/diy/ - Do It Yourself

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Anonymous Sat Jul 22 20:12:15 2017 No.1214162 [Reply] [Original]

Have any of you tried to use custom, multiple digit 7 segment dynamic displays with microcontrolers?
I want to replace control board of dead coffee machine which uses one of them. It has 4 seven segment digits, 'clock', 'timer' and colon. 4/12 legs are marked with black dots, so I assume it has 4 backplanes. Apparently all I need to do is figure out what symbol is on what backplane and find some way to get three different voltage levels from atmega .
http://www.dataweek.co.za/article.aspx?pklArticleId=2382&pklCategoryId=31
What's the best way to do it?

>>	Anonymous Sat Jul 22 20:14:02 2017 No.1214164 File: 9 KB, 702x533, display.png [View same] [iqdb] [saucenao] [google] >>1214162 Layout of original board looks a similar to fig 8 from the article.

Anonymous Sat Jul 22 21:04:53 2017 No.1214189
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>>1214162
No, never.

From what you're describing it sounds like a multiplexed LCD.

You're not going to be able to get that many voltages from an Atmega. You're going to need to step down/up whatever your source voltage is.

To control your LCD you're probably going to want to use a driver with a built in shift register. Sounds like you have 12 pins, so get something with a 12 bit shift register.

>>	Anonymous Sat Jul 22 21:25:06 2017 No.1214200 >>1214162 many manufacturers make driver ics specifically for driving various numerical displays of all types you could care to name. don't reinvent the wheel.

Anonymous Sat Jul 22 21:48:03 2017 No.1214213
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>>1214200
the problem is, my LCD is marked as CM4196t which probably stands for chinese control board of my coffee maker and I can't find anything about it.
I'm also thinking about designing my own board for cheap calculators and selling them as school cheating machines.

Anonymous Sat Jul 22 22:30:10 2017 No.1214238
File: 21 KB, 899x439, Przechwytywanie.png [View same] [iqdb] [saucenao] [google]

I just figured that I can increase voltage on each backplane node by switching on internal pull-up.
Assuming they are about 40k, with 12k external pull-up and 12k external pull-down I get three levels:
low (0V) with PORTCx == 0, DDRCx == 1
middle (2.5V) with PORTCx == 0, DDRCx == 0
high (5V) with PORTCx == 1, DDRCx == 1.

>>	Anonymous Sun Jul 23 16:12:09 2017 No.1214602 File: 17 KB, 900x546, schematics are a language.gif [View same] [iqdb] [saucenao] [google] >>1214164 schematics are a language. please dont speak it like a retard; strive for clarity.

>>	Anonymous Sun Jul 23 20:22:51 2017 No.1214806 >>1214238 For pullup on you want PORTCx = 1.

>>	Anonymous Sun Jul 23 20:33:21 2017 No.1214819 >>1214162 What kind of coffee maker measures microsievert per centimeter

>>	Anonymous Sun Jul 23 21:45:40 2017 No.1214871 >>1214819 Japanese ones, obviously.

Anonymous Sun Jul 23 22:10:27 2017 No.1214891

>>1214871
>the cesium, it burns

>>1214162
Some PIC and AVR microcontrollers have LCD segment drivers built-in. Consider one of those, or at least read the hell out of the datasheets and app notes so you understand what sort of waveforms you'll want to drive them with.

Anonymous Mon Jul 24 14:32:42 2017 No.1215294

>>1214213
That's the coffee model. Number.

If you can't find a stamp on the icon it's proprietary and you'll have to reverse engineer it.

If you don't know how to do that i suggest you just get a screen that fits and is OLED. Then draw what you want with your own control board.

If all you care about is that LCD, call the manufacturer cause it's not easy getting one painted like that. That's not just 7 segment. It's proprietary and custom.

Anonymous Mon Jul 24 19:30:26 2017 No.1215504
File: 18 KB, 899x546, schemat.png [View same] [iqdb] [saucenao] [google]

My three state voltage seems to work, I can display single segments on it. I will post video in a sec.
>>1215294
It's Russel Hobbs 19590-56. Looks like branded chinese device.
>>1214602
ok, I fixed it.
>>1214238

>>	Anonymous Mon Jul 24 20:29:08 2017 No.1215540 File: 2.14 MB, 480x270, 20170724_235209 (convert-video-online.com).webm [View same] [iqdb] [saucenao] [google] >>1214891 >>1215294 I don't really want to spend too much money on this project desu. Webm shows looping throu all the backplane 1 values.

>>	Anonymous Mon Jul 24 20:43:47 2017 No.1215551 >>1215540 Bretty gud. Are you driving them with ac? If not, you can damage the segments. See http://ww1.microchip.com/downloads/en/AppNotes/doc8103.pdf

>>	Anonymous Mon Jul 24 21:11:06 2017 No.1215567 >>1215551 I'm not sure what do you mean by driving them with AC. Interrupting and changing state of backplanes? at My code is quite similar. https://pastebin.com/EftZppzj

>>	Anonymous Tue Jul 25 01:29:44 2017 No.1215666 File: 112 KB, 316x400, 1493600708523.png [View same] [iqdb] [saucenao] [google] >>1215567 Berry gud. The only suggestion I could make is to run your complement state right after your true state but I'm not even sure that matters. Cheers!

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