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By FartingMonkey92
#66452
Firstly, keep learning! It is a fun hobby, honestly. :wink:

You see the 'shaded box' attached to the top, right side pin of your Arduino with one line? Inline with the LED modules. That can go.

Second, the pupose of the sink drivers is that each row of LEDs on the modules is never on at the same time. The Arduino pulses each channel in sequence at a fast rate to look like their on all the time, as you send data to the shift registers.

Third, as only 1 row of the modules are on at one time, the total usage of current is a maximum of 800ma.

10ma * 8 * 10 = 800ma

Fourth, each channel of the sink drivers can sink 500ma. You can parallel the channels for higher current handling.
By daok
#66465
FartingMonkey92 wrote:Firstly, keep learning! It is a fun hobby, honestly. :wink:

You see the 'shaded box' attached to the top, right side pin of your Arduino with one line? Inline with the LED modules. That can go.

Second, the pupose of the sink drivers is that each row of LEDs on the modules is never on at the same time. The Arduino pulses each channel in sequence at a fast rate to look like their on all the time, as you send data to the shift registers.

Third, as only 1 row of the modules are on at one time, the total usage of current is a maximum of 800ma.

10ma * 8 * 10 = 800ma

Fourth, each channel of the sink drivers can sink 500ma. You can parallel the channels for higher current handling.
You are very bright! and I like how you explain me stuff. Thank!

I have ordered the Matrix Led from Ebay, and a big breadboard to be able to try it before solding anything. I will try to find from a local store or maybe on Internet: 2 Sink Driver and some 11 Shift Register. I will tommorow calculate the resistant required and will draw the way I could use 2 Sink Driver in parallel and post it here. This way you will be able to validate me and telling me if I do error. See you tommorow! :)
Last edited by daok on Tue Feb 17, 2009 3:37 pm, edited 1 time in total.
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By FartingMonkey92
#66467
Thanks! :wink:
As for the shift registers and sink drivers, you should get quite a few more than needed, bits can go PoP... :D
And you should use more than 2 sink drivers as you may exceed the 1watt limit per channel.
And if you make 10 displays, you'll need at least 10 shift registers! Maybe as a start, 1 for every 2 displays?

If you start with one display, it'll be easier for you to follow and debug.
May i suggest you build steps 1-2 from the Arduino - ShiftOut tutorial and we go from there?
Or go from the Tinkerblog page but with just one shift register?

Oh and Sparkfun sell SR's and SD's... :wink:
By daok
#66492
Here is my homework for tonight. I simplify everything to only 2 DotMatrix. This way the graphic will be less heavy to read. I added the resistance and added the parallel for the Sink Driver.

Image

You are absolutly right, I think I should start with the tutorial you show me and start with 1 DotMatrix than 2... to finally have all of them.

I will buy from SparkFun the missing part : register shifter and the sink driver. For the Register Shifter I will take I think the Shift Register 8-Bit - 74HC595 (not the high voltage the normal one), and for the SinkDriver the ULN2803.

When you have time, tell me if I did an error :D
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By FartingMonkey92
#66518
We're getting there... :wink:
However, that 'shaded chip' is still there! Number 3 can be erased, good idea numbering them in ya diagram.

But, the value for the resitors is wrong! I got 300ohm from: R = (5 - 2) / 0.01
So then next standard resistor is around 330ohm. Always go up in value...
And you need to move your resitors to between the shift registers and the displays. Very important! :wink:

You will have to power your modules from a serperate 5V supply, tho.
As with just one display, ~80ma is too much for the 5V pin on the Arduino...

One other thing we need to do is to work out the pinout of the displays... Should be fun.
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By FartingMonkey92
#66520
Also, a little supplement...

The lines from the Arduino don't actually supply the current for the chips/LEDs, just the logic level (high or low) to operate the shift registers and sink drivers which supply the current... :wink:

I really need to get myself a white board... Good work! :wink:

When you've got the parts, we will talk about which pins to use.

EEK!
You might not be able to drive the LEDs at 10ma, we might have to work out the calculation again and hope they are bright enough to see...

If you haven't bought any chips, we can find a different place...
Sparkfun don't sell the one they use in their products... :roll:

Ideally you want a SN74LS595 and the ULN2803 sink drivers, if you can get them.
By daok
#66529
:)

Ok. I fixed the Resistance location and the resistance Ohm.

Image

I do not understand why the Shift Register at #3 should be removed. How can we will tell in the code later which row to light up?

I haven't order yet the Shift Register and the Sink Driver but I plan to do it today. I will go with your suggestion but I just want to understand... the 74HC595 do not drive enought current if I understand well the last message but in the Spec sheet I see it drives up to 20ma, see below:

Image


For the 5v and the 40ma that is not enought because it requires 80 by Matrix, do we will need some capacitor or something that can hold and release more current (you must laugh on this one but I try to find some solution :D)
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By FartingMonkey92
#66530
It's the sink drivers that we use to ground each row of LEDs... One row after another.
So you could move the sink driver to where number 3 was, but keeping the connections in the latest image.

Now with the current ratings, it seems as if i'm very confused... :lol:
The datasheet says it 6ma output drive at 5V.
But you can only draw a maximum of 70ma with the whole chip on.
Don't buy any chips just yet. :wink: I've gotta have a think...

To drive this whole thing, you will need a completely seperate power supply. Sparkfun have a tutorial about breadboard power supplies somewhere...
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By FartingMonkey92
#66534
Now i'm thinking each channel can handle 35ma... :roll:
The clamp current is what the integral diodes can handle... Don't worry about that.
I'm sorry for my confusion! :wink:
By daok
#66539
No problem :P I won't buy any chip until you sure of everything, no rush :) I am learning a lot in this process.

Here is the graphic updated (with all what I have understand of the lastest message... i might not understand all but I think it's not too bad :P).

Image

I have found few beginner lesson here at Sparkfun. I will read them tonight, this way I might be less lost :wink:
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By FartingMonkey92
#66540
Thats looking good!
What many forget is that the ULN2803 sink drivers can only connect thier ouputs to ground, datasheets for them don't make this clear to beginners. :wink:

And that is the tutorial i was thinking of.

Have you caught on with the whole concept of how to drive these displays?
By daok
#66543
I understand that with Arduino we will program something that will send Output to some pins. This will light up specific columns ( all leds... well the 8 leds we have in each colums ) and on the other side we will sink the current of some specific rows. This way, by lighthing up and sinking we have a cross operation that let us open specific led. By doing this very fast over all columns our eyes will not see that we are looping through all colums and rows very fast and we should have a good display. Do I understand well the concept? :D
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By FartingMonkey92
#66545
Well done! :D
Offtopic, what time zone are you in?
By daok
#66565
I am from Canada and I am on (GMT-05:00) Eastern Time (US & Canada). It's now 1pm.
User avatar
By FartingMonkey92
#66616
The components you selected earlier should work.
Shift Register 8-Bit - 74HC595, Darlington Driver 8-Channel ULN2803
If you get them elsewhere, make sure you buy them in a DIP, "dual-inline pins", package so that you can plug them into the breadboard. :wink:

A further thought about the chips:
The '595 has a maximum continuous current of 70ma per chip, ~8-9ma but they should work perfectly fine at 10.

Any updates?
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