So I built my first 444 led cube with 2 74HC595 shift registers without thinking about that those ICs are not suitable for such task. Now I am looking for alternatives because one column is not lighting properly up (not enough power I guess).
NB! I really do not want to resolder anything on that project since everthing is pretty tight up on a small board and I really dont want waste any time on desoldering and on anything on that project beside replacing shift registers and testing if anything changed...
Are there any shift register with the same layout/pinout as 74HC595 that I can replace that provide more current for leds?
You see that one column has the top led working at max brighness but leds below that one does not light up at all. I thought that there is some bad connection but it does not seem so.
Somehow I don't think the shift register could be causing that fault.
Could that led at the top of the faulty column be soldered in the wrong way around? Anode and cathode reversed. It might have been manufactured like that.
Hi! So I was testing this column without full circuit turn on (with battery) and I noticed that while giving power to that column leds all other leds on that plane turn on as well. What does that mean? Other column leds does not behave like that.
Made a video to illustrate that situation. Thanks!
Okay scratch that last thought cause I found some other columns that act like that as well, guess it is because of how those leds are connected. But still polarity of those faulty column leds seems right as you can see from this video.
Ah, so now we are drilling down into yet another XY problem.
OK, now we clearly have a clear fault; the question is - is it software, or hardware - or somehow both? Switch to Sherlock mode.
Well, analysing that video, I note you turn the power on and all LEDs flash (except perhaps the one that doesn't which we cannot see), but the troublesome one flashes brightly. Before I go further, I am going to say that this almost certainly suggests that the fault is not in the code. Mind you, we have not been offered to see the code, which is generally an essential part of the process.
So I need to look at your circuit again to figure out what wiring mistake could possibly cause this fault at one point in a two dimensional matrix.
I note whilst writing this, that you have made further investigations.
While measuring leds resistance on 200 ohm mode with my multimeter I noticed that that faulty column leds does not light up slightly while other leds do. Maybe that indicate something? Dont know how is that possible since with batteyr they do light up...?
OK, so the only thing that is notable from your second video, is that when you energise the troublesome LED, two LEDs on your Nano illuminate as well. Now I would expect that if you were using "pin 13" (the unlucky pin ), that this might have some bearing as the indicator LED is directly connected to that pin, but your circuit diagram indicates that it is not used, so what is happening is purely related to a wiring fault or damage to the 74HC595s. The trick is to cross-reference and locate the fault.
Now allowing for loss of 0.5 V in the transistor and 3 V for a blue LED, 1.5 V over 100 Ohms is 15 mA and we would have to say, excessive for a 74HC595 when most or all of the outputs are turned on. Your multiplex ratio is only 1 in 8, so the LEDs are only "seeing" and average of less than 2 mA but with all LEDs on, each 74HC595 output is seeing that 15 mA all the time.
But your schematic indicates you are not using pin 13. So you are using a completely different wiring pattern then? And you have a solder blob where it should not be?
Oh yes, it's a Baite Pro Mini. But that should not affect anything. There is a 74HC595 between the Arduino and the display; you cannot feed back through that; it is the "parasitic" or protection diodes that cause this and cause other LEDs to light.
No, I can't figure it. I think you are going to have to replace that LED, carefully preserving it for forensic analysis - you do have a solder sucker, don't you?
Yes, you are using an odd version of the circuit. Well then, I'm off to bed.
), that this might have some bearing as the indicator LED is directly connected to that pin, but your circuit diagram indicates that it is not used, so what is happening is purely related to a wiring fault or damage to the 74HC595s. The trick is to cross-reference and locate the fault.