Good morning and Happy New Year 2024 to everyone. A few days ago I posted in the Mobiflight General Forum some questions about some problems I'm having with the Max7219 7-segment displays -(MAX7219 Same problems - same solution?). I have read that queries are being moved to Discord, giving this platform greater prominence. Allow me to copy here the last question I made in the Forum in case someone can help me: "I still have problems with the displays. I have bought a 5v 20A power supply, I have connected it as indicated in the forum (GND connected to the arduino and VCC to the power supply, I use pins CLK 23, CS 25 and CLK 27), I have changed cables, etc. etc When doing the test I can't get 12345678 to appear. The log shows: "MobiflightLedModule. Display():Command:SetModule<1.0.0.10000000.0.255>" Does anyone know what this means? Give any clue to know the mistake I'm making? " Thank you very much
#Log Message installing Led display Max7219
halcyon halo
marble turret
Hi, just to make sure the cableing. Power supply +5V goes to VCC of MAX tube and power supply GND goes to both MAX GND and Arduino GND ?
iron rose
The log message, if you have "Debug" level selected for log, just means it is sending a value to the module.
Make sure your DIN, CS and CLK are set to the correct pins, some MAX7219 modules have the pins in DIN CLK CS order and its not that hard to accidentally have them swapped..
halcyon halo
Thank you Roberto and Tomas. The power supply is connected as indicated. And the pins are assigned by me personally in Mobiflight (I do not maintain the pins that Mobiflight offers)....someone is talking about connecting a resistor or capacitor in the LED module, do you know anything about this? Would it be necessary? Thank you
oak yew
Can you show a picture of your wiring from the led module to arduino and power connection?
One led module can be powered from the arduino 5v pin directly without the need of an external power supply. I would try to simplify by disconnecting the external supply for now.
Max7219 modules are known to be sensitive to electrical noise. If this is the case, capacitors can be installed as close to the chip as possible.
halcyon halo
Good morning Jaime. Thanks for your interest. If I connect the LED module directly to the Arduino and do the test, it doesn't work. When doing the test it comes out as a small flash and everything turns off. If I connect it to the power supply and do the test (12345678) now only 10000000 appears. The connections are provisional - until I know if the LED module works I will not install it permanently (photo attached). I have made sure that they are as stable as possible. I don't have much idea about electronics, could you please tell me exactly where to install the capacitors in the module? Thank you so much
oak yew
Picture of the wiring?
Did you connect the external power supply GND to the arduino GND? It is important that GND on both be connected together
Most led modules have an empty place marked C2 where a 10uf polarized capacitor can be soldered.
iron rose
this is an example from my testing
oak yew
Yeah, nice picture. The C2 label might be on the opposite side hidden under the digits.
halcyon halo
Thanks Jaime and Tuomas. Yes, the GND of the external power supply is connected to the Arduino. I'll look for a 10 uf polarized capacitor and test it to see if it works. I will inform you about the result. Thank you very much.
iron rose
I have one of these 8 digit modules that worked fine
then this other one would just flash 8.8.8.8.8.8.8.8. for me or just flicker on and off
until I put this capacitor in
halcyon halo
Hello again. It does not work. I have soldered the 10uf capacitor as indicated. I have purchased a new MEGA2560 board. I have connected it to the power supply and the GND to the board and nothing. Attached photos. Now what I get is that 10000 0 appears on the display. I have checked the solders and cables and apparently everything is fine. What other tests can I do? any ideas?. I have bought 5 new green displays on Ebay, in case the ones I bought had been damaged or defective.........
oak yew
Except for the ugly soldering job, I see nothing obviously wrong (I hope you didn't accidentally create any solder bridges).
I would not connect the external power supply GND on one side of the arduino and the led display GND to the other side. I think that forces all the return current to flow through the arduino. Try going from the led display directly to the power supply with a side GND connection to the arduino.
Also, if only doing one led module, the external power supply is not really required.
halcyon halo
Ha ha ha. Thanks Jaime. Welding is not my strong suit, although I have repeated it many times until I got it right. I think it is a tin problem (HUAREW 0.8 mm, Sn99-Ag0.3-Cu0.7 Flux 2.0%). My idea is to use 5 LED display modules, that's why I use the power supply. All the best
iron rose
yeah we all begin soldering sometime, its usually worth a bit of time to watch some youtube tutorials on soldering, its a lot about technique
halcyon halo
Tuomas already did it, and I try to do it as best as possible, but as I mentioned, I think it is a problem with the solder, flux or heat with the soldering iron. By the way, how can I know if the LED module is damaged? Thank you
iron rose
yeah, I think small enough soldering iron is important too, but yeah, and this is not at all meant as an insult or anything
its just good to get soldering stuff right to avoid connection problems
cold solder joints can also cause trouble
oak yew
Tuomas already did it, and I try to do it as best as possible, but as I mentione...
for me, flux is what makes all the difference between ugly clumpy solders and clean shiny solders.
it makes the molten metal just flow more easily and fill the voids
hallow bluff
i dont use flux at all... my solder wire has a flux/rosin core and that is all i need.
I have seen people use flux excessively, which can lead to problems like a short circuit too. It is important to clean up afterwards and remove all excess flux from around the solder joints
oak yew
I also use a flux/rosin core solder wire, but often times it is not enough.
and you can see the difference instantly on how the molten solder behaves
hallow bluff
in my opinion a good solder joint is the right temp on the iron, rather higher than lower, and the right amount of time to allow for heat transfer, and then just be cautios with the amount of solder that you apply... and try to get it close to the pad
i think I have easily like 80,000 solder joints per year 😄
oak yew
agree the excess flux should be cleaned with IPA afterwards.