Are the two grounds electrically the same?
No, different GND pins.
Not sure about the two power buses, are they from a different source?
No, same source. What I mean by power bus is that I've got a breadboard with two buses going down each side. I'm connecting the LEDs to one and the sensor to the other. Each connected to a separate ground pin.
Either way, as I said, that simply can't happen if it is wired as described. Think about it, all that you are doing is adding a capacitor across the supply, this can't affect the signal. What were you seeing that made you think there was a delay.
Ok, here's my data. Numbers on right of graph are values I've received from ADC, the graph is a representation of those numbers. ON represents when the LEDs are switched on, OFF when they are off:
With no caps:
With 235uF on LED circuit:
With cap on sensor circuit:
It sure does look like the signal is being delayed. That or its being inverted. Oh, BTW, the values were taken when the sensor was partially blocked from the IR LEDs.
Thanks for this. I'll have to read it later.