Hi all,
I have a project that I've been working on for fun, but still can't seem to get it to work the way I want it to. What I want to make is a circuit that will allow me to close a circuit when a certain frequency is detected. Amplitude is not important for the applications I want to use it in, only the sound frequency.
In addition, I would like to be able to set a delay for the signal so that it would have to be present for a certain amount of time before activating the switch.
My original plan was this: Electret mic->Gain Amp-> Active High Pass Filter-> 555 Time Delay Circuit -> MOSFET switch.
The idea was that I could amplify the signal off of the mic, filter out lower frequencies, then have a 555 circuit set for a delay. The output of the 555 would be used to trigger the MOSFET and close the circuit.
Where I'm having trouble is the signal is not being filtered well enough, and I think this might be because it's a first order filter. I can maybe just fix this later. I think I'm also running into problems with the 555 as my delay since the input is more or less a sine wave- can 555's work this way?
Thanks in advance for any help, I'm not well versed in building circuits like this. Also I'm only looking for ideas on how this could be made better, not specific values for components.
I have a project that I've been working on for fun, but still can't seem to get it to work the way I want it to. What I want to make is a circuit that will allow me to close a circuit when a certain frequency is detected. Amplitude is not important for the applications I want to use it in, only the sound frequency.
In addition, I would like to be able to set a delay for the signal so that it would have to be present for a certain amount of time before activating the switch.
My original plan was this: Electret mic->Gain Amp-> Active High Pass Filter-> 555 Time Delay Circuit -> MOSFET switch.
The idea was that I could amplify the signal off of the mic, filter out lower frequencies, then have a 555 circuit set for a delay. The output of the 555 would be used to trigger the MOSFET and close the circuit.
Where I'm having trouble is the signal is not being filtered well enough, and I think this might be because it's a first order filter. I can maybe just fix this later. I think I'm also running into problems with the 555 as my delay since the input is more or less a sine wave- can 555's work this way?
Thanks in advance for any help, I'm not well versed in building circuits like this. Also I'm only looking for ideas on how this could be made better, not specific values for components.
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