What sits between Automation Hat analog inputs and the ADS1015?


#1

I ported some ADS1015-specific C code to the Raspberry Pi so I could use it on a project I’m working on. I went several days scratching my head - the readings just didn’t make any sense. Then a careful reading of the Python library revealed that the output is scaled by 25.85V!!

I can’t seem to find any schematics for the Automation Hat nor is there any mention of what kind of scaling was implemented. Can someone let me know what that might be? And more importantly, is there any way to defeat or bypass this scaling? Maybe I can do a little rework to the board – remove a component and replace it with a wire, perhaps?

This is important because the signal I am reading will roughly be in the 0 to 1V range. I’m afraid this voltage scaling will destroy most of the devices resolution.

Thanks in advance!


#2

For the 25v tolerant inputs the voltage is divided by a basic resistor divider which scales 25.85V down to 3.3v.

I go into a little more detail about what this means for sensors with a low-voltage output here: Automation phat compatible sensors

On Automation HATs 3v3 header there is a 4th, unscaled, 0-3.3v ADC input which you could use.