Hi

Im following this circuit i made on multisim it basically turns on if the temperature is to low or to high. the problem im having is that when i make it on breadboard both leds are on, Im using an LM35 temperature sensor and LM741 as my comparator.

im getting all my calculated values on the inverting and non inverting pins.

any help

 

Hi

Im following this circuit i made on multisim it basically turns on if the temperature is to low or to high. the problem im having is that when i make it on breadboard both leds are on, Im using an LM35 temperature sensor and LM741 as my comparator.

im getting all my calculated values on the inverting and non inverting pins.

any help

Your circuit doesn't work because you are attempting to operate the LM741 with its inputs outside their common-mode input voltage range, and you are attempting to operate it at a lower supply voltage than it's capable of working at. The 741 isn't suited for 5V single-supply operation.

Read the data sheet: http://www.ti.com/lit/ds/snosc25c/snosc25c.pdf

You would be better off using an opamp capable of low-voltage, single-supply operation, like the LM358 (dual) or LM324 (quad). Even better would be a proper comparator IC such as the LM339 (datasheet at http://www.ti.com/lit/ds/symlink/lm339-n.pdf).

 

All of which says that the Multisim '741 model isn't worth a crap!

 

i replaced the IC and it works well with LM324 thank you!

 

i replaced the IC and it works well with LM324 thank you!

Excellent!