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Cybernetic Data Products LED sign PS help please

slywuf

New Member
I have no experience with Arduino (yet) but was thinking that the existing shift registers probably were not essential. HOWEVER - keep in mind that there are 29 of these 5x7 LED matrix modules connected to the 12 trace buss on the display PCB that I mentioned. Going in and doing wiring surgery on all 29 modules, to access the 5 individual column pins on each module would be a real pain in the U-no-what.
That 12 trace buss is really easy to access on the board, so if that was used to interface the Arduino, major surgery can be avoided.
Can't the existing shift registers and hex digit drivers be retained?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I can only imagine he thought (for some strange reason) that you were only wanting a single matrix of LED's, which would indeed make the extra IC's rather pointless. However, for a number of arrays (as in your case of 29), using the existing logic chips and drivers is the only thing that makes sense.

Using an Arduino should make it fairly easy, it's vastly more powerful than the old 6502 system, and much more capable of the job.

So it's really a question of working out exactly what signals you need to provide for the CD4015's, and then programming the Arduino to provide it.

There's plenty of information about using the Arduino to feed shift registers, and libraries to do so - it shouldn't be too difficult to modify those examples.

https://www.arduino.cc/en/Tutorial/ShiftOut
 

MichaelaJoy

Active Member
I have no experience with Arduino (yet) but was thinking that the existing shift registers probably were not essential. HOWEVER - keep in mind that there are 29 of these 5x7 LED matrix modules connected to the 12 trace buss on the display PCB that I mentioned. Going in and doing wiring surgery on all 29 modules, to access the 5 individual column pins on each module would be a real pain in the U-no-what.
That 12 trace buss is really easy to access on the board, so if that was used to interface the Arduino, major surgery can be avoided.
Can't the existing shift registers and hex digit drivers be retained?
You couldn't use an Arduino by itself, unless it is a +5V device.
All of that logic is +5V, so you'd need level shifters for all outputs.

Yes you need to keep as much of the drive logic as possible.. You have to clock the states of the leds into the shift registers. When the row lines are strobed, the shift register bits will make the respective column leds light up. (I'm guessing '0': It lights up, '1': It's back-biased and it doesn't light up. It could be the opposite though.)

You'd probably need a 4049 to drive the shift register line clock. You only need one clock line (common for all shift registers),
but unless you do some kind of demultiplexing., you need a data line for each shift register.

That's not difficult to do.

1 of 16 decoder.jpg
 

NsrMagazin

Member
I can only imagine he thought (for some strange reason) that you were only wanting a single matrix of LED's, which would indeed make the extra IC's rather pointless. However, for a number of arrays (as in your case of 29), using the existing logic chips and drivers is the only thing that makes sense.

Using an Arduino should make it fairly easy, it's vastly more powerful than the old 6502 system, and much more capable of the job.

So it's really a question of working out exactly what signals you need to provide for the CD4015's, and then programming the Arduino to provide it.

There's plenty of information about using the Arduino to feed shift registers, and libraries to do so - it shouldn't be too difficult to modify those examples.

https://www.arduino.cc/en/Tutorial/ShiftOut
Yes, I am sorry I have to do a lot of things and answer other topics and other forums, also I am very busy at work.

EDIT:
Start testing the output of signals needed by connecting the pins to a power supply directly. The first thing you should decide is the number needed for activating 1 LED. It should be something in the form of "0bYYYYYYYYY.......". In hex "0x......".
 

Nigel Goodwin

Super Moderator
Most Helpful Member
You couldn't use an Arduino by itself, unless it is a +5V device.
All of that logic is +5V, so you'd need level shifters for all outputs.
When you don't even know what voltages standard Arduinos use, why post about it?.

Standard Arduinos (like the most popular Uno) are 5V, as is the 6502 of course.

Yes you need to keep as much of the drive logic as possible.. You have to clock the states of the leds into the shift registers. When the row lines are strobed, the shift register bits will make the respective column leds light up. (I'm guessing '0': It lights up, '1': It's back-biased and it doesn't light up. It could be the opposite though.)

You'd probably need a 4049 to drive the shift register line clock. You only need one clock line (common for all shift registers),
but unless you do some kind of demultiplexing., you need a data line for each shift register.
Presumably all the logic is already there, as this is a commercial piece of kit.
 

MichaelaJoy

Active Member
When you don't even know what voltages standard Arduinos use, why post about it?.

Standard Arduinos (like the most popular Uno) are 5V, as is the 6502 of course.

Presumably all the logic is already there, as this is a commercial piece of kit.
I stand corrected. The Arduino Uno is +5V. And since the OP was talking about having to tear out all of that logic, I advised against it.
 

rjenkinsgb

Active Member
I'd expect that all the shift registers are chained through, so an entire row of data can be loaded serially.
It's then displayed by activating the appropriate row driver.

And repeat for each row, in sequence, to display data over the full LED array.
 

slywuf

New Member
I appreciate the help and comments from you guys. Obviously, I need to figure out which end of an arduino is up and start doing
some testing with this old LED sign. I'll get going on that and report what I find.
 

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