ISO of plot of Schurter (110/220) rotary switch failing.

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jahall4

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PerfectFlite as you may know is warning about the use of the popular "110/220 rotary switches". I assume they are referring to the Schurter switches. Does anyone have a plot they could post of a flight where the Schurter was used and suspected of malfunctioning?

Thanks
 
No plot. However, I will say that mine get flaky after awhile. And it's a PITA to replace them once soldered in. I'll be going a different direction in the future. However, I have never had one fail during flight. The one on my Scorpion currently needs to be tweaked to get the connection (like fine tuning a radio, if you know what I mean); but once it connects, it stays connected.
 
The data sheets for Schurter rotary switches indicate that they are designed for a very low number of operations compared to a high quality slide switch. Orders of magnitude difference.
 
The data sheets for Schurter rotary switches indicate that they are designed for a very low number of operations compared to a high quality slide switch. Orders of magnitude difference.

Well, there you have it. Are key switches more reliable?
 
The data sheets for Schurter rotary switches indicate that they are designed for a very low number of operations compared to a high quality slide switch. Orders of magnitude difference.

Yes, manufacturer rates them for 300 cycles.
Say you play with it for 50 cycles, that still leaves 250 cycles or 125 flights before the manufacturer's recommendation runs out, and manufacturers typically rate their product guarantees on the conservative side . I know some have, but not many people get 125 flights out of most of their rockets.
 
Yes, manufacturer rates them for 300 cycles.
Say you play with it for 50 cycles, that still leaves 250 cycles or 125 flights before the manufacturer's recommendation runs out, and manufacturers typically rate their product guarantees on the conservative side . I know some have, but not many people get 125 flights out of most of their rockets.
I think your analysis leaves out the following:
1. Most people don’t dedicate one set of electronics to each rocket. Whenever they move their electronics from one rocket to another they check the wiring by powering up and down. Then, whenever they prep their rocket they check to make sure their battery is ready, that’s another cycle. Some cycle the switch to check continuity of their electric matches. In short, every time something changes they cycle the switch.
2. That manufacture’s rating is for 300 unloaded cycles. These switches are intended for use in power supply applications to switch input voltage BEFORE plugging in the power cord (how often do you change this switch on your desktop computer). In our applications they are actually being used to open and close under a small load and, perhaps more importantly, under a DC load, which is harder on a switch, especially if the load includes a reactive device such as the capacitors needed for our avionics.
3. The data sheet (https://us.schurter.com/bundles/snceschurter/epim/_ProdPool_/newDS/en/typ_SWA1__Frontpl_.pdf) doesn’t specify what that number (300) actually means, but it’s probably a statistical mean, possibly meaning that for every switch that surpassed 300, one failed early on.
Those are my reasons for not using them. I have no problem with people who use them. Sometimes I just over analyze.
 
I had one fail before it flew when I accidentally turned it too far. It may have been user-error, but I'm not typically heavy-handed and it broke with very little force.


Sent from my iPhone using Rocketry Forum
 
This Schurter rotary switch failure discussion has been ongoing, and from what I have read the failure has generally been attributed to the design, but not always. At the very least from an anecdotal perspective it appears to me that the design is suspect and that there are potentially better options. So why are people still considering using them?

That being said what other switches would be considered comparable in how they are wired and operate? The first one that comes to mind is a simple screw switch. I have read discussions on failures where screw switches were used, however it was unknown if this was due to a design issue or a user issue where they did not screw them down sufficiently.

My experience has mostly been with magnetic switches which I have about 25 of them with no issues or failures. However I am starting to use the screw switches so I would be interested in hearing about experiences with a screw switch.
 
I had issues where the slot for the screwdriver to turn it gets sloppy. Also when the sled pushed the switch tightly against the airframe it did not want to turn. These are both my errors. I do not move the ebays around, so the number of cycles is not as important for me.
 
Mechanical failure seems to occur sooner than any kind of conductive failure. They are flimsy. One good crank with a screwdriver could shatter one on a cold day. But they have a very low aerodynamic profile, which is desirable over a key switch.
 
I started out using the snap action switches with my L1 av-bay. I moved to screw switches for my L2 rockets. I'm back to the snap action switches on my L3.

I've never had a problem with either type.

The screw switches I made myself with #6 brass screws, nuts and pieces of double sided circuit board.

The snap action switches I rig similar to the directions Perfectflite has. I always put the wire contacts forward so the g-forces pull the switch to its normal non-activated position. I figured that was the best way to keep the N.C. contacts closed. I use #2-56 machine screws to attach the switch to the board and JB Weld to attach the brass tube for the pin onto the board. This has worked fine for flights to just over 80G (I1299N-P in a ~3 lb rocket)

Here's the switch on my L1 cert rocket. It's the first snap action switch I used. It's the one that worked fine for 80G. I did reattach the brass tube with JB Weld after this pic was taken.

E Bay battery and switch.jpg
 
The data sheets for Schurter rotary switches indicate that they are designed for a very low number of operations compared to a high quality slide switch. Orders of magnitude difference.

