Re: 300 mA from a microcontroller pin

rickman:

There you go. Arlet said there might be alternate solutions and there
is one. You don't need the tri-state control. You can drive the LED
forward with one pin high and the other low, backward by switching the
two and off by bringing them both high or both low. Can't be much
easier than that! You will still need two pins from your controller,
but you don't need a complex driver circuit.


Thanks for your suggestion, but the second pin of the LED package
will go to a shift register. I'll try explain:

I have a grid of LED's, 7 x 6. In each column, the second leg of each
LED package will be common, and they will go to a pin on a shift
register. In each row, the first leg of each LED package will be common,
and it will come from the microcontroller. I shift a 1 across the shift
register to determine which column will light. The shift register pins
provide either 5 V or 0 V, but I have a transistor setup whereby they
provide either 5 V or high impedance.

I'll post a picture of the relevant part of the circuit now in a few
minutes.

--
Tomás Ó hÉilidhe
.

Relevant Pages

  • Re: Just one pin to control a shift register
    ... My design might not be brilliant, but I hope it will work in the end. ... Jumper a pin from the PIC to the SR so that you clock it properly. ... The first pin would go to the actual shift register ...
    (comp.arch.embedded)
  • Re: Loss of synchronisation: Are the chips reliable?
    ... My college project this year was to make a Connect4 game consisting of ... Reset the shift register to all zeroes ... The method of using one pin would be implemented by feeding the ...
    (comp.arch.embedded)
  • Single pin to control a shift register
    ... I have an 8-Bit shift register chip, and at any time there will only ... Each shift-register pin will go to a single LED, ... micrcontroller boots up, I would put a HIGH onto the input, clock it, ... On the input to the shift register, I put an OR gate. ...
    (comp.arch.embedded)
  • Just one pin to control a shift register
    ... I have an 8-Bit shift register chip, and at any time there will only ... Each shift-register pin will go to a single LED, ... micrcontroller boots up, I would put a HIGH onto the input, clock it, ... On the input to the shift register, I put an OR gate. ...
    (comp.arch.embedded)
  • Re: Controlling hundreds of LEDs
    ... >(and does this work based on the clock pin, and not the latch?) So if I ... >I get 16 unique outputs, which I can then redraw before the next latch? ... If you've got an 8-bit shift register, what happens when you shift in the 9th ... SQ8 pin on the '595 is where you either put the bit bucket or you put ...
    (sci.electronics.basics)