Active voltage divider?

[oddson]

I'd like to make an expression pedal with a hall-effect sensor that can mimic a voltage divider where the voltage to be divided is not necessarily the same as Teensy's signal voltage.

The two methods that occur to me are:


1) a digital potentiometer controlled directly by the Teensy as an actual voltage divider

2) some sort of control circuit that applies a fixed gain to a filtered PWM output signal from the Teensy -- where the gain is the ratio of the external rail voltage and Teensy's operating voltage



I just can't figure how to set the gain to the ratio of the two reference voltages.


Any comments on how to realize the second approach (or anything better)?

 

[oddson]

Some observations since posting:

Digital potentiometer originally seemed like overkill but they are cheap at a resolution that can match the effective resolution of the sensor (especially as most of the time they'll get turned into 7-bit midi anyway) ...this is now my fallback

There are analog multiplier/divider chips that implement a generalized transfer function that can output y=xv/u -- but they are NOT cheap (which is weird as they're fairly modest circuits).

I could probably figure out the originally sought after control circuit from op-amps and discreet components but it occurs to me it might better to convert the signal voltage while its still digital and then low-pass the output to a smooth control voltage.


This is easy enough if I could assume the voltage to divide would be <=5 volts but I think it might be beneficial to support at least to 10 volt and maybe 12 volt.

Still open to suggestions.