slide switches. They’re rated for 50 gees of shock and vibration in six degrees of freedom.
Unfortunately they’re no longer available with solder lugs on their terminals, but Cherry Switch makes some that are nearly identical. I think the Cherry Switch is what PML used to sell that they said were 50 gee rated.

 

[Glasspack]

Thanks John

Always enjoy your videos and knowledge......
I have switched over to a Featherweight Screw switch after the NEW Schurter Power Select Switch failed before I even finished building the model.
Hopefully this Featherweight will prove great !! May try some of the tricks talked about, making the screw tighter to turn thus avoiding
vibration problems.

 

[cwbullet]

Thanks John

Always enjoy your videos and knowledge......
I have switched over to a Featherweight Screw switch after the NEW Schurter Power Select Switch failed before I even finished building the model.
Hopefully this Featherweight will prove great !! May try some of the tricks talked about, making the screw tighter to turn thus avoiding
vibration problems.

View attachment 585641View attachment 585642

That switch does not look like a Schurter Power Select Switch. Did you scratch off or sand off the logo? Schurter's have a logo on the top.

 

[jahall4]

That switch does not look like a Schurter Power Select Switch. Did you scratch off or sand off the logo? Schurter's have a logo on the top.
View attachment 585668

Probably marked over it with a sharpie like I have done on mine. If you magnify his photo you can see the markings.

 

[Worsaer]

I’ve switched to using the FingerTech switches, and have had great success. My only caveat is that don’t like the supplied aluminum hex screw - I tend to bugger them up if the allen drive isn‘t well aligned. To fix this I always replace the aluminum screw with stainless screws (from McMaster).


A box of 100 will last a lifetime…
https://www.mcmaster.com/92196A108/

 

[jahall4]

I’ve switched to using the FingerTech switches, and have had great success. My only caveat is that don’t like the supplied aluminum hex screw - I tend to bugger them up if the allen drive isn‘t well aligned. To fix this I always replace the aluminum screw with stainless screws (from McMaster).

Would you be kind enough to share the McMaster part number?

 

[tsmith1315]

My only caveat is that don’t like the supplied aluminum hex screw

An aluminum (oxide) screw with copper terminals? I wonder if a brass or stainless screw would perform any differently in the vibration tests.

 

[cwbullet]

Would you be kind enough to share the McMaster part number?

That would be helpful.

 

[cwbullet]

Probably marked over it with a sharpie like I have done on mine. If you magnify his photo you can see the markings.

View attachment 585674

Thanks. I have always had good success with these switches. I reared use them today because I have found cheaper options.

 

[Swany]

Good stuff, John. I would be curious if the results of the vibration test would be different if you repeated the testing with different orientations of the switches. The test setup in the video looks like the vibration table is vibrating up and down, which would be the most stressing case for the featherweight switch since the vibration is occurring exactly perpendicular to the switch contact area. I don’t think this is necessarily true for the other switches.

 

[Reinhard]

For years I have been recommending the NKK miniature slide switches. They’re rated for 50 gees of shock and vibration in six degrees of freedom.
Unfortunately they’re no longer available with solder lugs on their terminals, but Cherry Switch makes some that are nearly identical. I think the Cherry Switch is what PML used to sell that they said were 50 gee rated.

The MS series switches from NKK in the panel mount variant (with solder lugs) are available from a couple of vendors
https://octopart.com/search?q=MS12AFW01 (SPDT)
https://octopart.com/search?q=MS22AFW01 (DPDT)

Reinhard