Hello,
I am trying to build this circuit, coming from an article about gesture controllers for music (http://cnmat.berkeley.edu/system/files/attachments/currentmodefinal3.pdf)
This circuit is supposed to allow one to get simultaneously x, y and z values for a 4-wire resistive touch-screen (actually the author uses a trackpad but it functions with the same resistive principle).
Here's the description of the circuit: "The solution developed by the author is to provide a small constant current through the touch pad array inverting op-amplifier shown in Figure 8. This is similar to the approach Moog employed on his 926 duo keyboard. The inverting input is a virtual ground at the same potential as the non-inverting input. The current through the pad resistors is established by two constants in the circuit, the summing node input resistor R and the source voltage reference applied to one leg of this resistor. The three measurands (XYZ) are computed by subtraction of the three op-amp outputs. The op-amps should be selected to have low input offset voltage. External noise sources are controlled by limiting the op-amp bandwidth with a low value capacitor from its output to the summing node (C)."
There is a raw schematics in the article, duplicated here in the first picture.
I have good op-amps at hand (AD620) but they need dual power supply while those shown in the schematics use a single supply. I have adapted the schematics to those op-amps with the addition of a special IC providing dual supply from a single one I do also have at hand (Maxim 680), which should allow me to connect the circuit to an Arduino.
However I am not sure my adaptation is correct. Can someone give an opinion about it (please see second picture) ?
Thank you in advance.