Hi,
I am using a Maker Focus 5V - 8 digit-7-Segment display using a MAX7219 in an arcade I'm making. The problem I am having is that after 10-12 seconds, the display shuts off. I tried placing a .33 uF cap across the power supply, same thing. I tried placing a 330 ohm resistor in series with the display, no good.
I then adjusted the 5vdc supply from 5.0 to 4.5v, but still shuts down. If I raise the voltage to 5.4, it stays off
Originally I was experiencing interference when I operated a small 12VDC motor, so I ran all wiring to the display in a 2 wire shielded cable for the 5V, and a 3 wire shielded cable for the signal wires. I made sure to ground only one end of the cable. The interference seems to have gone away , but I now have this shutdown problem. I tried swapping displays, no good.
I also tried a filter circuit I found on the internet using a 100uF electrolytic, a 200 uF electrolytic with a 10 ohm resistor in series between them.
Does anyone have a suggestion as to what is happening?
I keep a meter on the 5VDC and there is little flucuation. (less than 1 volt).
that’s a lot, try changing power supply for a more stable one
Not without a proper description - with diagram and preferably a clear photograph - of what you are actually doing. 
Please, post your sketch so that we can check that you have intialized the MAX7219 properly.
ARCADE NANO_FORUM Model (1).pdf (274.6 KB)
ARCADE SCOREBD_V1.pdf (16.1 KB)
Here are both the sketch and the portion of the nano & led wiring.
Read the forum guidelines. Post your test code in code tags. Use the IDE autoformat tool (ctrl-t or Tools, Auto Format) to indent the code for readability before posting code.
Why you have +5A (what does it even mean?) and it is connected to Nano VIN and also has a capacitor to +5V?
The schematic is a bit confusing - what exactly is the purpose of the relays? Is there a 2nd nano somewhere?
".pdf" is not a suitable image format.
That's the supply drooping far too much. 0.05V variation is more what you should tolerate. Either the supply or the wiring isn't up to it. Is a regulator over-heating and shutting down perhaps?
Huh?
Well, two things.
One is that it does not embed in HTML as an image, making it less than useful for this forum.
But it is not an image format. You can embed images in it in various image formats and the PDF "reader" will display them'; in fact this is frequently deliberately done to obfuscate documents to render them unable to have data extracted. A "proper" PDF can be edited and text cut and pasted, but if it is merely an image of a printout inserted in a PDF, the text (data) cannot be recovered.
Yes, one Nano is for the scoreboard display and one is for a 8 X 8- 4 in 1 Dot Matrix display.
The terminal strip is connected to outputs from a micro PLC (5V output). The relay contacts send 5V to the corresponding Nano pins.
The +5A terminal is just a wire number. It is a switched +5V through the START relay. I should mention, that the matrix works well, but sometimes the display loses the alphanumeric readout and all LED's for all sections light up, and I need to reset it. Not sure if the power problem is affecting both the Matrix and the scoreboard.
I am using a terminal board adapter for the Nano, and I noticed the LED light on the Nano went off once or twice, and when my finger touched the shell (housing) for the PWR connector, the light went back on. I ordered another terminal adapter, because I suspect there may be a defect, or loose connection causing the Nano to lose power.
But I cannot explain why the display cuts out every 10 - 12 seconds consistantly.
I also powered the scoreboard, did not operate any of the controls (relays, switches, motors etc.) and still, the display shuts down.
Otherwise, the sequence of operation works as it should.
it is because you connected +5V to VIN which on Nano has additional voltage regulator, so 5V becomes 3.8V or even less, and Nano is 5V board. you are under powering it.
Thanks killzone_kid. That makes sense. I will make that change.
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