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 Forum index » DIY Hardware and Software » Arduino
7 Segment Display Problem
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bubzy



Joined: Oct 27, 2010
Posts: 555
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PostPosted: Thu Aug 30, 2012 1:04 pm    Post subject: 7 Segment Display Problem Reply with quote  Mark this post and the followings unread

So, im building a bpm thingy for my modular and wanted to use 3, 7 segment displays to display the bpm (i thought a 16x2 lcd display would be tacky)

it took some time, and some learning (thanks edisonrex)
but i finally came up with this.... hope it helps someone out sometime.

sorry for my messy code, its something ill probably never stop doing.

youtube vid here too
http://www.youtube.com/watch?v=aLDGO7JDEeQ&list=UUBty83q-zxoOXa0h0UfLGCg&index=1&feature=plcp

please ask any questions and offer any suggestions Smile


EDIT : updated to use 3 pins from arduino (including reset)


arduino 7 seg 2 pins.bmp
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 Filename:  arduino 7 seg 2 pins.bmp
 Filesize:  390.53 KB
 Downloaded:  100 Time(s)


_7_seg_2_pins.txt
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 Filename:  _7_seg_2_pins.txt
 Filesize:  1.46 KB
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Last edited by bubzy on Sat Sep 01, 2012 5:59 am; edited 1 time in total
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elmegil



Joined: Mar 20, 2012
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PostPosted: Thu Aug 30, 2012 2:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

So.... A BPM thingy?

If you want the arduino to simply display a BPM value, there are 7 segment driver chips (usually BCD input, like http://www.play.com.br/datasheet/CD4511.pdf) and I believe an Arduino library to drive them. It looks to me like this particular application is just testing the LCDs by displaying a upward count, is that right?

I'm just trying to get the connection between what you describe and what I see Smile
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bubzy



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PostPosted: Thu Aug 30, 2012 2:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

ouch!
thats a lot of pins Razz
this is just the start and yes this just tests the 7 seg displays Smile
i think running 21 leds off 5 pins is pretty good efficiency

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elmegil



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PostPosted: Thu Aug 30, 2012 4:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

It's a latch, so you only need one set of 4 pins (one BCD digit) and a selection method to drive any number of displays. For 3 digits, I'd use two more bits and some logic to select which driver chip I wanted to update. You do need one driver per digit, so the chip count can climb... But I could do 28 LEDs with those 6 pins Very Happy

But it's just one thing or another, there are always many ways to do this stuff. Not trying to argue with you, it was just the way i would have done it.
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bubzy



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PostPosted: Thu Aug 30, 2012 5:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Of course Wink
There's actually a way of using 2 pins with these chips as pointed out by blue hell in the chat earlier, but of course it's all personal preference. I used what I had to hand and learned about shift registers. I don't do arguing Smile everyone has their own opinion and their own methods, that's the beauty of this site, and this hobby Smile

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bubzy



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PostPosted: Sun Sep 02, 2012 3:19 am    Post subject: Reply with quote  Mark this post and the followings unread

dont forget a resistor to ground off the 7 seg displays Very Happy
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bubzy



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PostPosted: Sun Sep 02, 2012 3:37 am    Post subject: Reply with quote  Mark this post and the followings unread

PCB layouts here, they are a bit scrappy and currently untested, but im gonna etch and test these today.

apologies for my amateur designs Smile

as its single sided, i couldnt find a good way of routing all of the led's together, thus the layout, im going to put the 7 segs on perf and wire them from the holes on this layout.

edit: new version uploaded, messed up pins 9 and 10


7segpcb.zip
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Mdashdotdashn



Joined: Aug 21, 2012
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PostPosted: Mon Sep 03, 2012 8:21 am    Post subject: Reply with quote  Mark this post and the followings unread

If you want to use a ready-made display (although it might be less fun), check out

http://www.adafruit.com/products/772

Uses only 2 pins. I'm using it together with a MIDIvox and it works quite well.

Cheers
Marc.
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bubzy



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PostPosted: Mon Sep 03, 2012 1:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

i intentionally steered away from those displays on this project Smile although i have used the lcds on other projects Smile
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