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Merikarhu
Posts: 13
Hey again !

Think about b737 mcp, you need atleast 17 leds to illuminate all switches and signs (like MA). You can do it by using 1 input from arduino card. But i was thinking that if i use Max7221/7219 IC i could use 8-64 leds for one module. Have anybody tried it ? or do you have better idea. Feels like a waste I/O ports to use them for single led when IC can do it for 2-3 ports


Let me know your ideas !
2017-01-27 23:06
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pizman82
From: ETSI, Germany
Posts: 3732
Supporter
Hi.

Other user request this some months ago....

I Think with a own programmed software its no problem. But at the moment Mobiflight not support Single Segment Coding.... So you define for 7 Segment Displays a Number from 0-9 or some Signs like "a,b,c" .
I´m not shure if Mobiflight calculate a Number for exmaple "1" and send the needed Segments by a 8 Bit Block OR if Max7219 use a own logic and mobiflight only send "1" and the Max calculate what segments are light up.
In Both Ways it should be posible to do what you want but Sebastian need to change some code in Mobiflight and allow us to define the Full 128 possible Combinations of an Diggit. and not only 0-9, a,b,c,and so on.

BUT:
The question is.... Is this profitable....
You need to build a own Matrix or Hack a Led Matrix Board.... Lots of soldering and wire work. And if a Issue in System you have to search long time to find.
Two Adrionos cost less then 20$ att all Do you realy want to work lots of hours longer to save this ?
Good Luck !
2017-01-28 01:36
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Merikarhu
Posts: 13
Hello,

actually two megas would be easiest way to go. Thank you and lets hope developers read this and find some solutions for batches of leds :)=
2017-01-28 10:58
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corco19@hotmail.com
Posts: 25
Remember that Mega Boards, can supply 200ma power to led at the same time . Each LED consumption is around 20ma, then you can supply about 10 leds for each board.

So, if they all are going to stay ON at the same time, you all need to connect half leds on a board, and the other half, on the other.
2017-01-28 11:43
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avidflyer
Posts: 138
or you use low current LED´s with 2mA per LED
2017-01-28 15:02
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Merikarhu
Posts: 13
iconcorco19@hotmail.com:

Remember that Mega Boards, can supply 200ma power to led at the same time . Each LED consumption is around 20ma, then you can supply about 10 leds for each board.

So, if they all are going to stay ON at the same time, you all need to connect half leds on a board, and the other half, on the other.



Where you find information about 200ma maximum CURRENT drainage, usb port is capable of 500ma current flow and i do have 9v DC jack for 500-1000ma usage.
I just rechecked documentation and it's clearly stating that each digital input is supplying 20-40ma. Automatic pullup resistor will fail if current exceeds that.
2017-01-28 15:53
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pizman82
From: ETSI, Germany
Posts: 3732
Supporter
To Low Current LED´s
If you want to use Max Modules then you have to work with Low Current too.... ( The LED´s in 7 Segmenter are real low )


About the 200mA Problem.

This information came from Another User in a different Topic on this Board..... But i do a research and found This....
http://playground.arduino.cc/Main/ArduinoPinCurrentLimitations

Read the Part about Mega Boards... Looks like the 200mA Information is not 100% correct.... It´s true for ONE Ground Pin.... But the Mega got 4 GRD´s
So we can already work with 40 LED if we split always 10 pieces to one of the GRD´s.

AND Again as i told in other Thread..... Remeber that ALL LED´s normaly not ON same time ( Or if all on its just for some Seconds) AND The Limit is not a absolute Border. Arduino only says "This can demage the Board" I´m belive a Power of 300mA (or more) for just some Seconds maby 1-2 times per hour will not kill youre board immediately.
Not good and maby reducing lifetime ob Board.... But think about how many things in daylie life we use "over" recommend limits. Every self Overclocked Processor get damaged all the time if we belive in the manual of manifactur.
Good Luck !
2017-01-28 16:29
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tommy1332
Posts: 26
iconQuote:

Read the Part about Mega Boards... Looks like the 200mA Information is not 100% correct.... It´s true for ONE Ground Pin.... But the Mega got 4 GRD´s


That's correct. But the Arduino connects all GND pins of the ATmega. The problem is you can't control the current to each pin regardless which pin of the header you use.
The current will not necessarily be divided evenly between the pins. If you want to make sure nothing breaks you can't use more than 200mA.

