Simple Proper Switches

So, physics can be a problem with fast electronics. When you flip a light switch, your eyes see it go from dark to light. But the metal contacts are more like a rubber ball, bouncing up and down with peaks and valleys until it settles. The switch bounces between states.

You can compensate for that bounce with a capacitor. It'll smooth those violent peaks and valleys into a graceful hill. But what we really want for interrupts on a microcontroller is a clearly defined sharp square transition, the kind you get from an inverter.

Put it all together...

Another small product I made for myself to ease the pain of breadboarding, this board combines two 5mm metal switches with all the supporting hardware for each switch: two resistors, a capacitor, and a Schmitt Trigger inverter.

Using it...

Pretty much, you plug in ground and power and then run 1 and 2 to your LEDs or whatever. On an Arduino connect switch pins 1 and 2 to pins D2 and D3. Push the button, get a clean interrupt. I test them with my Common Cathode breakout board: When I push the button, the green light turns red until I release the button. Simple enough. (I also have a demo Arduino sketch to serial-print detected interrupts that I should put on GitHub, message me if you want it published.)

I don't understand the problem this solves.

Besides the human interface problem of breadboard chaos and those stupid resistors I always bend and the small plastic switches that pop out all the time, there's actual science too. Check out Derek Molloy's video on Debouncing an SPST.

I really need 1.8V or 3.3V...

Yeah, so, the PCB says "5V only" but that's basically a mistake from before I switched parts. I only test with 5V, but the Schmitt Trigger inverter is TI part SN74LVC1G14, which should be okay from 1.65V to 5.5V. Consider the "5V only" to mean "Don't plug directly in to a 9V battery."

Shipping notes

This ships assembled so I can test it out. Header pins are now sent attached unless you request otherwise, except for international orders using Cheap Shipping. If you just want parts, I have literally thousands of SMD components sitting around, so if you for example are prototyping with this board and then want some 5mm push buttons for your PCB, send me a message.

Similar solutions

If this looks interesting, check out the eeZee Switch from Bot Thoughts too or the Micro Switch from Atom Soft. Elecrab has a debounced ecSwitch with a nice layout.