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Is there any way to get a 5V TTL signal (pulse of whatever duration, could even be a boxcar) from a button press with a very simple circuit or with some consumer device?

I need this to do some debugging, and am a bit surprised — given how ubiquitous TTL pulses are in electronics — that I can't find anything for the simplest possible instantiation of creating such a pulse. I would imagine a lot of people need such a device just to test stuff out 🤔 I have found a number of questions here (e.g. this one), but they seem to address much more specific use cases.

I guess I could just connect a few batteries in series to get to about 5V and just connect/disconnect the wires... But that would give me a lot of current as well, in addition to being pretty finicky to operate.

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  • \$\begingroup\$ Yes? A button already does this. If you connect it to 5V and a pull-down resistor, or vice versa. \$\endgroup\$
    – user253751
    Apr 24 at 18:32
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    \$\begingroup\$ well, for TTL you presumably want it connected to ground with a pull-up, because TTL likes to sink current into outputs and not source it. If you just want a 5V pulse, then either way works. \$\endgroup\$
    – user253751
    Apr 24 at 18:32
  • \$\begingroup\$ What is "a boxcar"? \$\endgroup\$
    – jonathanjo
    Apr 24 at 18:43
  • \$\begingroup\$ If looking for a consumer device, I'd probably guess that Adafruit would be the place to look. (No idea if they sell it, but I associate them as trafficking in these kinds of products since it fits their customer base well, to my mind.) They do have a blog on the topic. I used to use the 74121 and/or 74123, but those may be getting scarce. Have you looked at the 74123? \$\endgroup\$
    – periblepsis
    Apr 24 at 22:52

2 Answers 2

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Make a simple pulser with a microswitch and a flip flop to create a debounced TTL signal. Usually you can make something like this out of found parts. You'll need some clips and/or a probe to connect to the power of the circuit under test and inject the signal. enter image description here

Image source: https://www.eejournal.com/article/ultimate-guide-to-switch-debounce-part-5/

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Many people use the GPIO pins of their computer for this; if not available, then handshake lines of a USB TTL serial port might work for you.

There are a great number of such things available: enter image description here
Google search for usb ttl serial port

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