In the attached schematic, what prevents the MOSFET from turning off during pauses in the audio, such as between tracks?
Thanks.
Thanks.
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So, that is the purpose of C4 in this circuit?The charge on the capacitor will hold it on longer if you increase the value.
Thanks.Yes, it is. The diode D1 makes sure that C4 can only discharge slowly through the 10M resistor R11. So once turned on, it will stay on until the voltage on C4 falls thru the threshold area to off.
Don't press the button!Do you think there a way to prevent that?
Thanks again. I changed C4 back to 100 μF, and R9 to 1k. These changes reduced the duration and the magnitude of the voltage spike, but did not eliminate it.Don't press the button!
Returning C4 to a larger value might help, as might increasing the value of R9 a bit, for instance to 1K. Both of these would act to prevent a brief spike from actually raising the gate voltage, the voltage across C4.
Thanks for your help. A 1000 μF cap makes the release time way too long. I ordered some breakout boards for the SOIC8 LMC7215, and will build that circuit to try.It would probably be better to "integrate" the input signal than try to integrate the op-amp output, although I suppose either approach gives the same end result. Maybe you just need 1000µF.
I need an opamp with a low current drain because it will be on all the time monitoring the output from the MP3 player.Hi tracecom,
I like the LMC7215 circuit. I would use that, rather than the 1458-based design. You don't need to use that device though, especially if you're running it at 5V instead of 3V (which is fine).
I would like to see your circuit. Thanks.I have done this using an limiting OP amp, detector and timing 'hang' for gaps in the audio. I shall sketch out a circuit and post if you like.
It is doing A1 service as a 'silence' detector in a community radio station.
by Jake Hertz
by Jake Hertz
by Aaron Carman
by Jake Hertz