Temperature Controlled LEDs using LM35

Justin Jones's picture

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Joined: Oct 23, 2018

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Temperature Controlled LEDs using LM35
November 13, 2018 - 8:32am

I'm working on the temperature controlled LED project from the site

 

https://circuitdigest.com/electronic-circuits/temperature-controlled-led...

 

and I am running into the problem of only the RED LED glowing and not the YELLOW when the case should be the YELLOW LED is glowing and the red when heated. I have the circuit hooked up as it is described in the instructions.

Aswinth Raj's picture

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Check if yellow LED is in working condition
November 13, 2018 - 11:45am

Use a multimeter to check if the yellow LED is in working condition. 

Also what do you mean by this line?

when the case should be the YELLOW LED is glowing and the red when heated.

Justin Jones's picture

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I mean that the red is
November 13, 2018 - 11:50pm

I mean that the red is glowing as soon as I hook up the power supply the red is heated. Instead of red the yellow should be.

Abhishek's picture

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Most probably the issue is
November 13, 2018 - 12:08pm

Most probably the issue is with the reference voltage of LM358, try adjusting the reference voltage by rotating the potentiometer till the point where yellow LED starts glowing.

Also check the connections again, specifically with LM358.

Justin Jones's picture

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I've checked both of those. I
November 13, 2018 - 11:50pm

I've checked both of those. I will try to rebuild the circuit and see if anything changes.