I’m currently doing a small project. I’m trying to make my first pcb.

That’s for a light I made.

But the LM35DZ outputs a wrong voltage.

My LM35 puts out 4.6V instead of 380mV.

With a 12V - 2A power supply.

With the datasheet I can’t find the maximum input current.

Do you have an idea?

This is my circuit:

enter image description here

Datasheet : https://www.mouser.fr/ProductDetail/Texas-Instruments/LM35DZ-NOPB?qs=QbsRYf82W3F5RpWTxhXHxA%3D%3D

The component is wired to the CN1 jst

R6 : 47 ohm R5 : 330 ohm

With a 3,3V linear regulator.


closed as unclear what you're asking by Elliot Alderson, Dave Tweed Apr 26 at 23:53

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    \$\begingroup\$ Please add a link to the datasheet into your question using the edit link below the question. Note that you can make your schematic much more easy to read by using GND symbols close to each component attached to ground instead of wiring. Also note that there is no LM35 in your schematic. Welcome to EE.SE. \$\endgroup\$ – Transistor Apr 18 at 18:58
  • \$\begingroup\$ The LM35 is probably intended to be connected to CN1. \$\endgroup\$ – JRE Apr 18 at 19:52
  • \$\begingroup\$ Are you sure about the values for the voltage divider R5 and R6? That's probably not the cause of the problem with the LM35, but certainly looks odd. \$\endgroup\$ – JRE Apr 18 at 20:07
  • \$\begingroup\$ There is the datasheet for th lm35DZ/nopb :mouser.fr/ProductDetail/Texas-Instruments/… \$\endgroup\$ – CharlieWhite Apr 18 at 20:08

The LM35 was damaged. miss wiring. Because of that the LM35 ouput a wrong voltage when it was correctly wired. Thank you for yours helps.


The Mouser link clearly indicates

Output Current: 10 mA max

However, it will not pull down negative bias current since the sensor uses an NPN emitter follower output inside a feedback loop with low quiescent current.

Therefore put a resistor on the signal input of the floating LM324 (PNP inputs) to ground e.g. 1k to 10k.


I don't see anything wrong with your circuit up to the LM324 input. Check that the LM324 GND pin is actually connected to ground, and check the wiring to the LM35. Check it with a meter.

If the LM324 GND is open, the several mA current will exceed the ~1uA sink capability of the LM35.

Failing that, perhaps you have a mis-wired or damaged LM35, but you have not provided a schematic for that part of the circuit.


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