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servo control

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New Member
I have 2 electret mics, 1 left, 1 right, these are fed through comparators.

I want to control a servo in such a way that the servo is at centre position and if more sound enters the left mic, servo moves left.

After a small delay, servo centres.

The same would apply to the right mic.

I have tried using a 16F628A pic but I am not getting the results.

I thought some sort of bridge circuit would do..

Can anyone help, please.


A comparator is about useless for that, you need an integrator. Even then though with echo it won't work quiet right. You'd need to use three mics and triangulate the volume source. Four if you want to sense it in 3D. Three sensors will only sense accuratly on the plane the sensors are in. It's a lot more complex than you might think.
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Active Member
your making a robot that pretends to follow a conversation between two people arent you?


New Member
Hi, Sceadwian, Sorry, I am using LM358 Opamps, not comparators.

I did not get to bed till 2:15am, and my brain hurts.

I got it to work on one channel but when I added the right hand channel to the Pic and programmed it, one channel remained "ON".

Like I said, I was up till late trying to work out the problem.

I thought the best way would be a servo in balance using some sort of bridge......


New Member
Hi, Triode, No, I just want it to look alive to sound.

Many years ago a guy rigged up a head on a snake like body which moved towards the sound source. The body was a flexible tube with three steel cables running up the middle.

It was installed in a museum.

The cables moved the head forward , left or right.

I had a video of the beast which showed it lunging towards the people

I have lost the video and circuitry.

I just want my project to follow the sound source.


Active Member
Can you be more exact about your problem here please.

You say that you got one channel to work, what exactly does it do when it works? and what is "on", the servo? the input?


New Member
Thanks for your reply.

I have abandonded the project in favour of my pir setup which works perfectly.

The electret mics were too sensitive to spurious noise.
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