I don't want it to hold the value at all. This is for a midi drum pad, so I need a circuit that will detect the peaks very quickly.You need a bleed resistor across the capacitor, otherwise the output will stay indefinitely at the peak voltage or drift to one of the rails.
How long do you want the circuit to hold the peak value?
can you tell me what I'm doing wrong? I have 5 volts connected to the vcc terminals and the piezo connected to v in and gnd. but I get nothing when I hit the piezoThat's the classical circuit. Just make sure C is low leakage and temperature stable.
If you don't want to hold the peaks then you don't want a peak detector, since that's what they do.don't want it to hold the value at all. This is for a midi drum pad, so I need a circuit that will detect the peaks very quickly.
I suspect a problem with the common-mode input voltage range.can you tell me what I'm doing wrong? I have 5 volts connected to the vcc terminals and the piezo connected to v in and gnd. but I get nothing when I hit the piezo
And only with a DC path to ground for the hold capacitor, as I previously noted.The circuit you're using is only good for holding the peak voltage.
http://drummaster.digitalcave.ca/drummaster/design.jspIf you don't want to hold the peaks then you don't want a peak detector, since that's what they do.
So what do you want the circuit to do with the peaks once it "detects" them?
And only with a DC path to ground for the hold capacitor, as I previously noted.[/QUOTEl]
http://drummaster.digitalcave.ca/drummaster/design.jsp
When I add a diode or a cap to the piezo the signal becomes too week so that's why I tried the op amp.
Thanks, but could you draw the circuit? I'm not experienced with thisThere is no DC bias path at the opamp input either.
A piezo looks like a capacitor, you need at least a high value resistor from input to ground to bias the input stage.
That peak hold circuit has a reset switch for the capacitor, which is necessary if you don't have a resistor, and which you don't have in your circuit.
I would be happy to, but you have not defined exactly what the circuit function is.Thanks, but could you draw the circuit? I'm not experienced with this
Can I use the ne5532 op amp instead of the lm324? I don't completely understand how this works, I never used op amps before. I thought I could use this simple circuit but it made the piezo signal to weak so I was trying amplify the signal with an op amp. The drum pads are velocity sensitive so the AD converter has to have a definite peak. I wanted to keep it as simple as possible because I have 24 pads and need to build a circuit for each pad.Something like this?
You can change the value of R3 to get the filter decay time you want.
View attachment 155956
Yes, but as I noted, that will require a dual supply, whereas the LM324 is designed for single supply operation so only needs one supply.Can I use the ne5532 op amp instead of the lm324?
I have either 5 or 3.3v, I don't know how to measure the impedance, all I have is a multi meter. I would like to use just one of the ne5532s op amps per channel since I already have them. I have enough to use 2 if needed. if you could put a schematic of the circuit up with any known values I'd really appreciate it.Yes, but as I noted, that will require a dual supply, whereas the LM324 is designed for single supply operation so only needs one supply.
What supply voltage(s) do you have?
What is the impedance of the circuit that this signal feeds into?
If it's high enough you may be able to get by with just one op amp per channel instead of two.
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