3 way Switch + servo= routing audio?

Looking at my dream projects i noticed that i really need a way to route audio - with an arduino. The goal is to keep the path analog, but controlling it digitally. I had the McGuyverish idea of just connecting a small servo (controlled by arduino) to a (stereo) switch. Try to calibrate it a bit, or just test if the signal is coming through.

Although i can solder and program a little bit, im trying to keep things simple (also parts wise). Can you guys tell me if this is the way to go? or are there better ways to achieve this?

You can use a servo to operate a rotary switch. Below shows a simple setup you could try using a servo and a switch from Radio Shack.


What is the justification for using a cheap rotary switch and a servo to turn it? Especially when you can use relays. Or even better, a purpose-built A/V matrix IC the size of your little fingernail that costs less than the servo.

Well, for the "justification" I am able to provide a solution actually based on the post subject title "3 way Switch + servo= routing audio?". ;) Tough, but somebody has to do it. I've never tried relays, but from my reading mechanical relays may introduce an ugly "pop" for the listener to enjoy. I've done a good bit of small soldering and would expect the "little fingernail" IC to be a challange. Just for simple entertainment, I've switched audio/video just using transistors. If the audio is line level, a 4051 or similar chip may work.

The relay pops are sometimes caused by differing DC potentials on coupling capacitors into and out of the different audio sources. Putting some high-value pull-down resistors on the relay contacts is an accepted way of handling this.


If you need to use a rotary switch, you could just ground the common pin and use the other switch terminals on some digital input pins. Then write your sketch so that the rotary switch controls the relays.

The servo idea is fun but rotary switches often require a lot of torque to switch.

The servo idea is fun but rotary switches often require a lot of torque to switch.

What I did with my Radio Shack switch:

"SWITCH: The switch needs to be modified to remove the "click" mechanism, which is hard on the servo. Look closely at the switch and you will see a small BB held in place by a piece of spring metal. Lift the spring metal up and pop out the BB. Then carefully work on bending the spring metal up until it does not contact or catch on the bumps, and the switch turns smoothly."

i really need a way to route audio - with an arduino

The fundamental requirement of CCrooked was as above, using a servo etc would be fun and that's fair enough, but it's not the best way to do it.

As mentioned relays are the simplest and arguably the best way, special audio switching chips come equal first probably, but for a one-off home project just get a relay, write 5 lines of code and job done.

Use a latching relay and you don't even have to constantly hold the current with the Arduino pin.

wow thanks guys, i guess a relay is the way to go. The servo idea i came up with just because i used those in the past for different projects, didnt even know how a relay worked (sounded like something that would be complicated or expensive).

Just wondering, when i need to switch between 3 or 4 paths, are there cheap and simple relays to do this or does that require putting multiple in tandem or something like that?

i need to switch between 3 or 4 paths

All relays are simple and most are cheap. 2 ways can be done with a single relay, 3 ways needs 2, 4 ways needs 3 etc.