ATMEGA328P Internal Temperature Sensor Bias

While testing on it’s own, without any peripherals, the ATmega328P does a  good job in temperature measurements.  The question that comes to mind is, “What happens when this chip starts to source current?”.


For my little project, I am looking at 15mA pulse for the radio Tx and an occasional Tx LED blink of 13.6mA.

Since there are three LEDs on the board already, 40mA should be enough to test with.

Using the same sketch as the Hidden Response Accuracy in the ATMEGA328P, I commented out the LM35 measurements and added a Blink without Delay for the (3) LEDs.  

Tests included were:

  • Measure every second and toggle the LEDs every 10 seconds
  • Measure every second and toggle the LEDs every 2 minutes
  • Measure every second with the LEDs always ON


Atmega Temp Toggle


While there is an obvious bias with the “Always On” chip heating, the reduced duty cycles can help dissipate some of the heat generated internally.  I would imagine 100mA total sourced current will make this a problem for a project requiring <3°C accuracy.


Posted on January 25, 2014, in ATmega328. Bookmark the permalink. Leave a comment.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: