DIY: Digital Pyrometer Gauge

[BDCarrillo]

No calibration on mine, and a couple degrees over the 2000* span of a K thermocouple is negligible. I think onmine a few degrees is the max limit on the resolution of the analog to digital converter. The other source of error is any "cold" joint that's not of the same chromel/alum mat'l as the thermocouple. Compensators exist... LT1025As. Crappy sketch of an op-amp and compensated circuit below.

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[laserjock]

Agree, the stated precision though is +\- 1 C near room temp and 2 full scale so I'm w little wide. As long as it's a linear offset its no big deal. If it's some non-linear weirdness, it can go bad real fast over 2000 degrees. It's 5 mv per degree C so in theory the chip itself should be good to 1000c but I think it claims 750.

Anyway, just curious. I've never written code in my life so the learning curve is pretty steep but I'm starting to get there. It takes me back to grad school when I wrote my dissertation in TeX. Bonus points if you've heard of it.

 

[BDCarrillo]

Thermocouples, unlike pressure transducers, are linear... so any minor offset should be constant and a relative non-issue. Lemme rephrase my attitude towards that teensy error...5*c doesn't change how f-cked your engine is at 1400*F. Given the naturally slow response time of a thermocouple, your engine can be at a dangerous temp for several seconds before even the best gauge would show it.

With averaging it out, error induced from the ADC and voltage fluctuations should be reduced.

Now, if we were talking oil pressure then it's a different game of precision.

Codewise I have a background in VBA, which has very similar conventions to C. It's like two dialects of English. Python and Java are foreign to me and I struggle with those.

 

[laserjock]

Thermocouples, unlike pressure transducers, are linear... so any minor offset should be constant and a relative non-issue. Lemme rephrase my attitude towards that teensy error...5*c doesn't change how f-cked your engine is at 1400*F. Given the naturally slow response time of a thermocouple, your engine can be at a dangerous temp for several seconds before even the best gauge would show it.

With averaging it out, error induced from the ADC and voltage fluctuations should be reduced.

Now, if we were talking oil pressure then it's a different game of precision.

Codewise I have a background in VBA, which has very similar conventions to C. It's like two dialects of English. Python and Java are foreign to me and I struggle with those.

Agree completely with the caveaut that it is the thermocouple causing the deviation. If it is something weird with the breakout board, to me all bets are off, but I'm going to find out today.

 

[BDCarrillo]

What main board are you using, and what display?

For version 2.0 I'm looking at using a big TFT in the left side of the gauge cluster for engine temp, battery voltage, oil pressure, boost, pyro, and fuel pressure (before and after filter). I was considering tapping into the TOT sensor for tranny temp as well. Two fuel pressure sensors will let me see the pump output vs filter loss, to help figure out pump and filter health.

Using a proper TFT I can recolor the outputs (blue/green/yellow/red) for a quick visual on stats.

 

[laserjock]

Right now I'm using the Arduino Uno I've had for a year and some and haven't got to play with. I've done a good bit of work with smart relays and actually automated scientific equipment with them. I'm trying to step up my game a bit and put it to good use at home as well. The display I have is the Capacitive touch 2.8" TFT. I haven't even started messing with it other than loading a stock program and making sure it works. I think the issue will be running out of pins quickly. The touch screens are pin hogs. My plan is to put the essentials on real gauges and put all the nice to haves on a digital. There is just no place to put that many gauges in a brick nose truck and not have it turn ridiculous. I also am considering doing a board for my exhaust brake once I get it all together.

 

[mjs2011]

What main board are you using, and what display?

For version 2.0 I'm looking at using a big TFT in the left side of the gauge cluster for engine temp, battery voltage, oil pressure, boost, pyro, and fuel pressure (before and after filter). I was considering tapping into the TOT sensor for tranny temp as well. Two fuel pressure sensors will let me see the pump output vs filter loss, to help figure out pump and filter health.

Using a proper TFT I can recolor the outputs (blue/green/yellow/red) for a quick visual on stats.

What pressure senders are you using? And how affordable are they? I'd like to add one to my wvo controller and have it automatically switch back to diesel if the wvo pressure falls off, but I haven't been done any research yet on pressure senders.

Sent from my VS990 using Tapatalk

 

[BDCarrillo]

https://www.amazon.com/gp/aw/d/B00RCPDE40/ref=ox_sc_act_image_3?ie=UTF8&psc=1&smid=A1JDDORUZH3SUG

These are transducers, so it's already a 5v scaled signal, but they require 5v in. I was going to run a buck and feed the transducers and arduino board.

I haven't tested them yet... v2 with all the extras is a napkin sketch at this point.

Laserjock, you can get an ADAFruit SPI interface for capacitive touch TFTs, or their own breakout 2.8" for about 30. Hardly uses any pins.

 

[laserjock]

So this is what I bought I think.
https://www.adafruit.com/products/1947

I think I see the error of my ways now. It's not actually using all of the pins. It's a stacking problem isn't it. I knew when I bought it I thought that there would be enough pins to do stuff. I looked at it today and thought, damn... it's using all the pins.... nope.


DOH!!

 

[BDCarrillo]

So this is what I bought I think.
https://www.adafruit.com/products/1947

I think I see the error of my ways now. It's not actually using all of the pins. It's a stacking problem isn't it. I knew when I bought it I thought that there would be enough pins to do stuff. I looked at it today and thought, damn... it's using all the pins.... nope.


DOH!!

ha! I'm thinking of using the breakout screen to fit it in the gauge area a bit better, so the brain box can be up under the dash.