Changing from sound to voltage

[Hrthomas]

Hi
I would like to change so i dont get a sound out when an object is close but instead a relay thats active when something is close to coil, is this a big problem? What need to be changed/added to the pcb?

[waltr]

Without know circuit details:

A loud sound would have a high peak to peak amplitude. So one way would be to rectify and amplify the audio signal that then drive a transistor to switch a relay.

Also it is very possible to pick off a point before the audio that can be threshold detected to drive a transistor to switch a relay.

What gain and which transistor to use depends on which relay you use (coil Voltage and resistance along with pull-in and hold specs).

A quick look at SurfMaster schematic shows that picking off the SAT amp (U3a) would be good. This is a Voltage that drives the audio (sound) so no need to convert audio to Voltage.
Then feed this in a comparator (may need a buffer or amp) and then the the relay driver.

[Hrthomas]

Thank you very much for your reply, I will test this out

[waltr]

Ok and please do post your experiments and what you did to get this working.
Cheers

[Suvabard]

Similar experiments:

https://www.geotech1.com/forums/show...&highlight=led