Sunday, November 20, 2011

General Practices in Building Your Lunetta

General practices with the ics you use:
  • connect a small cap (0.1uF ceramic) between the power pin and ground on each cmos chip (think of it as a little energy bottle for the ic)
  • place 100k resistors between input and ground
  • super important:  Tie all unused inputs to ground  (in some cases, an unused input needs to connect to the power supply to have a function work on the ic)
  • LEDs:  If you're using leds, just attach them to the outs of your ics and connect them to a resistor to ground (I use Superbrights and use 10k resistors on mine)
  • work with small perf boards/strip boards instead of 1 large one (easy to debug)
  • try to use color coded wire to aid in building each module (red for power, black for OUT, green for IN for example)
We place a resistor on all inputs and have them reference to ground because we want stability.  Cmos chips are sensitive little buggers when their inputs are left floating. Our lunettas are patching machines at heart, so when an ic's input isn't being connected to anything, we want to bring that input LOW through the resistor that's referencing ground.  I mention 100k resistors because I am a creature of habit, but I've had great results even using resistors as low as 22k.

The little cap between the power pin and ground helps ensure each ic in your lunetta gets enough "juice" to work its magic.  I generally add a larger cap as well between the power rail and ground when I occasionally use larger perf boards.

A 0.1uF cap between the power pin and Ground ensures that chip has spare power.

In the photo above, I did not use both halves of the 4015 to aid in clarity.  The data sheet will show you which pins are for power, ground, outs, etc.  In this case, power needs to connect to pin 16 and pin 8 goes to ground.

1 comment:

  1. I am just starting making CMOS Noise. This post is very helpful. Thank you.