Hello togehter,

I´m having a very weird behaviour of the LEDs and the 7seg displays. The strange thing for me, is that it was working fine and after I updated SimVim to the latest version things started to get weird. LEDs are coming on and off randomly, 7segs (Max drivers) are not working anymore, some LEDs dont go on at all...

Actually, I dont think that the root cause lies in the Software because I had this behaviour some months ago before it had started to function, but rather in a faulty wiring from my side generating ground loops and interference everywere.

I will start a troubleshooting sequence to try to look down the error. Of some of the other posts in the forum I got to gather some ideas (and questions):

1) Grounding:

- everything grounded to 1 main GND Bus ("star"-connection) avoiding circular loops between the connection elements -> I have mainly solved this. Max7219s are going directly to the -V of the power source, aswell as the Output multiplexer for the 7-segs. The Led drivers (DM13A) have Pin #1 and #21 connected together and then conected directly to the -V of the power source.   

- the GND Bus is to be a thick copper wire -> as I dont have this wire this will be last thing to try. As of today everything is going through solid core wires (like Bell wires.. not shure about the AWG number but aprox. 0,5mm in core diameter) to the -V of the power source. I have a breadboard strip gathering all GNDs to the power source -V.

- The power source itself has GND connection to the my house main GND (Green/Yellow cable). -> is this a problem?

- Could you give me further practical tips to look down errors regarding grounding? Is there a way to measure ground loops with multimeter?

2) DM13A drivers: Add a pull-down resistor between Pin #3 and GND of about R=1 - 3 kOhm. This should be pretty easy to do as I have made some pinboards for the drivers.

3) Wiring: i have a pretty clean wiring (in my opinion.. well you can see all of the main components so not too messy), BUT layed out in different levels/heights... could this be an interference issue?

4) For the 7segs I´m pretty confused because they used to work and all of a sudden they dont anymore and I´m out of clues.

5) Some other ideas? Different approach order?

I would be very gratefull if you could give me some hints if this is the right way to go or am I getting over something?

 Here a picture of the build

Thank you a lot!


1 week ago in LEDs, Digital Output by

2 Answers

First this - "... Max7219s are going directly to the -V of the power source..". Why -V, maybe +V
-V should be connected to main GND as all other supplies.

1 week ago by
Hi Vlad,

Yes I meant, that the Max7219s grounds are connected to the -V of the power source. -> Maybe there is my Problem?

What exactly is beeing normaly connected to the -V of the power source?

Thanks, Diego.
Update: So I´m done with #2 (pull-down resistor). This did not fix the problem, but when i´m pluging in the power source LEDs are not going on like wild now. They stay off until xplane connects with simvim.

I think, next will be GND Bus wiring with thick copper wire...

Im still a little confuse, cause things were working perfect 2 weeks ago. @Vlad: was there any change in the software, that could have impact in how the hardware gets connected?

Thanks for some advice on what should I do next...


5 days ago by