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<SOLVED> Using Arduino to sense temp (automotive)

Posted: Sat Oct 19, 2013 3:05 am
by DaveJ
Hi All,
I want to be able to sense temperature of an engine using a standard 40 - 120 degree VDO sender unit. I want to use ATTiny85 with AnalogInput(). The docs use a pot with one end connected to +5v, the other connected to GND and the wiper connected to an analogue pin.
Could I do it like the attachment so I can connect it to a single pin VDO temp sender unit?
Thanks for your help :)
Alternate analogue input.png
The 10k pot is the VDO temp sender unit

<SOLVED> Using Arduino to sense temp (automotive)

Posted: Sat Oct 19, 2013 8:39 am
by DaveJ
I have since researched and found that this is the correct way of interfacing with a thermistor such as a coolant temperature sensor for an automotive application.
To get a readout temp you would need to use the Steinhart-Hart equation and find the values for A,B and C
See here --> Steinhart-Hart equation on Wikipedia
To get these values you can use an online calculator for NTC thermistors
And the resistance / temp scale for the VDO sensor (if you are using it) PDF format
I used this tutorial (PDF format) to work out what the heck I was trying to achieve. :)
I hope this will help someone else one day,
Regards,
Dave...

Re: <SOLVED> Using Arduino to sense temp (automotive)

Posted: Fri Sep 26, 2014 10:50 am
by MikeLikes
Hi Dave,
I would like to read some analog sensors / senders on an old car (pre obd). I am trying to find the tutorial that you used for reading the VDO sensor. Are you able to tell me where I might be able to find it.

Regards,
Michael

Re: <SOLVED> Using Arduino to sense temp (automotive)

Posted: Sun Oct 05, 2014 10:56 am
by DaveJ
Hi Mike,
For memory all I did in the end was to get hold of the datasheet from here --> http://www.bosch-motorsport.de/media/ca ... 739pdf.pdf
Then worked out the voltage divider needed to get a reasonable voltage at the arduino for the temperature ranges needed. The formula is here --> http://www.electronics-tutorials.ws/resistor/res_3.html scroll down until you see about the voltage divider :)
I hope this helps :)