Corvair Forum

67monza wrote: ↑Fri Apr 04, 2025 9:38 am

66vairguy wrote: ↑Fri Apr 04, 2025 8:32 am characterizing the curve ... thermistor conducts amperage it "SELF HEATS"

Indeed, it's a nightmare. My middle indication is good, but the rest is a mess. I just ordered some arduino nano boards. Long overdue to start playing with those.

Buy a good Arduino book, or books. There are thermalcouple to Arduino chips with cold junction compensation (must use this type), but most are NOT ground isolated. You must use a thermalcouple that is NOT grounded to the shield cover. That gets tricky as many are lower temperature (insulation). I did look at using a floating ground interface, but it just adds more complexity (and signal noise) so I went with a non-grounded thermalcouple. The Arduino doesn't like "car" power (11.5 ro 15VDC) although it will work, but the onboard volatage regulator can run HOT above about 10 VDC (not good for the board). I use a DC to DC micro power supply to convert to 7VDC to the Arduino power input. That eliminates any "electrical" noise glitches. DC to DC units don't generate much heat, unlike the old analog regulators.

KEEP IN MIND MOST OF THESE CHIPS and BOARDS ARE MADE OUTSIDE THE U.S.A. so the prices WILL be going UP!!!!! While there is very little "labor" involved in making chips and boards, companies in the U.S.A. have never been interested low volume manufacturing. Fortunately companies in other countries are.

The high volume advanced chip manufacturing goes off shore since Taiwan can make high quality advanced chips for less than ANYBODY. Just amazing. That said with China threatening to take over Taiwan that may all change. Yes the Binden folks got Taiwan chip companies to build plants in the U.S.A, BUT according to the business news it is NOT going well. The level of engineering and build quality by U.S.A. contractors is inferior and has set the plant building back by YEARS with build budgets going over estimates and no doubt what will be produced WILL cost more!!!

66vairguy wrote: ↑Fri Apr 04, 2025 10:16 am Arduino book

I'm getting into this now. Curious, did you essentially do analogRead lookup table analogWrite? If you happen to want to share any code, please do. My C is rusty.

67monza wrote: ↑Sun Apr 20, 2025 9:06 pm

66vairguy wrote: ↑Fri Apr 04, 2025 10:16 am Arduino book

I'm getting into this now. Curious, did you essentially do analogRead lookup table analogWrite? If you happen to want to share any code, please do. My C is rusty.

You can do that, but you have to be a very sharp coder (I am not) and deal with a NOISY electrical environment of a car and thermal couple variations, not to mention building a cold junction compensation circuit!!!!! No need as there are some good thermal couple read micro boards with their own code for little $$$. Check out Adafruit MAX31855 and they have a library of code you just plug-in to talk to the Arduino board (although I had to revise their code and that takes some skill to modify an existing library code, but doable if you like to read a lot

NOTE: Most thermocouple boards DO NOT HAVE ground isolation so you MUST use a thermocouple that is insulated from the shield jacket (grounded) and they have a limited thermal range (insulation melts if it gets too hot). This was a issue for me and I ended up building my own!!!! Yeah it get complicated. You can use a grounded thermocouple made for high temperature use, but then you need to install an opto-isolated bi-directional data board between the thermal couple board the the Arduino board. I just did not want to deal with the extra parts (more parts, higher failure rate, bigger package).

Remember the temp gauge is NOT powered by the driver - the thermistor sinks amperage (via changing resistance to temperature) to make the gauge work. You could use a analog driver circuit, but you have to be a really good analog designer and there is usually an issue with heat. I chose to drive the magnetic gauge like a motor using Pulse Width Modulation (PWM) that most Arduino boards have to drive LEDs' (that is why on cars you video the LEDS blink because the video frame rate is out of sync with the LED blink rate (too fast for human eye to see - just appears dimmer). When driving motor you will need a FAST power switching transistor and resistive load --- creates less heat!!

If nothing else you will have fun (and frustration) learning something new.