ac signal supervisor

[John150]

Hi

I have an AC signal that I want to supervise.
Based on the signal I want to enable/disable an other device (+3.3VDC).
I was thinking to use an opamp but any other suggestions should be welcome.

Questions:
1. How can I convert the AC +/- 0.2V to 3.3VDC?
If the AC signal is zero or below +/-0.2V the opamp output to be zero.
If the AC signal rise above +/-0.2V the opamp output to switch to 3.3VDC? I do not want to have negative values for -0.2VAC.

2. For the opam I'm looking to have a delay on falling back to zero. How can I do that?
In other words if the AC signal is zero or below +/-0.2V the output to be zero. If the AC swing above the +/-0.2V the output of the opamp to stay at 3.3VDC and if the AC signal falls back to zero the opamp's output to remain hi for 5-10 seconds?

Regards,
J.

 

[Audioguru]

What is "AC +/- 0.2V"? Is it 0.4V peak-to-peak?

A full-wave precision rectifier circuit can have its output filtered then drive a comparator circuit. The opamps can use a single positive supply voltage and their bias voltage can be half the supply voltage instead of ground.