Ideas for small hard-to-accidentally-hit reset button?

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joem
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Ideas for small hard-to-accidentally-hit reset button?

Post by joem » Wed Sep 16, 2020 4:38 pm

I'm designing a eurorack module that's powered by an Arduino and is being designed so that users can make their own code for it. (I know, I know... these already exist. But I'm making one for video synth purposes, so some of the electronics necessarily needs to be different than existing ones.) While designing some of the built-in factory modes that'll go with it, I've encountered a few situations where it locks up or crashes. Ideally, I'd just program it so that never happens (and I'm doing my best to make sure the factory modes won't!) but a reset switch will still be pretty handy, I think, especially if users write less-than-stable code. I'd rather have it there and not get used than not have it when it's needed. I know electronically how it'll work, just a NC momentary switch that the +5V to the arduino goes through.

I think ideally I'd like to make one of those resets holes like what's on a lot of routers, where you insert a paperclip into a hole to press the momentary switch. That way it's very hard/impossible to accidentally hit, and it takes up almost no front-panel space. I'm thinking I'd need a switch cap that comes to just under the front panel and has a concave top? Does that sound right? Does anyone have any experience doing this for a eurorack module? Will this be stable enough, or will it be too easy for the paperclip to slide off the switch cap and accidentally hit the pcb/parts near it? (I really wish I had an old router to take apart and look at right now!) I've started a dive into switches and caps on Mouser to see if I can even find such a switch/cap combo, but I think it's going to take me a while...

Also, if anyone has an idea for a good alternative method to make a hard-to-accidentally-hit reset button that doesn't take up a lot of front panel space, I'd love to know. Are there any digital modules out there that have such a feature?

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by Altitude909 » Wed Sep 16, 2020 5:05 pm

Just a 6mm tact with a long actuator that ends just below the panel will do it. Something with a low actuation force would be good

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by Synthiq » Wed Sep 16, 2020 5:52 pm

Have you considered using the watchdog timer to automatically reset the processor if the program locks up and you stop resetting the watchdog timer?

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by MikeDB » Wed Sep 16, 2020 5:54 pm

I use a similar switch with an 18mm long shaft that just comes into a hole on the front panel but doesn't protrude. You can press it with a ballpoint pen rather than searching for a paperclip, but still not able to be pressed accidently
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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by brycecake » Wed Sep 16, 2020 6:01 pm

THIS IS NOT WHAT YOU ASKED AND I'M SORRY.

May I suggest.... make the panel hole big enough to reset with a cable jack? Still too small to accidentally poke, but convenient since users will not have to keep track of a paperclip while debugging

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Thu Sep 17, 2020 9:02 am

brycecake wrote:
Wed Sep 16, 2020 6:01 pm
May I suggest.... make the panel hole big enough to reset with a cable jack? Still too small to accidentally poke, but convenient since users will not have to keep track of a paperclip while debugging
^I agree. Came here to make the same suggestion. Be sure your solution works with a 3,5mm patch plug tip and you're golden.
------
Also see that a version of my second suggestion is already here. That being you may not want to run the full DC power of an Arduino through a typical tact switch. The current isn't trivial, and DC ratings for switches are FAR,FAR less than for AC. Meaning you're setting yourself up for fused switch contacts <--at first glance without knowing details. That's service calls and support you don't really want or need.

If you're going to use a tact sw for reset, find a low amperage place to do it. Can't imagine there's not one conveniently available and designed in already on an Arduino.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by ersatzplanet » Thu Sep 17, 2020 11:38 am

Standard jack with the power running through the normalization. Plug in any patch cord breaks the connection. Mark the jack appropriately to keep accident low.
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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Thu Sep 17, 2020 12:19 pm

It's not often I find myself in disagreement with ersatzplanet.
Strongly disagree here.
OP asked for minimal panel area solution. Using a jack not only takes up a lot of panel space it also takes up even more behind the panel-on the pcb for the jack body. Also not sure how much more DC ampacity a 3,5mm jack normal has than a heavy duty tact. There's more area for sure, but since jack mfrs aren't expecting high current it might not even be enough.

Though again the break power to reset is IMO a non-starter in the first place.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by snowtires » Thu Sep 17, 2020 12:48 pm

You could do what the Mutable modules do and put small SMD package switches on the very sides of the board, so you can reach it as long as the side of the module is free. If you're dealing with coding your own module, it's probably not in a permanent position in your rack.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Thu Sep 17, 2020 12:52 pm

Another alternative to hard-to-hit is to use a looonnng press of a button and do the rest in software. Casual bumps or normal use of the button doesn't cause the reset, and you don't need any additional panel holes or components.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by joem » Thu Sep 17, 2020 3:55 pm

Wow. Lots of great ideas! Thanks everyone.

