Making a high resolution ADC from an Arduino Mini Pro
I want to make a high voltage Geiger/ Photo Multiplier Tube (PMT) supply that is regulated by an Arduino UNO or Mini Pro. The Arduino would need to control the voltage by reading if it is above or below target then adjusting the voltage as necessary, as a side job it will set the user programmed voltage and also display the target output voltage to an LCD display. Since the high voltage supply may go to over 1.5KV and I want very fine resolution control of less than 250mV, this means as a minimum I will need to be able to read back at least 6000 discrete steps. Is it possible? Yes I do think it should be possible, the atmega328 is quite a capable little micro-controller and with just a handful of low cost external components (some resistors, capacitors, and a comparator) it should source a high resolution voltage as well as measure one. Lets find out at the Mad Scientist Hut.
I will do this in several steps over many days or weeks, here is my plan of attack:
1) Create a high resolution Digital to Analog Converter (DAC) source.
a) We need a 16 bit PWM output from the Arduino. (Completed 4/4/15 ) Click here: Link to this article
b) We need to filter the PWM signal down to a usable stable DC value. (Completed 4/5/15 )Click here: Link to this article
c) Lets verify the Integrated Non Linearity (INL) , Differential Non Linearity (DNL), Gain and offset of the DAC source just to see how good it actually is. (In progress 4/11/15 )Click here: Link to this article
2) Create a high resolution Analog to Digital Converter (ADC) measure system.
a) The compare circuit.
c) Lets verify the INL, DNL, Gain and offset of the ADC just to see how good it actually is.
3) Finally the High Voltage supply.
a) The HV generation.
b) Control and measurement.
c) How well does it work?