MobiFlight Community Support

Hello
I have a problem with my module.max 7219 led 7 segments they are power 5v on external power 5v 3A
But wen the power supply is off and the arduino board its connect to usb power the max 7219 comes very very hot and after he is dead
An idea?
Thanks

Hi

Sorry but i don´t understand complete what you do here....
You use 5v External Power on the Max and USB Power for the Arduino...... What GRD do you use for the Max ???

I´m not a professional in electrics.... But i think it´s not needed or recommend to power the Max tubes external.... If you think youre hole outputs need more power then the 500ma from youre USB ( Or you don´t want this from the USB in other reasons ) then simply connect youre External Power to the Arduino !

So i would recommend to set 5v and GRD of the MaxTubes always on the SAME Arduino that you use for the Data Lines !

Maby a advanced User can give you more informations here !

Hi Banzai,

Pizman is very right with his scheme of things! For one MAX-chip you do not need an extra power supply. A lot of users operates with 10 or more MAX boards an they do not need any extra power addionally.

First you should try a correct connection of a tube like the MF tutorial with no extra power (Maybe that you need one with 30 or more tubes )
If your MAX chip becomes very hot is a sign of wrong connection, i.e. a short circuit or wrong soldering or missing GND connection from the external power supply. So check the MAX board in view of soldering bridges and cabling.

Next error source maybe the power connection itself. Plug off the external power and try only with the USB power - like pizman advised.
If you provide the MAX board with external power (not necessary) check the connections in view of correct connection.

Please notice: if you provide your MAX board with 5V your MAX works only with ~4.3V. Reason is the Diode (labeled as D1 on the board). If you construct a daisy chain with the Max boards look for a seperate connection with 5V to every MAX board.

It would be nice to tell us about your experiences and what you have figured out.

hello thanks you for reply
then i want to make one mcp for the pmdg 737
so i follow this tuto link : https://drive.google.com/file/d/0B37KGrhnttSrMzhkNHJWbzFpMUE/view?usp=sharing

i use one power supply with four module max 7219 daisy chain the 5V an te GND of the power supply is connect to the first Max-chip,

DIN,CS,CLK connect to arduino mega board and the next tree max chip are chaining to the first module

when i connect just arduino usb nothing working on Max-chip chaining but with juste one connect to arduino its ok

Hi Banzai,

the Tutorial is ok. But therein seems to be basically an error. If you did not provide every MAX board with +5V the fourth one and the following ones should not work anymore. Reason is D1 on the MAX board. D1 reduces the voltage on every following board by ~0,7V . 2nd has 4.3v, 3rd 3.7V and 4th board 3V. So all boards after the 3rd should not work anymore and make .undefined signs or becomes dark. If you have a measurement instrument please check it out
This effects to all MAX boards in the Daisy Chain. Remedial measure: you can bridge D1 with a wire, unsoldering D1 and remove them therefore a wire strap or you provide every board with 5V separetly.
DIN/DOUT,CS, CLK and GND should be Daisy chained from module to module - not so 5V. 5V to every board separatly.
Do me the favour an throw the external power supply in the wind. - you did not need it - sure! Every standard USB-Port is loadable (maximum) with 500mA.
If you want to use it absolutely, note to connect it with GND to the boards AND to the Arduino. Otherwise you will have two different GND potentials - and that is electrical nonsense and can not work. GND is at simple wirings the unique common potential of every single component with an own power supply.
Look that you power-up the arduino and the MAX modules at the same time and then start MobiFlight. Only in this way is guaranteed that the modules got an init from MF and they will work well.
If only one module works with your arduino please check as follows: connect the first module to the arduino and check it with the test-option of Mobiflight: mappings and the entry for the module (...) -> display and then the blu test-triangle. If all stated digits shows a different number the module is ok. Built the chain and take the second on and test it in the same way.
Note: you should define an own config for this test so you need not to change your original config.
Also note: save your test-config always to the arduino having changed something.
Last note: check your original config having errors
If all works fine you can built your module chain and test it completely.
Did you have now a better result than before? Please tell us - every problem has a solution

ok i test
just one precision about that:
"If you want to use it absolutely, note to connect it with GND to the boards AND to the Arduino"

where i connect GND on Arduino

Ahh, you want use your external power supply further on. You should have two cables. a blue (or black) one and a red one (?). Red should be +5V and the black is GND, GRD or 0V - all the same.
The 5V to your moduls (one separatly to each modul), GND to the modules and GND to the arduino.I assume that you use an arduino MEGA. The arduino boards has several GND terminals on its adapter terminals. They were all named with the letters GND. You can use one of them.
Bonne chance

hi
Ok i do not know if i will use the power supply just in case or!
I tested the modules and two did not work properly
I have to order again!
Thank you for your help

Hi Banzai,

did you test every module separatly on in the chain?
Please check every module separatly. Then with 2, the with 3 and so on.
You should not order new ones before you have checked the others.

