K8055: Strange behaviour of ADC

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1

Hi,

I read temperature from a LM35 via ADC input.

when I read the ADC and the notebook works with battery w/o power supply, it works perfectly. :smiley:

But when I connect the power supply of the notebook, the ADC becomes crazy. :?

When I disconnect the power supply it is ok again. Unfortunately, I need to work with the power supply. :cry:

Do you know, what’s happening here?

Thanks a lot!

2

You have a “GROUND” problem, Check the ground of the power supply for the LM35 (try another).
Try to take just 5V from the PCB because the consumption of the LM35 is verry low, so it’s no problem.

3

Hi VEL Support,

thank you very much for the tipp.

I took the 5V from the K8055. It works better, but unfortunately still not better enough…

With the notebook w/o power supply -> ADC Value = 46

With the notebook w/ power supply -> ADC Value = oscillate between 30 and 60.

I think that you are right… it seems to be a GROUND problem.

Do you have maybe another tipp to correct it?

Thanks a lot!