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I would like to enable power to a regulator from a 1Vpp guitar pickup. Threshold can be between 0.2V and 1V. And I need it to disable after about 60 seconds of no signal from the pickups.

I'm considering using a Schmitt trigger and a RC circuit add the delay for disabling the regulator. I need to increase RC to get 60 seconds and change the schmitt trigger specs from my schematic.

Does anyone know of a better way to accomplish this?

current configuration

Update (from Andy's comment) enter image description here

physiii
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  • Are you planning to use VOL pot (for lower threshold, for instance)? Or is it always all the way up? – Rohat Kılıç Sep 29 '17 at 21:05
  • I was planning on setting the threshold using something like a voltage divider but Andy suggested a different circuit I think may work - only problem is it's a few extra components. – physiii Sep 29 '17 at 21:41
  • I asked that because the VOL pot's position (0 Ohms at max volume and 200k or 400k at nearly min) plus DC resistance of the pickup (about 10k) will be the output impedance which is quite high. So some extra precautions would be taken. Just saying. – Rohat Kılıç Sep 30 '17 at 05:56
  • I thought about it and since this will be built into the instrument, protection is less warranted but for the external modules it will need to be added. – physiii Sep 30 '17 at 15:50

1 Answers1

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Does anyone know of a better way to accomplish this?

The signal level from a guitar can be quite low so I would be thinking of a circuit like this one (much more sensitive and can be adjusted by altering R3): -

enter image description here

Replace the microphone with the guitar and it should detect strings being strummed and rapidly charge up capacitor C2. C2 in the circuit above was intended to be low because I left the circuit as an answer to another question on activating a LED BUT, C2 can be increased to hundreds of uF to extend the delay to many seconds.

Andy aka
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  • Thank you, I updated the circuit in the original post. It does increase the number of components though. – physiii Sep 29 '17 at 21:24
  • Maybe if I add a resistor on Q3's gate it will give me better control of the delay period? – physiii Sep 29 '17 at 21:34
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    Ahh... you are modifying my circuit and using MOSFETs - that won't work properly and effectively. The whole point of my circuit is that the base-emitter of Q2 also acts like a diode (but with current gain and in a feedback path) to make what is close to a precision rectifier. So, it charges C2 quickly but discharging takes a long time. – Andy aka Sep 29 '17 at 22:50
  • Oops! I updated the schematic picture...thanks. You might be interested in the project since you seem to like that sorta stuff. I am replacing the tune/volume wiring in my epiphone les paul with a single PCB that uses a TI wireless pro audio chip. https://github.com/physiii/awesome-guitar-board – physiii Sep 30 '17 at 14:55
  • I have a couple of epiphones and don't mess with them lol. – Andy aka Sep 30 '17 at 19:13