2009-05-24

Ye Olde Output Indicator - LED Array

Somewhere along the line after pushing your current limiting resistors into the solderless breadboard for about the five millionth time, and then reaching for the mini-needlenose pliers to straighten the leads for an accumulated about half as many times...

You get to thinking, "there's got to be a better way". Yeah, sure 1k resistors are cheap, but that's not the point.

So in looking over at the parts bin, I noticed a hand full of green and red 3mm LEDs from some forgotten project from a decade ago, the typical yellow of some resistor network chips on a failed piece of Cisco routing equipment and had a "Eureka!" moment. These items, and a 1 inch square proto board I'd just purchased plus a 90 degree header pin strip could relieve me from the bent lead annoyance and free up time to mess with trying to burn out expensive sensors while seeing if the programming logic comes anywhere near driving the eventual motor controller board correctly.

The proto board had nine holes along one edge, so we can get a whole byte's worth of flashing digital goodness. And here's the result.


Equipment List:
  • RN1 - 1k isolated 16 pin DIP resistor network
  • LED1-8 8 red or green 3mm LEDs
  • 90 degree header pins, snap off 9
  • 1 inch square MExplorer proto board
The array is wired for common cathode, pin high drives the LED on. Now getting one or more LEDs into operation is just a simple push of the array into the breadboard, a jumper wire for ground, one for each LED to activate and you're up and running.

I've been using these with the BoArduino, so I make them in pairs and on one, swap the end the common cathode pin is on. This allows the LEDs to face in the same direction when the boards are plugged in on the digital pins.

And here's a schematic.

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