I am new to Arduino and the choices are bewildering. I'd appreciate guidance in selecting the best hardware solution for my project. My project is to create a fuel totalizer for an amateur-built one-man helicopter. I want to input 0-5 volt values from two capacitance fuel probes that are measuring fuel levels in two irregularly shaped tanks, then using look-up tables to account for the irregular shape of the tanks, convert the raw values to fuel quantity in each tank, combine the two, convert back to 0-5 VDC and drive an analog fuel quantity indicator. The indicator has a 270-degree sweep, so to make it read smoothly I would like at least 9 digits of precision, although 8 might work. Speed is not an issue so I could multiplex the two inputs to a single ADC. To avoid EMI problems differential inputs would be necessary. All help would be much appreciated!
juan@helicycles.org
The ATMega chips the classic Arduinos are based on all have an ADC with 10 bits resolution and a reasonable degree of precision and accuracy. They also have a built-in 4 (or more) channel analogue switch, so you can easily handle tasks requiring 2 or more channels and sampling rates up to a few KHz. The ADC and analogue comparator can be referenced up to the value of Vcc (usually 5V) with no trouble.
Inputs are single-ended though. You'd have to make up your own differential front-end.
The ATMega doesn't have a DAC, but it does have good support for pulse-width modulated digital outputs. These can but run through a low-pass filter with a cutoff of 0.5 Hz or thereabouts and could go into a moving coil meter just fine.
Would it be possible to add something like the MCP4725 12-bit DAC and the ADS1115 ADC from Adafruit using a daughter board? That looks like it might give me the differential I/O I'm looking for.
Do you mean this --> Overview | MCP4725 12-Bit DAC Tutorial | Adafruit Learning System
Yes. That looked like an inexpensive way to get me the 0-5 volt output I need with enough resolution to satisfy my needs. But how do you interface to the processor without using a proto-board and jumpers? I want to make a circuit that I can actually use in my helicopter and not just play with on the bench.