What type of slide switches are you referring to?
 
I have tried a few things, and looked at many more. I keep going back to snap-acting switches (aka microswitches).

AltsCompleted.JPG

Also, consider which direction boost and ejection forces act on the lever arm. I usually put my switches across the flight path direction to minimise the amount of jounce on the switch arm.
 
Eggfinder wifi switch is great but it needs a bigger battery to keep it powered up. Mechanical switches use no standby current :) Both are appropriate in different situations and according to personal preferences.
 
I've used Schurter switches on a lot of rockets. I've never had one fail in flight but I have had to replace two of them. One got flaky and one completely stopped making contact. I'm looking for a good alternative and just yesterday ordered several Missleworks screw switches to try.
 
Slide switches are fine as long as they are protected like being inside of the E-bay.

I have personally seen several cases where an externally mounted slide switch was turned off after the Drogue deployment from the harness catching it during descent.
 
Slide switches are fine as long as they are protected like being inside of the E-bay.

I have personally seen several cases where an externally mounted slide switch was turned off after the Drogue deployment from the harness catching it during descent.

I agree; although I haven’t seen that (the switch I linked has a very small handle) that’s a valid concern. Mounting the slide switch inside the ebay so the handle is inset into the switch band would address that.
 
I agree; although I haven’t seen that (the switch I linked has a very small handle) that’s a valid concern. Mounting the slide switch inside the ebay so the handle is inset into the switch band would address that.

We always have to consider what could happen as opposed to what normally happens.
 
Edit: looks like I'm not the only one using them.

If anyone wants a bulletproof switch, these are the ones to get.
Designed for combat robot fighting, they have rock solid contact & mounts made of delrin.
Use them on all my extreme stuff. They are not cheap, but quality never is.

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

Screen Shot 2018-01-26 at 2.38.53 PM.png 20160809_113156.jpg


I still use good old twist and tape for everyday sport flying. Nothing I know of is as reliable as this method. Period.


Steve...I posted them couple years ago in my Sparrow-Arcus build, after researching switches.
 
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Edit: looks like I'm not the only one using them.

If anyone wants a bulletproof switch, these are the ones to get.
Designed for combat robot fighting, they have rock solid contact & mounts made of delrin.
Use them on all my extreme stuff. They are not cheap, but quality never is.

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

View attachment 337091 View attachment 337092


I still use good old twist and tape for everyday sport flying. Nothing I know of is as reliable as this method. Period.


Steve...I posted them couple years ago in my Sparrow-Arcus build, after researching switches.

That’s where I saw them! Thanks!
 
I recently picked up a few Binder Design screw switches and am really impressed with how rock-solid they are.

He fabricates them himself and has used them in some of the most extreme flights imaginable.

IMG_3934.jpg

In this bay for my Bigger Daddy I potted the switch in a piece of CPVC as a standoff.

IMG_3931.jpg

IMG_3922.jpg


Sent from my iPhone using Rocketry Forum
 
Edit: looks like I'm not the only one using them.

If anyone wants a bulletproof switch, these are the ones to get.
Designed for combat robot fighting, they have rock solid contact & mounts made of delrin.
Use them on all my extreme stuff. They are not cheap, but quality never is.

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

View attachment 337091 View attachment 337092


I still use good old twist and tape for everyday sport flying. Nothing I know of is as reliable as this method. Period.


Steve...I posted them couple years ago in my Sparrow-Arcus build, after researching switches.

I just used two of these on a rocket that will maiden tomorrow. They're very robust, and make clean "on" contact. The Binder switches look pretty cool, too.
 
I think I'm going to go with a micro switch and pull pin. This switch is rated at 200,000 electrical cycles. Not that I'll ever cycle it anywhere near that much, but it tells me that it's a quality switch.

https://www.digikey.com/product-det...UuphSBBJi4UzalunAC8bOCLo8FaUlvvQaAiTdEALw_wcB

You might want to consider this one. It's basically the same switch without the roller on the end of the arm. Since the arm is pretty much free/loose when the pin is pulled, having less weight on the end that can impart movement is a good thing in my opinion. A strong jolt is less likely to affect the light bare arm then the one with the relatively heavy roller.
 
You might want to consider this one. It's basically the same switch without the roller on the end of the arm. Since the arm is pretty much free/loose when the pin is pulled, having less weight on the end that can impart movement is a good thing in my opinion. A strong jolt is less likely to affect the light bare arm then the one with the relatively heavy roller.

I find the roller unnecessary, and a bad idea for the same reasons.
 
You might want to consider this one. It's basically the same switch without the roller on the end of the arm. Since the arm is pretty much free/loose when the pin is pulled, having less weight on the end that can impart movement is a good thing in my opinion. A strong jolt is less likely to affect the light bare arm then the one with the relatively heavy roller.

I actually removed the arm altogether from the switch I used in Milestone.

https://www.rocketryforum.com/showthread.php?44764-Mile-High-build-thread&p=440867#post440867
 
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