how to interface a digital IC with an LED

[panfilero]

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

 

[Christopher]

On Sun, 22 Mar 2009 15:14:00 -0700 (PDT), panfilero
<panfilero@gmail.com> wrote:

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

For $6 this might work for you.

http://www.electronics123.com/s.nl/it.A/id.2483/.f


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


Kind of makes me miss good old Heathkit!!!

* * * *

Christopher

Temecula CA.USA
http://www.oldtemecula.com

 

[Nobody]

On Sun, 22 Mar 2009 15:14:00 -0700, panfilero wrote:

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?

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).

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...

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

 

[whit3rd]

On Mar 22, 4:09 pm, Nobody <nob...@nowhere.com> wrote:

On Sun, 22 Mar 2009 15:14:00 -0700, panfilero wrote:
Hello, I would like to hook up LEDs to a decoder [HC series CMOS/5V]

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

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.