Hey Guys...

maby for better understanding there is a "recommend" Testing Situation !

Note... Youre Display got 2 posible issue spots.... 1. The Input Pins, 2. The Output Pins.

So there is a 100% Testing Situation to check this....

1. Test ( Input Side)
Create a Device for a Max7219 Tube ( Use "NUM1" for this .... NO Chain.... Only 1 Tube !!!
Create a Output Config for this Device
Wire ONE Tube to this Pins on Arduino ( The 3 Data Lines AND 5v and GRD.... NOT use a external Power here !! )
Now Use the "Test" Button in the Config/Display Tab.....
If Display Itself is OK.... AND the 5 Input Pins (Left side) are OK then there will be shown 12345678 on the Display !

NOW do this Test with EVERY Single Displaytube you like to use later in a casscade.
After THIS You can Confirm that ALL Displays work itself and ALL get a working Input Pin block !

***
2. Test ( Output Side)
Create a Device for a TWO Max Row "NUM2"
Create a Config and use the SECOND Tube of this device
Now wire the tube you like to test on First Position ( Direct after Arduino) and set a second one behind
Again not use External Power... Data Lines and 5v/GRD go from Arduino to Tube 1 and then From Tube1 Output to Tube 2 Input !!!
Now use again the Test Button in Config/Display Tab .
If everything is ok then the SECOND Tube should show 12345678
IF NOT then the Output Pins of Tube 1 are broke !!! ( remeber you test in Step1 before that tube 2 itself is working if you use it in a single setup !)

Now test all youre Displays.... Use the Disply you like to test always as First Tube in the Row !

**************************

Finaly.... You not need to send this Displays back.... Chineese Displays normaly 20-30% are broke when you buy them.... You only have to resolder the Pinheaders (mostly on the Output side)
AND again like Stephan say.... i high recommen to NOT use External Power on Displays !.... If you realy want it then Power your Arduino external BUT then power the Tubes over the Arduino internal 5v and GRD !

Hello
I tested all the modules one by one according to the method two modules dysfunction, one shows nothing at all and the other remains always on, with the last digit brighter than the others.then i check the diodes its ok
I also resolder to see same results I think that they are dead

Hello,
Are you using Arduino Mega 2560? The Arduino Mega has +5V DC output pins. You must use one of those +5V DC output pins. Do not use external power supply as pizman82 said in the first reply.

Hi guys, I came across this post and I saw that I was the offending author of said tutorial. This unfortunately is version 1 and the current website is at version 4.

I have learned a lot over the last year, and this version was quickly amended as it had some major flaws as mentioned above.

1) each max7219 must be powered directly and not daisy chained as the voltage does indeed drop through each unit.

2) if using a external power supply, the ground of the external unit must be connected to the ground of the arduino.

3) I have found from experience and the arduino website, that external power is a must past 3 more daisy chained max7219 boards. Each board is capable of pulling 170 mA each. However, this has never damaged anything, and the boards just start to display random digits.

I found that the boards just stopped working completely, especially of an encoder was then adjusted.

As for the overheating issue, this has occurred several times to me, and it really was down to bad batches from ebay and indeed wiringbthem up wrong. If your quick you can save the board, however, i have written my fair share off.

Another tip I have found is to keep the wires from the arduino to the max board as short as possible.

I hope this helps to set things straight, as a lot of people have now contributed to getting the document up to date. There is now a lot more information in the new doc.

Kind regards

Karl

hello
Thank you karl for these details,
I received two new max7219 card and it works
You say there is a new tutorial, you have a link to give me
thank you

Hi banzai,

Sorry for that he delay, been away with work. My email address is karl.clarke@hotmail.com.
Email me and I'll send you the new version. It also explains how to connect a whole mcp up using only 3 max7219 boards. Much easier and way more reliable.

kind regards,

Karl