I soldered the Schmitt trigger onto a BoB then bodged it onto the HMI board using 0.3mm bodge wire. The controller is an ESP32 and I was having trouble with the hardware interrupts because the RC debounce I was using was too slow. The Schmitt trigger gives me a nice, square signal which the controller interprets properly. The chip cost me a couple of bucks from Digikey.
Here’s the best RC trace I could get.
and here’s the trace with the Schmitt trigger (same scope settings.)
I included a short, technical explanation because this is a soldering group and not an electronics group. I was posting the picture of the chip soldered onto the BoB and the BoB bodged onto the HMI board because that was soldering.
But…
Switches are mechanical devices. When you press the switch it may appear to you that it’s a clean, immediate on or off, but in electrical terms switches are dirty. Most don’t cleanly make or break the connection. Switch bounce can look like this:
Image borrowed from https://www.circuitbasics.com/switch-debouncing/ which provides a good explanation of what I’m doing. In fact they use a 74HC14 which is related to the chip that I use.
Controller chips often read the switch bounce as separate presses which can mess up your program. Many people use software to debounce their switches by incorporating delays in the programs to make sure that the switch has been switched.
You can also use a resistor and a capacitor to smooth out the transition from high to low which gives you a debounced signal in the form of a curve rather than a sharp transition. That looks like this:
Depending on your controller chip this may solve the problem. When you’re using a really fast controller or when your controller is tristate the transition through the zone where the controller goes from thinking that a signal is high to thinking that a signal is low the controller can sometimes go back and forth a few times which is the same thing as bounce.
The contrller that I’m using, the ESP-32-WROOM-32, is one such fast tri-state controller. Using the best combination of resistor and capacitor that I could find I was getting three or four triggers on the transition from high to low and one or two on the transition from low to high. That is less than ideal.
So, I decided to use a Schmitt trigger. (A commenter linked to this excellent Wikipedia article.)
The Schmitt trigger give a much squarer, much more tri-state controller friendly debounced signal like this:
This is not strictly soldering related but I thought it might help. I’m happy to answer questions about what I did or the materials that I used if there are any.
Your dead bug looks a bit more dead cephalopod to me.
It looks like a centipede but there is all that web.
I was wondering when the r/VXJunkies community would start moving over to Lemmy
I should take anther run at the explanation?
