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LED Mini Signboard PIC 16F628A

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Gayan Soyza

Active Member
Here is a present for Mike K8LH because of his help giving to signboard lovers.

This project Named LED mini signboard.


*User define message (String length = 30 letters including spaces)
*50 different characters = A-Z, 0-9 & special characters
*Battery power operation 3.6V-4.8V

This is the smallest signboard I have ever made. The nice thing with this design is you can write your own message using its two buttons.

Saving is pretty simple

Press & hold the “Select” button at anytime. It will show you letter “A”. Now release the button. At each press the “Select” button it will shift to next character.
Press “Save” button to mark the selected letter. Likewise make a sentence by the two buttons & after completing press & hold the “Save” button for 4 seconds so it will save the whole sentence in the memory. Release the button now it will scroll the message nicely that you saved.

Supportable characters


1, 2, 3, 4, 5, 6, 7, 8, 9

“/” “%” “Heart” “Face” “-““=” “Comma” “Arrow” “+” “:” “Dot” “(““)””Degree”

For additional details visit my blog


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Great project. I want to build it but can I substitute the uln 2003-darlington array with something else as I cant obtain one of these yet.
Thanks alot for letting us build it I can wait to test it.
Gayan, does your scrolling routine use any form of double / triple buffering? I had fiddled with a single character sign some time ago, and while scrolling static messages was easy, I ran into a mental road block in regards to code for scrolling dynamic messages, such as the time and date. Feature creep eventually killed my interest in the project - the trouble with adding too many bells and whistles.

**broken link removed**

blog post:
justDIY Project Log LED Sign has a purpose!
Hi justDIY there are five display column registers.But all the code is done with another five of working registers.At the end of the each display frame I'm loading working registers to the column registers.

Actually this project a bit hard & gets lengthier. The secret is withing the offset values to the table patterns :D

I see your project too that's bravo sir.
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Gayan, can you put the .asm file on the forum as your website has absolutley no information on the LED Mini Signboard PIC 16F628A Project.
Hi Gayan,

What do you think about this design for Cathode row 5x7 displays? Perhaps a Clock/Calendar/Alarm/Timer/Sign project? And since the 74HC595 column drivers can 'sink' or 'source' you could use the same design for Anode row displays just by swapping out the N-FET 'sinking' row drivers with P-FET 'sourcing' drivers (and a minor software change).

Regards, Mike


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Very nice sir.But I'm scared with your macMUX design its a bit complicated for me :D I'll show a similar design I recently did like your last diagram.But I did by cascading the shift registers using the QH' pins.
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I would connect all the 595s the dame way you have it but use 1 more to control all the OE lines. And have all serial data on 1 pin. This way i can shift data to the 595 to select the first (last) 595 and then send that data...

let me make a schematic. It wont* be as pretty as mikes tho heh


Too lazy right now lol ill do it later on
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Hi Gayan,

It's really very simple and it takes less time to send 56 bits of data for each row scan than it would for daisy-chained shift registers. If you're interested at all please let me know and I'll do a little write up to explain how it works. Once you understand how it works it's really quite intuitive.

Regards, Mike
Connecting few Dot Matrix blocks and show some words or clock isn't that hard.
How about using dedicated display drivers. Like HOLTEK chips, MAX Ics & etc. It can reduce the MCU display driving load. That is a big saving right ! And also those chips hv some cool options like Display Dimming, Display Blinking, blah.blah....

Don't you think because of that saving we can do much more things with our MCUs ?

Plz correct me if im wrong.
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Here is another design of mine.The hardware is similar to your method with some minor changes in column driving side.

I cannot resist I want to show.

YouTube - Sign Large

Mike I like that "Micro Application Consultants" title


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