Temperature sensor

Hi

I followed this guide to interface with a LM35 temperature sensor:

http://www.danielandrade.net/2008/07/05/temperature-sensor-arduino/

The reading appeared very accurate over USB, but when I hooked it up to a mains power supply it suddenly began to vary wildly (sometimes as much as +-10 degrees.

(http://tweetphoto.com/8634960)

This makes it pretty useless to me. Has anyone else experienced this before?

Thanks

Ross

It looks like your power supply is noisy and you could do with more decoupling. http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Yup, looks like that might do the trick. I'll give it a try.

Ta

Ross

Uncanny! I was going to post on here tonight about this very same problem.

Just read the link about de-coupling. One quick question if I may....

I've got my ATMEGA168 sat in a socket soldered up on veroboard. The 5V supply comes from a 7805 voltage regulator which has a 10uF electrolytic capacitor across the output terminals.

Should I be looking to replace that capacitor (as a starting point) with a 47uF electrolytic capacitor and also use a 0.1uF across the ATMEGA's VCC and Supply pins?

Sorry for hijacking the thread.

Should I be looking to replace that capacitor

No don’t replace, add to the capacitors a 0.1uF for the HF noise.