029q fan on/off temps

Natedogg · Post by **Natedogg** » Sat Apr 29, 2006 1:08 pm

I got the fan control/LED18 working today in 029q. It works great, but the temps are off. I want it on at 205 and off at 197. It comes on at 203 and doesn't shut off becuase the temps won't drop below the thermostat temp (195).

I had to set it to 209 on and 203 off to get it to come on at 207 and off at 197.

Anyone else noticed this?

Nate

davezed · Post by **davezed** » Sat Apr 29, 2006 6:54 pm

Nate
Might be wrong but I think you will find this sort of thing with all HC908 based MS. It's because of the resolution of the 8 bit AtoD convertors reading the sensor. The HC12 based processors have 10bit AtoD's therefore have improved accuracy.
If you look at MT reported temps on the simulator you will find temp rises as follows: 194, 197, 200, 203, 207 210 etc. This would mean you probably would have to set 202 to have it come on by 203 and 200 to turn it off by 197. This is what I have found but I guess others may think different??

Cheers
DaveZZ

Post by **jsmcortina** » Sun Apr 30, 2006 3:18 am

Good response. Depending on the temp sensor and bias resistors used the temps are indeed quantized so will step up like that. Stim testing is the best way to see what will happen.

Jame

KariM · Post by **KariM** » Tue May 16, 2006 6:50 am

Edited: The message I replied seems to have disappeared, so the reply was pointless on its own.