Temp sensors erratic with 9 volt power

I am using a Boarduino board connected to 2 lm335 temp sensors. Project works fine when powered by usb power, but sensors read erratic when powered by wall wart or 9 volt battery power.

I am using a Boarduino board connected to 2 lm335 temp sensors. Project works fine when powered by usb power, but sensors read erratic when powered by wall wart or 9 volt battery power.

There are two versions... One with a linear regulator and one without... V1 & V2.

If you are using V1, you should be OK. If you were using V2, you need external voltage regulation for a wall wart or 9V.

Inexpensive wallwarts are notorious as being cheap power sources for Arduino.
9V batteries often cannot supply a stable current as they age.

Ray

I am using v 1.0. I have built the the exact same circuit and have the same results on a arduino Uno. The readings jump by sometimes 10degrees fahrenheit on the wall wart and 9 volt battery. With the usb plugged in varies only by 2.
P.S. I am not using the adjust pin. I have checked voltage and amp(1.12ma) readings and they seem ok.

I have built the the exact same circuit and have the same results on a arduino Uno.

New information!

The only thing common is the wall wart.

Patient says, "Doctor, it hurts when I do this..."
Doctor says, "Don't do that!"

Build or invest in a suitable AC power supply. You may also be having stray AC induced currents in the resistor-thermistor junction, it is OK to decouple it for RF to Gnd with a 100nF.

Ray

Problem solved. I hooked up an oscilloscope and found no noise on the 5v or 9v rails or the analog output of the temp sensor. I noticed when scope was disconnected it gave erratic readings of temp sensors. When scope connected normal readings. I have since grounded the ground rail to a 120v ground and everything fine. Is this acceptable to have it grounded in this way? Thanks for your help sometimes its the simple things that
make it difficult.

Ray, did you post in the wrong thread by accident?

...R

I know in the U.S. that the 120 VAC should have a solid copper wire back to the fuse/beaker box and the grounds there are referenced to the power company ground and one or more ground rods at the customer home. This is used by GFI as a reference for safety purposes. My bench antistatic mat came with a plastic adapter plug where the mat is connected to the ground prong. The metal outlet boxes should have a ground screw so that the box and screw holding the coverplate is at ground.

I think if your arrangement works for you, you should be fine. Just remember, it is a small lightning rod, so static discharges from shuffling may create enough EMP to reset the Arduino if not in a metal project box.

Ray