Steve2381
Senior Member
Hey all.
I have a complicated circuit. Basics... 40x2 running a Max7219. This Multiplexes 60 leds inside illuminated buttons.
I have tried to keep the MAX7219 near the IC, but it wasn't possible to have it on the same PCB. So its about 10" away, with its data lines run in a screened cable.
As the leds are spread over a control panel. obviously the outputs of the Max7219 are wired over a larger area. However I don't think that particularly causes an issue (well I hope not).
I always seem to run into trouble with supply noise. The Max7219 is randomly either illuminating all the leds, or sometimes they drop out. Other times they work fine.
The entire panel worked fine for weeks on the bench (off a dedicated bench supply), but now its playing up once installed.
There was a HC-05 bluetooth module in circuit, and they are notoriously noisy so I have removed that for now.
I am running the project off a new 70w computer PSU. I thought that would give me a nice high quality supply. Apparently not. It is showing a nice 5.12v consistently.
Got the usual 0.1uf and 100uf across the chips. What else can I do? I am pretty sure its supply noise or noise on the data lines.
Is there any way of protecting the data lines = CLK, DIN and LOAD? Can any of these be pulled high/low? Would that help?
I also considered ferrite beads, but I believe you need to work out the correct value, and I don't have a scope.
Any suggestions would be immensely appreciated.
I have a complicated circuit. Basics... 40x2 running a Max7219. This Multiplexes 60 leds inside illuminated buttons.
I have tried to keep the MAX7219 near the IC, but it wasn't possible to have it on the same PCB. So its about 10" away, with its data lines run in a screened cable.
As the leds are spread over a control panel. obviously the outputs of the Max7219 are wired over a larger area. However I don't think that particularly causes an issue (well I hope not).
I always seem to run into trouble with supply noise. The Max7219 is randomly either illuminating all the leds, or sometimes they drop out. Other times they work fine.
The entire panel worked fine for weeks on the bench (off a dedicated bench supply), but now its playing up once installed.
There was a HC-05 bluetooth module in circuit, and they are notoriously noisy so I have removed that for now.
I am running the project off a new 70w computer PSU. I thought that would give me a nice high quality supply. Apparently not. It is showing a nice 5.12v consistently.
Got the usual 0.1uf and 100uf across the chips. What else can I do? I am pretty sure its supply noise or noise on the data lines.
Is there any way of protecting the data lines = CLK, DIN and LOAD? Can any of these be pulled high/low? Would that help?
I also considered ferrite beads, but I believe you need to work out the correct value, and I don't have a scope.
Any suggestions would be immensely appreciated.