Simple Vco Circuit. You may have noticed that the circuit has both a positive and a negative supply voltage. Luckily for us this circuit works very well using the negative voltage generator project so make sure to build that first.
1 the circuit 2 calibration and first tests a. Using a 1 v input the oscillator s output frequency is around 1500 hz. This circuit is also present in the vco section of the dm77 drum module.
All s left is decoding by measuring the frequency of these new ac voltages on your phone.
1 the circuit 2 calibration and first tests a. Super cheap and easy. Congratulations you can now send information to your phone over an audio jack. Now we will build a voltage controlled oscillator with a 555 timer chip.
