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[SOLVED] 74HC08N doesn't latch ?

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Kandy Boy

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Hello , I need some help pls, I am using the SN74HC08N chip. Why doesn't the first AND gate latch itself ?

I have connected the output of the first AND gate to its own input.

After I release the button , the diode should take care by feeding the current from the output back into the input , why this doesn't happen , the LED is not always turned on after I press the button once.

I really need advice on how to latch it

Thanks you all !
 

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Solution
The output of the 74HC08 will be prevented from going to a high enough voltage because the LED will peg it at about 1.6V.
Try adding a 1K resistor in series with the LED.

Brian.

betwixt

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The output of the 74HC08 will be prevented from going to a high enough voltage because the LED will peg it at about 1.6V.
Try adding a 1K resistor in series with the LED.

Brian.
 

    Kandy Boy

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Solution

KlausST

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Hi,



some general rules:
* use a fast ceramics capacitor with very short connection to every VCC and GND of every IC.
* don´t leave any (unused) input floating. It may cause various problems.

Klaus
 

    Kandy Boy

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Kandy Boy

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The output of the 74HC08 will be prevented from going to a high enough voltage because the LED will peg it at about 1.6V.
Try adding a 1K resistor in series with the LED.

Brian.
Thank you very much , your solution worked out!
 

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