I have come across another one of these clocks: http://www.dougswordclock.com/kits.html It looks like he uses 117 LEDs, but maybe he lights up words rather than single letters, couldn't really tell.
One way of doing it with a single chip is by pulsing the leds for a very short time with a very high current (say 1A for 150us), then you run through all the leds only turning the ones on that need to be on. This way, you cover them all within 20ms, so you can do that 50 times per second without a noticeable flicker and it won't matter how many are light up at anyone time. The average current through the LED is then 7.8mA which is quite good when using high efficiency LEDs. If you go further into that, you can take as a reference not the 128 leds in total, but the maximum of leds that are turned on at anyone time. Suppose that is like 32 leds or something, you can then go to 600us pulses and increase the average current to about 30mA. Of course you can only do that if that is still within the specs of the leds. Michel On Feb 1, 6:26 am, Quixotic Nixotic <[email protected]> wrote: > On 31 Jan 2012, at 18:26, Nicholas Stock wrote: > > > Gang, I know this isn't nixie related, but I thought I'd bring it > > to your attention as we're all clock enthusiasts... > > >http://www.kickstarter.com/projects/252714519/clockthree-jr > > > I've built one already and as a Word Clock it's pretty sweet. > > I think it's doable with a single chip. I have successfully > charlieplexed a single chip clock with 144 LEDs and this clock only > needs 128. The issue would be how many LEDs are to be lit at any one > time, to ensure the refresh rate is flicker-free. I might have to > have a go at this after a few other projects have seen daylight. > > John S -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
