Thursday, July 21, 2016

Let's introduce our little friend; Little Mr Duty Cycle

Forgot all about the LED's being duty cycled while being multiplexed.

8 rows active (~12.5% duty cycle):
1) 12.5% duty cycle, quite dim, but still alright with LED's. Incandescent bulbs barely light up.


1 row active (100% duty cycle):
2) 100% duty cycle. Everything works peachy, including incandescent bulbs.

When all rows are active the voltage is roughly 1.2V, thanks to the ghosting - otherwise it would be lower. This is with 5V input. To get it as bright as it should be I think I'd need to go up to 30-48V for 5V actually, which requires separating the logic chain voltage from the drive voltage. 

And even weirder - the LED doesn't light up much at all when using the 12V line, so it looks like something is wrong there (probably programmatically, as that row requires special handling etc).

Welcome to nightmareland. :/

1 comment:

  1. You've got this mate, compared to the coding stuff you have been through this will be a piece of cake :)

    There must be a stack of example circuits online that you can compare against yours, even if the code is going be different. Good luck!

    Cheers,
    Shaz

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