I've got eight 7-segment displays. I know I've multiplex four at once but eight seems like a lot. It'd be slick to need just 16 pins. Can it be done?
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I've got eight 7-segment displays. I know I've multiplex four at once but eight seems like a lot. It'd be slick to need just 16 pins. Can it be done?
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Yes.
-- Grant Edwards grante Yow! An Italian is COMBING at his hair in suburban DES
Of course. Here's one for 16 digits:
but
If you are looking for dedicated hardware also look at the ICM7218. It w2as made by both Intersil and Maxim, but today...
If you are trying to do this as a roll your own- look up "charlieplexing" on the Maxim web site and also EDN and Electronic Design. There was a flurry of discussions recently and how to use the least number of bits.
I have a very old HP application book on optoelectronics (in electronic format) that discusses this quite well. if you let me have an address, I can try and figure out how to get the 120MB to you.
-Aubrey
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w2as
You may want to check AN1216 and Application Brief D-0004 from Avago.
-Aubrey
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pay attention to the peak current specs on the leds and whatever you're using to drive 'em vs. the peak current needed to get the brightness you want.
Depends on what sort of intensity/brightness you want from them.
8-way mux was commonplace many years ago to economize on hardware. Often, the display multiplexing hardware was tied to the *keyboard* multiplexing (e.g., drive a display digit and a keyboard column at the same time).Look at the efficiency of your displays (i.e., how little current does it take to get the brightness you want) and the maximum current each digit can tolerate (before it becomes a DED -- Darkness Emitting Diode).
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