I'm going to have to think about things and try to figure out what works best. I'm especially going to investigate ways to do it without adding more hardware. I didn't think it'd be possible, but maybe it is. I haven't dove too deep into why it locks up in the first place, so I guess I need to figure that out.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by joem » Thu Sep 17, 2020 4:08 pm

KSS wrote:
Thu Sep 17, 2020 9:02 am
Also see that a version of my second suggestion is already here. That being you may not want to run the full DC power of an Arduino through a typical tact switch. The current isn't trivial, and DC ratings for switches are FAR,FAR less than for AC. Meaning you're setting yourself up for fused switch contacts <--at first glance without knowing details. That's service calls and support you don't really want or need.

If you're going to use a tact sw for reset, find a low amperage place to do it. Can't imagine there's not one conveniently available and designed in already on an Arduino.
Very good point. I completely forgot that Arduinos have a RESET pin that'll make them reset when it's grounded. :doh:

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by nigel » Thu Sep 17, 2020 6:46 pm

KSS wrote:
Thu Sep 17, 2020 12:52 pm
Another alternative to hard-to-hit is to use a looonnng press of a button and do the rest in software. Casual bumps or normal use of the button doesn't cause the reset, and you don't need any additional panel holes or components.
Good for a final product, not so useful for user-written and/or crashed code (as in the original request).
Although you could do the same thing with a small hardware delay circuit before the reset pin. (A resistor / capacitor and a schmitt inverter might be enough.)

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Thu Sep 17, 2020 7:23 pm

I'm not following your reasoning?
OP provides the code -and hardware config- to allow for the long press reset. End user decides to use it or not.

Could instead be a multi-button press, to cut down on time to activation. At the expense of being more possibly inadvertently actuated.

But it didn't seem from OP that quick or hardcore 'emergency' response was necessary. More just having *a* way to reset available.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by nigel » Thu Sep 17, 2020 10:02 pm

KSS wrote:
Thu Sep 17, 2020 7:23 pm
I'm not following your reasoning?
OP provides the code -and hardware config- to allow for the long press reset. End user decides to use it or not.
The impression I got from the OP was that they wanted a physical switch to handle situations where the code had crashed:
joem wrote:
Wed Sep 16, 2020 4:38 pm
I've encountered a few situations where it locks up or crashes. Ideally, I'd just program it so that never happens (and I'm doing my best to make sure the factory modes won't!) but a reset switch will still be pretty handy, I think, especially if users write less-than-stable code.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Fri Sep 18, 2020 5:59 am

nigel wrote:
Thu Sep 17, 2020 10:02 pm
The impression I got from the OP was that they wanted a physical switch to handle situations where the code had crashed:
Yes, that's what I understood too. A long press -or multi-press- simply takes advantage of the inevitable switches already on the module.

I'm stil not seeing the disconnect between this and what OP asked for that you're seeing?

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by nigel » Fri Sep 18, 2020 9:35 am

KSS wrote:
Fri Sep 18, 2020 5:59 am
nigel wrote:
Thu Sep 17, 2020 10:02 pm
The impression I got from the OP was that they wanted a physical switch to handle situations where the code had crashed:
Yes, that's what I understood too. A long press -or multi-press- simply takes advantage of the inevitable switches already on the module.

I'm stil not seeing the disconnect between this and what OP asked for that you're seeing?
If the software has crashed, how is it going to detect button presses?
Which is why I suggested a hardware delay of some kind connected before the reset pin.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by KSS » Fri Sep 18, 2020 10:23 am

Thank you.
My mental picture of how this module would be done included overseer functions above the user code. That was where I had the disconnect with what you were trying to say. I hadn't -cuz I wouldn't- thought of a module so barebones.

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Re: Ideas for small hard-to-accidentally-hit reset button?

Post by ersatzplanet » Fri Sep 18, 2020 10:59 am

KSS wrote:
Thu Sep 17, 2020 12:19 pm
It's not often I find myself in disagreement with ersatzplanet.
Strongly disagree here.
OP asked for minimal panel area solution. Using a jack not only takes up a lot of panel space it also takes up even more behind the panel-on the pcb for the jack body. Also not sure how much more DC ampacity a 3,5mm jack normal has than a heavy duty tact. There's more area for sure, but since jack mfrs aren't expecting high current it might not even be enough.

Though again the break power to reset is IMO a non-starter in the first place.
I agree with you. It was a worst case solution for many reasons. The power break is a pretty sledge-hammer method and spending on the jack used, both size and current ratings both factor into it.

I personally think the button behind the panel that doesn't run power, but does a soft reset, is the solution. It is by far the most used methodology out there. Why reinvent the wheel?
-James

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