Dim Segment Display using 5461AS 4 digit 7 segment display

Projects Programming
1

Can anyone help with this problem I have operating a 5461AS 4 digit 7 segment display?

The problem is basically that all the A segments (i.e. the top horizontal) and, to a lessor extent, the first digit B segment (top right vertical) are extremely dim compared to all the other segments in the display when driven direct from my Arduino UNO using this sketch

#include "SevSeg.h"
SevSeg sevseg; 

void setup(){
  byte numDigits = 4;
  byte digitPins[] = {10, 11, 12, 13};
  byte segmentPins[] = {9, 2, 3, 5, 6, 8, 7, 4};

  bool resistorsOnSegments = true; 
  bool updateWithDelaysIn = true;
  byte hardwareConfig = COMMON_CATHODE; 
  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments);
  sevseg.setBrightness(90);
}

void loop(){
    sevseg.setNumber(8888, 3);
    sevseg.refreshDisplay(); 
}

and wired the attached (bad) drawing (each resistor is 680R)

I have tested each segment individually, both with a separate 5v power source and resistor and by modifying the sketch to just light the A segments. With the separate power supply, every segment checked out fine. Modifying the sketch by just driving the A segments improved things, but not by much. As soon as another segment is driven in addition to the A segment, it dims.

If I reassign segment A to a different Arduino pin, it makes no difference.

Am I drawing too much current from the Arduino? If so, why is it only segment A that is affected?

Any suggestions gratefully recieved!

IMG_20200216_171636.jpg

IMG_20200216_192808.jpg

2

You have resistors on digits, not segments as the code is configured for.

3

I did wonder about that Aarg, but here:

LINK

it says to set resistorsOnSegments to true when using multi digit displays. Not sure if that can be confirmed elsewhere though.
I did change the two booleans to false anyway, but its made no difference, those top bars are still extremely dim.

4

STDummy:
I did wonder about that Aarg, but here:

LINK

it says to set resistorsOnSegments to true when using multi digit displays. Not sure if that can be confirmed elsewhere though.
I did change the two booleans to false anyway, but its made no difference, those top bars are still extremely dim.

Yes, the software is configured correctly. The resistors are in the wrong place.

5

Ah, I see. Many thanks Aarg.
I'll need to rustle up some more resistors in the morning. I'll let you know how it goes.

6

Well, it looks like I must have a faulty display. Placing resistors on each segment makes no difference. I took a gamble and removed all resistors completely, and I still have dim A segments. I've tried new wiring just in case but it made no difference.
Ah well, order a new one.....

7

Did you try testing the display again manually? In your original post, you said that you confirmed it that way.

8

Yes I did go back and recheck each segment manually, and whereas its not as noticeable as when the UNO is driving the display, it seems the upper segments are dimmer after all, so I think its definitely a faulty display.

Thanks for the help though Aarg