Also please remember:
iconhttp://playground.arduino.cc/Main/ArduinoPinCurrentLimitations:

Also, please note that this is absolute maximum rating and exposing the device to absolute maximum conditions for longer duration of time could possibly cause damage to the device.


You should always stay a lot lower than these ratings.
2017-01-28 16:48
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Merikarhu
Posts: 13
One way is to have external power supply and control leds by using transistor. That means Arduino acts like a boss, giving orders and workers light up leds :)
2017-01-28 22:10
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pizman82
From: ETSI, Germany
Posts: 3732
Supporter
@ Tommy.

Again i don´t want to say youre wrong ! But this sounds verry passiv. "for longer duration" "recommend" "Could happen" "Maby will"
I understand that Arduino have to write this cause lot´s of people with a burned Board will request garantee if this is not written....
If a user want no risk he can do what Arduino or you explane..... The question is..... How much is the risk ?

I just can say here i will build my Elements with no thinking about these Limits.... If i need 40 LED 20mA on a board then i will connect them.
If the Board get killed i just use another one for 10$. If i kill 2-3 Boards in short time THEN i start thinking about and then i will report here.
But i´m pretty sure that a my Arduiono will work without issues for the next Years altough i conneckt 40 LED with 800mA on the Grd
Lets find out ;)
Good Luck !
2017-01-28 23:17
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tommy1332
Posts: 26
First of all you are free to do what you want. Let me know if it's working fine.

My opinion to this:
It might work because not every LED is on at the same time.
If you want to "professionally" build your HC you should consider this. It's as you say, the arduinos are cheap so wouldn't it be better to decrease the chance of failure?

By the way: LEDs do light up decently at a lot less current. Low current LEDs only require like 3mA to light up bright enough. It's worth a try.
2017-01-28 23:42
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pizman82
From: ETSI, Germany
Posts: 3732
Supporter
icontommy1332:


If you want to "professionally" build your HC you should consider this. It's as you say, the arduinos are cheap so wouldn't it be better to decrease the chance of failure?
By the way: LEDs do light up decently at a lot less current. Low current LEDs only require like 3mA to light up bright enough. It's worth a try.



I Agree. We always should split needed devices to all Arduinos we use in this Element..... (If posible)
And i Agree too... If Brightness is enough ( for a control light) then low current is a good solution.

But i already not understand completly Why you define the Limit of 200mA per Board when Arduino itself say it´s 800 after all.

Please explane me youre following argument again.....

icontommy1332:


But the Arduino connects all GND pins of the ATmega. The problem is you can't control the current to each pin regardless which pin of the header you use.
The current will not necessarily be divided evenly between the pins. If you want to make sure nothing breaks you can't use more than 200mA.



Why i can´t Controll this ??

For Example.... I will connect 32 LED (20mA) . So i always use 1 GRD Pin for 8 LED. 8 * 20mA = 160mA ( 40 below the 200 limit for single GRD Pin)
On the shared GRD of the Board 4*160= 640mA can come in ( 160 below the 800 Limit for Board GRD )
Why should the current not be devided between the pins here.... Only the current from the connected LEd can go through this pin right ?


Please explane me in what way or situation it can be a problem. In my point of view our rates are lot enough below BOTH Limits.
Right ?

And again sorry for additional question. i don´t want to discredit you. I just try to learn. If you want anwser in german in other thread for better understanding.
Good Luck !
2017-01-29 02:42
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tommy1332
Posts: 26
After thinking some time and reading the datasheet I think your 640mA draw might be within specifications. I think I was wrong.
Unfortunately the datasheet does not say anything about the current distribution between the 4 VCC and GND pins but assuming the distribution is almost equal you shouldn't run into any problems.
2017-01-29 14:57
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Merikarhu
Posts: 13
Documentation clearly says that EACH vcc and GND has max limit of 200ma. It's just kinda shady what they mean by it :D
2017-01-29 16:00
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tommy1332
Posts: 26
Noone questioned that this is valid for each pin. It's just not written clearly how the current will divide onto these pins.
2017-01-29 16:31
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