Leaf Switches Flaky: What am I missing?

[acarle]

Greetings!

I’ve been working on a custom virtual pin controller for my own use. It is built around an ESP32 microcontroller, with my own electronics and software managing the tilt detection, plunger, and buttons.

Everything is working great except for my flipper buttons. They are standard cabinet buttons hitting Williams/Bally-style single contact leaf switches. The type that looks like this:

I have a proper leaf switch adjustment tool for manipulating the switch. But no matter what tweaks I make, I can’t seem to get consistent results. Every adjustment I make seems to end up with the switch either stuck on constantly or unable to trigger with the flipper button. Sometimes I will get it just right, but 10 minutes of actual use will get it stuck in one state or the other. It’s driving me mad.

My wiring is trivial, but I’m wondering if there’s something fundamental that I’m missing here. (My background is more on the microcontrollers side and less on the pinball electronics side.) I have a 3.3 V power supply connected to one of the leads of the switch. The other is connected to a GPIO on the ESP32, configured to use the ESP32’s internal pull-down resistor to keep the pin low when the switch is open. I have no other passives in the circuit.

When the switch is misbehaving, I can see that the issue is electrical, not software. With my multimeter hooked up where the ESP32 would normally sit, I can see that I’m not getting any voltage through when it is stuck low. Often I can even manually push the two halves of the switch together with my finger and still I don’t get a consistent signal.

I guess my questions basically boil down to this:

1. Is there some reason that 3.3 V would be insufficient here? I know that in a real table these switches are controlling much higher voltages, but I didn’t see any obvious reason it shouldn’t work fine at the ESP32’s native 3.3 V.
2. Is there some finicky adjustment to the switch that I’m not making but should be? Perhaps something about the angle/rotation of the contacts or depth or… something?
3. Are there supposed to be other passive components in the loop here? I was imagining that the leaf switch would work like any other digital switch, but perhaps there’s something I’m entirely missing here.

Any help would be greatly appreciated!

– Andy

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[acarle]

I’m reporting back, just in case anyone stumbles into this topic in the future.

I was able to fix my flaky leaf switches and take them from ~25% reliable to 100% reliable. All it took was two steps:

1. I roughed up the contacts of the leaf switch a tiny bit with an emery board.
2. I cleaned the contacts with a little 99% IPA on a q-tip.

I don’t know if the important action here was more about cleaning the surfaces with the abrasive and the IPA (they were unused, but had been sitting on the shelf for a few years) or more about roughing the surface to improve contact. But either way, it made a huge difference. Everything is A+ now.

– Andy

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[Thalamus]

Good to hear that you resolved your issue. After you telling the solution, I guess it makes sense. Reason for not coming up with such suggestion myself is that I haven’t cleaned mine and they work perfectly.

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