Newbie, Trying to read a circuit Diagram

Discussion in 'General Electronics Chat' started by Wombat, Jul 5, 2007.

  1. Wombat

    Thread Starter New Member

    Jul 5, 2007
    I'm really more familiar with the software side of devices, so trying to dig through the hardware side is really testing my memory from college. So thanks in advance for any help you can give me. :)

    I'm trying to make a circuit that will fade several LEDs in and out. I found a circuit that does this over at BEAM Circuits named a Quad LED Fader (QLF). I've taken the circuit diagram:
    and tried to layout the components, but it has left me with a couple of questions.
    1) The input voltage listed is 3v-9v. LED5 seems to be in place to reduce the 9v supply for the 74HC14 - If I'm using a 3v supply, do I need this LED and/or the 1K-ohm resistor?
    2) Power seems to be wired to the 74HC14's Vcc pin (for obvious reasons) and then to pin 5 - but pin 6 is left open. Why is this connection made?

    Thanks again for your help.
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    1) The text says regulation is for stabilizing the frequencies of the relaxation oscillators. If you have a nice stable three volt supply, I'd eliminate the components. If you are using a battery instead, the frequencies might drift as the battery discharges. (Of course, a little extra randomness might not hurt.)

    2) That gate of the chip is not used. Input is tied to chip Vcc to keep things tidy. In "version five" of the circuit, pin five of the Schmitt trigger is tied to ground. You should be okay doing either.
  3. Wombat

    Thread Starter New Member

    Jul 5, 2007
    Thanks for helping me out. I was able to finish wiring up the circuit last night and it worked like a charm (first time out - damn I'm good :D).