The DC output of the opamp has a max output of 1.2V to 7.8V when its supply is 9.0V. The output DC voltage is 4.5V without a signal.
If the opamp's output is capacitor coupled to an ordinary diode that feeds a filter capacitor and a load resistor to ground then the max output to the encoder is only +2.65V.
But since the encoder needs an input of 5V then a DC amplifier must be used. A TL072 dual opamp can be used and its second opamp can be a DC amplifier. Its input must not be less than about +3V so level shifting must be used.
sooo, its built finally and ive just tryed to test it. ive got 9v on the board, and I put the scope on 500mv and can see some movement in the signal from the mic on pin 3 of the TL071
I appear to be getting 0v out of the opamp on pin 6 even when blowing into the mic.
any ideas what the problem could be or what to look at next?
sooo, its built finally and ive just tryed to test it. ive got 9v on the board, and I put the scope on 500mv and can see some movement in the signal from the mic on pin 3 of the TL071
I appear to be getting 0v out of the opamp on pin 6 even when blowing into the mic.
any ideas what the problem could be or what to look at next?
Maybe you connected the electret mic backwards. The ground pin also connects to its metal case.
Maybe the load at the output is less than about 2000 ohms.
I've learnt more from being helped on here than I have in donkeys years of messing around on my own.
Heres a link to a little vid of the op amp (you probably wont apprieciate the music lol) in action with the mic next to the speaker **broken link removed**
now on with the next challenge of tripping my encoder
The output of the opamp is a positive DC voltage that is modulated more positive and less positive by the signal.
The capacitor charges to the DC voltage so the average output voltage from the capacitor is 0V which is modulated up (positive) and down (negative).