[sdiy] 7-segment LED displays with 4511 driver chip - max current?

Gordonjcp gordonjcp at gjcp.net
Thu Aug 6 11:35:22 CEST 2015

On Wed, Aug 05, 2015 at 10:29:52PM +0200, Rick Jansen wrote:
> On 05/08/2015 19:34, Brian Willoughby wrote:
> >In the old days, a TTL chip like the SN74143 would drive up to 22 mA on each of its 7-segment driver outputs, and had what seems to be plenty of headroom since the chip could dissipate 1.4 W total. But that's an obsolete chip that only operated on a 5 V supply.
> >
> >I agree with Richie: handle the BCD conversion in your code, and wire the individual LED segments so that you can create any pattern you want. Even old product designs from the pre-surface-mount decade of the eighties had direct drivers for the LED segments to save money on parts like special BCD decoder chips. Have fun.
> The CD4511 is 30 euro*cents* at Conrad!
> The Arduino is not fast, and it *is* doing timing and interrupt
> stuff, so if I can offload the display of the numbers, which are
> just a nice extra, and not crucial, I don't mind doing that with
> three 30 cent chips.

Use shift registers.  These will latch the LED pins, allow you to display arbitrary symbols and only take up a couple of GPIOs.

Gordonjcp MM0YEQ

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