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how to interface a digital IC with an LED

Hello, I would like to hook up LEDs to a decoder and was wondering how to do this.. I basically want to use a counter wired to the decoder and have an LED associated with each output of the decoder and have them flash on consecutively one after another...

I've been looking at some HC and HCT family decoders, but they drive around 20mA and output a low of 0 volts and high of 5V.... I'm not sure what's at the outputs but would I need a pull up resistor in line with an LED to get this to work?

I would also like the outputs of my decoder to also go to a logic gate like a nand or or gate... I'm not sure if that's important with regards to the making the LEDs blink at this point...

much thanks

Reply to
panfilero
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For $6 this might work for you.

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You will find many do it yourself products at this website.

Kind of makes me miss good old Heathkit!!!

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Christopher

Temecula CA.USA

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Reply to
Christopher

Each LED needs a current-limiting resistor in series. 270 Ohms is a reasonable choice. That will give around 11mA into a typical 2V red LED ((5V-2V)/270R = 11mA).

If you don't use the entire 20mA to drive the LED, you'll have some left over to drive additional logic circuitry.

Reply to
Nobody

It doesn't need to be 'each' if (as seems likely) only one is lit at a time. A single resistor from GND to all-cathodes-together will work, as long as only one anode at a time is held high.

Reply to
whit3rd

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