4 Digit-7segment display-No resistors

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DJ-Dwayne
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Joined: Mon Sep 29, 2014 9:15 am

4 Digit-7segment display-No resistors

Post by DJ-Dwayne » Thu Jan 07, 2016 10:49 am

Image
Please note....I've suffered A.D.D. all my life. So although this project may seem "basic" in some ppls minds, it's taken me years to complete these two pictured projects and it's very hard for me to even type out this post. So please be gentle with any comments :oops:

Pictured are 2 boards. The one on the left was my first board/attempt. Only three digits. It's basically a 3x8 matrix display so only 1 segment anywhere is lit at any one time resulting in an approximate max LED current draw of about 25ma at any one time. It uses 3 transistors and 3 resistors to work. (Other resistors & button shown are non essential). I thought that it was pretty clever but soon released it was a bad board design as it uses digital pins 0&1 so I couldn't do any serial comms with my PC. And I also wanted to try to expand it up to 4 digits.

So along came the 2nd board.

It's basically a 4x8 matrix display so only 1 segment anywhere is lit at any one time resulting in an approximate max LED current draw of only 25ma at any one time. It uses NO resistors or transistors. Current regulation is controlled via PWM on each of the digits common cathodes. (Which I thought was a very clever idea). I'm working on code to be able to digitally control the brightness of the whole display if need be.
Any flickering can be programmed out via the use of PWM. Which is handy because as I add more code, it affects the timing therefore adding more flicker.

My longterm plan is to have a 0 - 30v auto ranging voltmetre which also displays on my PC screen (need to learn PC programming :? )

The problem I have is that I need to push things aside for several weeks at a time to rest this f###ed up mind of mine. Then when I do come back to it, I've gotta try to remember what i've done. Very frustrating. ARRRGH!!!!

andrew
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Re: 4 Digit-7segment display-No resistors

Post by andrew » Sun Jan 10, 2016 9:25 pm

Well done, and thank you for sharing that with us.
:)

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