Multisim and Ultiboard

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LED does not work



I am trying to test a circuit using multisim, and simulating it.   The LED3 does not flash like the lamp which is in the same circuit ! .  Also, at times, It gives convergence error.


Please someone help.  I have spent hours .  


Thank you.

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Message 1 of 5

Hi there,


In your circuit, the on current for LED3 is 5mA, the resistor you choose is 2.2k which is a little bit bigger that LED3 cannot turn on. Try to change it to 1K and then you will see it's flashing now.






National Instruments
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Message 2 of 5

So I have a similar issue in my circuit design and I cannot figure this out.

-using 2 input and operation

-both connections are closed

-5v dc power

-1k resister

-led does not light up?

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Message 3 of 5



Your LED is inverted. Reverse the connection of anode and cathode. You might also want to increase the brightness of the LED. This can be done by lowering the series resistance. The appropriate value depends on actual application. For your experiment try between 200 and 300 Ohms.


Best regards,

G. Goodwin

Message 4 of 5

Ah, Thank you so much!

Message 5 of 5