WAV trigger hookup buttons and 3.5mm inputs question

Sensors Sound & Audio
1

Hi team,

I am trying to make the WAV trigger into a little drum machine, that can use both momentary switches and/or 3.5mm audio inputs (which will send 5v pulses from a step sequencer through an audio cable) to activate the triggers. I want to do this while leaving the trigger setting as the default “Contact Closure.” Basically trying to make something like in this video:

https://youtu.be/HJ4qzxSFKHk

I’ve wired up the switches and they work fine. For the 3.5mm cables, I am trying to use a 2N2222 transistor as a switch, so I have wired it up like this:

DrumMachine_bb.jpg
DrumMachine_bb.jpg1893×1818 377 KB

However, when I send a 50ms 5v pulse thru the base of the transistor from an arduino, it just activates the trigger nonstop, repeating the sound quickly. (I get the same result when I touch the base with my finger)

I also want to have an LED light up whenever the trigger is activated.

Any ideas on how I can wire this up?Maybe some kind of capacitor or resistor on the emitter? Am I on the right track?

Thanks!

2

UPDATE: If I do the same thing (send a pulse from the Arduino to the base of the transistor) with the Arduino on a power supply ie not USB connected to the computer, I just get random trigger activations, not the continuous re-triggering. WHen I put my finger on the transistor base, though, it still does that, which I guess is me conducting EM energy into it.

3

You’re probably going to want to add a 330 to 1K ohm resistor in series between your signal source and the base of your transistor to limit current on the base.

I’d also suggest a 10K to 1M ohm resistor between the base and ground to keep that pin from floating. What’s likely happening is the base is picking up stray static or RFI and turning on. A 10K to 1M ohm resistor should keep the base low until your external circuit pulls it high.