So as some of you have noticed, i have asked about MAX7219 problem on the other topic that was about I2C so decided to make this as a new topic as i am having problems with MAX displays.
To explain what the problem is:
- If i have one display connected, it works great, but as soon as i add a second one, both displays start flickering, showing random numbers, or they just work for 10 seconds and then go crazy.
- MAX chip is getting really hot. If i have just one module there is no heat issue.
Now for the setup:
- I am using small (10mm) 7 segment displays as on the image below
I have removed diode D1 as many other people suggested
I have tried connecting SPI wires on various pins on the board, all with the same result. Using MEGA board i have them at pins 50, 52 and 53 as someone suggested that those are hardware SPI pins for MEGA. Same problem as with any other pin combination
i am also aware that i should add capacitor to those two small holes bellow D1 diode but now the question is, is it ok to use ceramic cap or it has to be electrolytic? I am aware those are not the same. For electrolytic, i am not sure about polarity... looking at the picture, negative side should go left?
I have the 5V and GND connected on both sides of the daisy chain, if i just leave the power and GND from the first module, same thing happens but the displays are dimmer.
displays are set to full brightness in the code.
i am using external power supply that powers MEGA and the displays. GND for both MEGA and displays are connected.
in the code, i have set up the pin numbers and 2 as a number of devices, when they both work for a few moments they show correct characters on correct positions.
At one point i made them both to work for a few hours, they did heat up but not that much, then after a few hours 2nd in chain module started showing odd characters on the display along with correct ones.
Now, i am aware that these are cheap Chinese displays but they all work fine on their own, no problems whatsoever, no heating either, but as soon as i add one more, everything goes south.
Main concern here is the heating problem as i think this will point to the thing i am doing wrong.
Any help would be highly appreciated.
Many thanks, Alek