On the synth, a lever controls the volume with a hall effect sensor. The sensor's output is processed with the Arduino, which I can convert to a PWM output.
Using a digital potentiometer will not work, since I need the signal's voltage to drop to zero.
I also tried controlling the voltage into the signal generator chip's VCC pin, but bizarrely I discovered that whatever is input into the chip makes no difference on the signal, even if there is no voltage going in at all. I don't know why this happens.
It doesn't matter if the VCC pin is connected to 5v or nothing at all, there seems to be no change. It must be getting power from one of the data pins instead.
Are you talking about the output of the AD9833 chip not changing when its Vcc is disconnected or the output of the preamp when its Vcc is disconnected?
When you talk about changing the output level with PWM are you talking about the PWM output from the Arduino that is controlled with the Hall devices? Also, to be clear, this output level you are talking about, is it the output level of the preamp?
The output of the AD9833 chip does not change when its Vcc pin is disconnected.
The PWM output level is controlled by the hall effect sensor.
I would be fine with either the output of the preamp or the output of the signal generator is changed, as long as the final output (of the preamp) can be lowered to 0.
It's still producing the same output without its Vcc input, so it must be getting powered by one of the data pins attached to the digital outputs of the Arduino.
Vcc is the frontmost pin with the square pad. Since it's a breakout board it's probably just wired differently. I'm getting the expected output voltage, so it's not a broken board.
Stop powering the Vcc pin? I won't, anymore, but when I was powering it everything seemed to be functioning normally, with nothing heating up. Surely connecting the pin as intended wouldn't damage the board?
Personally, I would try doing it with a digital pot first but it's possible that there could be some coupling of the unattenuated signal to the output through capacitance. Probably less likely if you attenuate the 600 mV input to the preamp as opposed to the preamp output.
It's not intended to be powered through the Arduino interface is what I'm getting at. It should have its Vcc/Gnd powered whenever there are other voltages on its inputs/outputs.
