MobiFlight Community Support

Hey I got a problem here

I don't use the 7 segment module like written in the tutorials. So I build my self a single digit 7 segments LED, three of them and then glue it so I got 3 digits. I already connect them to the max7219 chip correctly without resistors. Do I need resistors for this? Because everytime I tried to run the mobiflight, the LEDs not dimming itself so there's no numbers showing. Even when I tested it in the config. I don't know if I am using a wrong resistors or not, but all I see is a few segments are dimming but the other segment is still on, so I can't see the numbers. I use a 5161BS LEDs which have 30 mA forward current so as I calculate for the resistance it would be around 160 ohm. Am I right? Please help me. I've been working on this for months but no luck

HI

I will recommend to use pre Build Max7219 Tubes with removeabale Displays.....
http://www.banggood.com/MAX7219-Red-8-Bit-Digital-Tube-LED-Display-Module-For-Arduino-MCU-p-907849.html?rmmds=search

I think with a raw max7219 Chip you need to connect the resistor by youreself..... in this prebuild ttubes the resistor is already include.
If you like to use youre own Display just wire it instead of the 2x 4 Displays( simply remove this diggits and use youre own)

Ok... this costs 4 $ for a tube... But this tubes normaly work fine... Youre own building maby got solder issues at all.

HI

I will recommend to use pre Build Max7219 Tubes with removeabale Displays.....
http://www.banggood.com/MAX7219-Red-8-Bit-Digital-Tube-LED-Display-Module-For-Arduino-MCU-p-907849.html?rmmds=search

I think with a raw max7219 Chip you need to connect the resistor by youreself..... in this prebuild ttubes the resistor is already include.
If you like to use youre own Display just wire it instead of the 2x 4 Displays( simply remove this diggits and use youre own)

Ok... this costs 4 $ for a tube... But this tubes normaly work fine... Youre own building maby got solder issues at all.

i already buy one now, but its a matrix dot module so i think its the same. but i still can't make it work. is it because my LEDs are common anode? please help me

Hi everyone

Does mobiflight supports common anode 7 segments LED?

No. The max7/19 chip drives common cathode displays.

No. The max7/19 chip drives common cathode displays.

Thanks for the answer, now I know what made it not working

Borrowing this old thread instead of posting a new one. I have ordered the green Max7219 boards from Ebay. I am planning on using them on the 737 OH which means I need to find 7 segment displays with green and yellow color, but I am struggling to find any.
Has anyone of you had any luck finding them?

Also, will it fit straight on without modifications?

All the best

Oskar

Hi Oskar,

try here:

https://www.ebay.com/itm/0-56-LED-7-Segment-4-Digit-Common-cathode-MAX7219-arduino-Blue-White-Green/121031922000?hash=item1c2e109150:g:96gAAOxyzGlQ6qwo

https://www.ebay.com/itm/10pcs-0-56-inch-4-digit-led-display-7-seg-segment-Common-cathode-green/131856499962?hash=item1eb34284fa:g:LLkAAOSwJb9WqxZJ

https://www.ebay.com/itm/HT16K33-8-Digit-7-Segment-0-54-inch-Numeric-LED-I2C-interface-Arduino-Raspberry/283157095251?var=583564233721&hash=item41ed7a6353:m:mRrdAGVm90JCi2P0hhh0sJw

Thank you Stephan.

I think that 0,56" is too big or am I wrong?
I think the boards are delivered with 0.36".
I don't know about the ELEC panel, but for FLT ALT and LAND ALT 0.36" seems to fit fine.

Oskar,

0,56" are 14mm. That is the normal height of the MAX7219-Display-Boards. Please look for MAX7219 on ebay.com

If you want your displays smaller then can you do that, of course.
Note only common cathode and possibly the indication that the Displays are MAX7219 compatible.

Just measured the ones I have and you are totally right as always! Will make an order, thank you for helping out.

Still a bit confused. From what I can see the 4 digit displays have a total of 12 pins. But when looking at 2 digit displays on Ebay it has a total of 10 pins. In My world half the digits should mean half the pins

Also found a 1 digit display with 10 pins, I suppose they won't work then? Confusing to say the least.

Hi Oskar,

if you have a single 7-Segment-Display you have, like the name says 7 Segments A, B, C, D, E, F and G. The first 7 pins. The 8th one ist the decimal Point DP. The you have 2 Pins for the common cathode (or anode). Finally you have 10 Pins for this display. If you take a 2nd single Display you have 20 Pins and so on.

If you have 4 digits of 7 segment Display you have only 12 Pins. That's normal. All 8 pins of the individual segments are connected in parallel, as well as the decimal point.
So again you have 8 pins for the segments with decimal point and 4 common cathodes. One cathode per digit. Together in summary 12 connections.

This type of connection makes it easier with regard to the wiring and also with regard to a drive with a multiplexer. Our eye is perceptibly sluggish and e.g. with MAX7219, the digits are driven at 1kHz, which is 1000 times per second. This creates a permanent display to the eye, although the display actually changes so frequently.
So that a user (of course also the industry) does not have to work so much wiring, the connections are reduced to the necessary degree.
That is the whole secret.
If you want to do the work, you can get individual digits in any color and cabling them conventionally. Decisive is that you come at the end of the number of connections to the driver, as if you had a self-contained display. Simply connect all A-segments together, all B-segments etc. So you will get 8 single wires for the segments and the number of cathodes (or anodes) off every Digit. These wires are then to be connected to the driver chip (i.e. MAX 7219).

I hope to have eliminated your confusion

For better understanding.....

A Display (Whatver 1,2,3,4,5,6,7,8 Diggits) ALWAYS need 8 Segment Lines .... (Seg A-G and DP )
Adittional it must have 1 Common cathode line per Diggit.... So a 3 Diggit Display needs 3 Cathodes.
Summary.... All Displays MUST have minnimum 8 Lines + X Lines ( X is number of diggits)

About confusion.
the 1 Diggit Display basicly need 9 Lines.... But in case of cheap production most displays have 10 Lines ( 5 Left 5 Right ) . this is better to build by industrial machines.
In THAT case the 10th Line is simply combinded with the Common Cathode.... so Both Pins are the same.

Additional Information:
Some Displays have MORE Segments as 8.... For example some 4 Diggit Displays have a ":" Doublepoint in the middle to use them for a digital Clock! lie 11:22
those Displays have a 9th Segment line that is light this double Point .... Here we simply not wire it to the max cause we not need it !

Other Displays have another Segments... for example a "°" degrees symbol for thermometers..... Here the same.... simply not wire it.

Finaly some Displays have Single segment lines for each Diggit ..... For example some 2 Diggit Displays have 18 Pins .... here Both Displays have there own Segment lines (2x8) and there own Common Cathodes .... So 8+8+2 = 18

Summary:
You need always all Segment lines from all Diggits combined.... ALL Seg A must be combined to ONE Seg A Wire to the Max .... Same for SegB - G and DP .
Finaly you need 1 Cathode for every Diggit as single wire to the Max.
You can finaly build EVERY Display ( Color Size etc) with this system if you understand the basics !

Thanks a lot both of you, I think I am slowly beginning to understand. One Max7219 tube module supports 8 digits (2*4). If I would like to connect 8 individual 1 digit displays would it be right to (for example) find the pin for the a-segment on each 1 digit display and serial connect 4 of them to the first a-segment output pin on the board? And so on for every segment. And then use the next 4 displays for the remaning output pins.

Am I getting this right?