What sort of switch do I need for this electronics project?

February 24, 2020 4:57 PM

I am in the process of designing/building a simple DIY music controller and am trying to buy some switches from mouser or digikey but am not sure which "switch function" is the one I am looking for. I'm not quite sure how to interpret the On-(On), On-On, On-(Off), etc..., values.

My design has three switches:
A: SPDT toggle
B: SPDT momentary/pushbutton
C: SP3T slide

A should be your "normal" switch where it is creating a path between the center terminal and either the left or right terminal depending on its state. I think this is "ON - ON"?

B should function similarly to A except that it should should reset itself to its default state when not being pressed (like a keyboard key). I think this is "ON - (ON)"?

C is used to switch between 2 paths, with the center position being off. I'm not sure what switch function this would be, or if I even need SP3T switch for this. Are there SPDT switches with an "off" in the middle?

Could somebody in the know please explain which types of switches/switch functions I need?

posted by Television Name to Technology (5 answers total)

You have this right for A and B.

For C, you could use an SP3T and leave one pin unused, but there are also SPDT switches with a central off position. That combination would be called "On-Off-On".

This is quite a good overview of common switch types and the terminology around them.
posted by automatronic at 5:06 PM on February 24, 2020

I agree with you for A. For B I think it will say On-Mom. For C you could use either a slide switch or a selector switch (On-Off-On or Mom-Off-Mom depending if you want it to latch into place).

Also I work in the east bay (Emeryville) and have a bunch of panel mount digikey switches that I bought to see how they feel to use - if you want to drop by sometime and mash some buttons, private message me. Mine are all momentary switches of various types except the one I messed up ordering, so they might only cover use B directly
posted by aubilenon at 5:09 PM on February 24, 2020

One thing to keep in mind is single throw momentary pushbuttons are "normally on" or "normally off". Some are double throw that can function either way. Just make sure you get one that will function as you expect.
posted by 2N2222 at 6:19 PM on February 24, 2020

I don't know if it matters in my case. The button and toggle are for muting and unmuting a signal. My plan is to wire the toggle and button terminals together so the the button can act as a momentary mute/unmute depending on the toggle's state.
posted by Television Name at 7:52 PM on February 24, 2020

I don't know your circuit, but "normally on" or "normally off" momentary pushbutton may matter. If it's directly opening and closing the audio path, a normally-on will cut(mute) the audio signal when pressed. If the audio is being shorted to ground, a normally-off switch will short the signal to ground (mute) when pressed. If the momentary switch is being used to control a VCA or digital control/microprocessor, it really depends on the design/programming.
posted by 2N2222 at 5:12 AM on February 25, 2020