Sorry to hear that. Not having bypass caps can cause many strange problems. If they are missing, it is the first thing that should be attempted to correct the problem. Even though the problem must be elsewhere in your circuit, you should still add the 0.1uF cap to reach board. As I said, they are not optional.
The forward voltage is not shown on the vendor's page. This is a sign that you should choose another vendor, because that vendor does not understand the importance of such data.
White LEDs normally have a forward voltage of about 3.2V. max7219 should be fine to drive them. With the max chip, you will of course need a 0.1uF cap, and a 10uF cap also.
Thanks. So good news on the max7219 front. I will know soon enough if I amde any more mistakes in this project.
In a meantime I am stuck with this problem. If it was a soldering problem I would have these possible errors:
segment not connected - result: Segment not properly lit
VCC GND not properly connected. Result: the whole module would be off
control pins ST_CP SH_CP Data incorrestly connected. Result: you would not be able to properly input 0 and 1s into the shift register or output them to the output pins
None of these correspond to what I have. The process of loading the register and outputing data works but only if I touch ST_CP pin.
Just an idea . Are there different types of shift registers where in ones OE anables output when low and in others when High.
That would be a reasonable explanation. When I touch the st_pc I also potentially touch OE activiating the output. In my setup OE is idle .
Or because it is not connected to GND it floats.
Where is the schematic for your board?
You need to control MR and OE/.
MR is usually pulled high and left there.
OE/ is usually pulled low and left there, or you can drive it with a PWM pin for dimming.
It could be as simple as one of these, with perhaps the DataOut pin connected to to the header.
@CrossRoads is right, the rest of us should have spotted that much sooner.
idle == floating
This is why it's better to post a proper schematic than a Fritzing/Tinkercad wiring diagram. In your diagram I saw 2 unconnected pins, but as I haven't memorized the pin positions on 74hc595 or any other chip, I ignored them. If I you had posted a schematic, I would have seen that the unconnected pins were labelled OE and MR and known immediately that there was a problem!
