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Topic: Having trouble controlling 3 Row Seven Segment with 4 shift register 74hc595 (Read 3664 times) previous topic - next topic

zifank

Hello,

If anyone could give me some advise or example code that would be great.

I am using a custom 16 digit seven segment with 4 shift register 74hc595 for 3 rows


I am having trouble with the controlling each digits.

Thank you for your help!

ieee488

You built the PCB before you verified that your circuit would work?

zifank

no.
I bought it, at online store 3 months ago, the seller does not provide complete data sheets and the libraries. please give me solution.

zifank


ieee488


PaulRB




You should contact the vendor. If they do not have any code, perhaps they will have a data sheet or at least a schematic.

Can you see any codes/part numbers on the sides of the digits? Or the transistors?

I should warn you, it looks like it was designed by someone who is not very expert. There are no bypass caps for the chips, for example, and no reservoir caps. These could be added, if you can solder reasonably well.

zifank

thanks @PaulRB for ur respon. maybe this is custom part or clone from original modul.


can you give me a sample code for controling a multi seven segment 7 digit?

PaulRB

can you give me a sample code for controling a multi seven segment 7 digit?
Yes, I could easily give you some example code. But it would be pointless. I know it would not work. Code has to be written to exactly match the hardware. I have never seen your hardware before.

If you can get no help from the seller, you can do some "reverse engineering". Identify the components from their part numbers. Trace the tracks on the PCB. Make your own schematic diagram. From that, you can write some code. We can help with some stages of that process. But you have to start, because you have the hardware in front of you.

Looking closely at the board, this is what I believe I can see and guess. There are 4 chips. It would make sense if they are 74xx595 shift registers as you say. The chip closet to the connector drives 6 transistors which in turn drive the commons for the digits in that column. The other 3 shift registers drive the segments for the digits in the 3 rows, via current limiting resistors. The 4 shift registers must be "daisy-chained", given there are only 5 pins on the connector, including power and ground. I would guess that S=Serial data, C=Clock and R=latch.

The code must perform the multiplexing, sending 3 bytes of segment data and 1 byte to select the digit column, and lighting one column of digits at a time. The most important answers you need to find out, I believe, are the digits common anode or common cathode and are the transistors NPN or PNP (or are they FETs). The part numbers written on the displays and transistors may help answer those questions.

zifank

you are the the "rock" master @PaulRB, u bright my day... :)

the digits as common cathode, the transistor is PNP

PaulRB

the digits as common cathode, the transistor is PNP
Are you sure? How do you know? The transistors appear to be connected to the digit common pins. If the digits are common cathode, I would have expected NPN transistors. For common anode, I would expect PNP.

zifank

i test one transistor with multimeter, and the result is PNP, but for the digits i'm not sure.

zifank


PaulRB

And two LEDs per segment. Do you know what colour the LEDs are? I wonder if a 5V supply will be enough.

zifank


PaulRB

i used 9volt supply
Used it for what? You could damage components by applying too high a voltage. What kind of 9V supply did you use and what was the result?

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