RTD Temperature Probes Arrived

Made some progress today getting a pair of Adafruit RTD probes working with the AD7793 card today. There’s still some issues to sort out, but at least the numbers are looking more realistic. I still don’t understand the proper formula to computer the RTD resistance from the ADC value and haven’t found any clear answers in the documentation. Hope to get this sorted out soon.


Future Hardware Enhancement Discussion

The comments below were posted by Robert Adsett on the TI E2E board. With his permission I’ve posted these below to keep in mind for future hardware revisions.

Love your direction of accepting DC Power. Suspect that extending to 12-60VDC eases such DC Input

There’s a few reasons for the range I selected. Not that others couldn’t be used

  • Keeping the range above 17V or so means all the power rails can be generated with buck converters. You get +/-15V for analog easily and can even use an LDO from that to generate +/-12V. You want to use a switcher for the +/-15V because of the wide range I selected.
  • 24V is 
  • the most common industrial voltage
  • the lowest voltage node of the standard non-road EV range
  • PbS batteries argue for 1 1.5VPC to a 2.5VPC minimum range which gives an 18V lower range for the input.
  • the voltage used for large transport tractors
  • Back to CAN, DeviceNet carries 24V over their CAN cabling. Gives a ready cable standard carrying both power and data.
  • 48V is
  • the  highest voltage node of the node of the non-road EV range, at 3.5VPC this gives 60V (although you can live with 55V if you don’t have ‘hot’ batteries)
  • The DC voltage used by Telecom and data centres (also by POE). Although telecom is often -48V which might require additional thought.
  • The other common non-road EV voltage is 36V
  • 18-60V is a little over 3:1. Going over 4:1 is a bit of a step. Harder to find devices to do it and in this case you move from buck to needing buck-boost.
  • Adding a 12V node really requires dropping the voltage to 9V
  • 12V is also Automotive which brings in additional complications like load dump and drop out.

    Really it’s the industrial voltage that’s probably the most compelling, but adding telecom could be useful.

Welcome to my PMX42 computing module project!

Thanks for visiting my project page! I’ll be adding content slowly as my project develops over time. I look forward to hearing ideas from others on possible applications and uses for the PMX42. Initially I started this project with the intent of moving into some sort of niche in the industrial controls market. But, it soon became clear that the module nucleus could fit a much wider range of applications and possibilities.