John Sorensen
New Member
Here's what I want to do:
I have a reverse osmosis unit that trips on underpressure. When it trips it sounds an alarm that is at about 2-3 kHz (guessing) and plenty loud. I want to be able to detect the alarm without tampering with the circuit. So I was going to use an electret mic:
mic->amplifier->band pass filter->rectifier->low pass filter->uC.
As I've mentioned before, I'm an analog rock, and I'm stuck back on the amplifier stage. I thought I'd be doing good with an INA122 differential amp, but the DC offset is killing me. I think if I was using split supplies it would be a lot easier, but I want to use a single ended +5. I also don't want to use any exotic parts, I have a good supply of all the garden variety amps and transistors.
Anyone want to take a stab?
j.
I have a reverse osmosis unit that trips on underpressure. When it trips it sounds an alarm that is at about 2-3 kHz (guessing) and plenty loud. I want to be able to detect the alarm without tampering with the circuit. So I was going to use an electret mic:
mic->amplifier->band pass filter->rectifier->low pass filter->uC.
As I've mentioned before, I'm an analog rock, and I'm stuck back on the amplifier stage. I thought I'd be doing good with an INA122 differential amp, but the DC offset is killing me. I think if I was using split supplies it would be a lot easier, but I want to use a single ended +5. I also don't want to use any exotic parts, I have a good supply of all the garden variety amps and transistors.
Anyone want to take a stab?
j.