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Help please, will this circuit work.

pembp

New Member
Can anybody advise me if the circuit attached will function as required.
The external timer supplies a 6 volt signal to the relay coil for between 3 & 9 seconds, this in turn drives the 12 volt motor for the 3 to 9 seconds & it also charges the 220uf capacitor.
At the end of the 3 to 9 seconds, the Piezo buzzer should continue to sound for a further approximate 80 seconds via the N channel MOSFET.
Any help appreciated.

F+Buzz.pngF+Buzz.png
 

alec_t

Well-Known Member
Most Helpful Member
Welcome to ETO!
1) The diode is the wrong way round.
2) The FET 'on' time will depend a lot on the Vgs threshold. Simulation shows that to get 80 sec you'd need a FET with a threshold ~1V. One with a 4.7V threshold would give only ~30 sec.
 

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