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DOT-matrix display(LED matrix) points for a good design.
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post10 May 2008 12:17   DOT-matrix display(LED matrix) points for a good design.
hello to all!!!i have a problem please help me.
Im new to Dot-matrix, i only had a byte of knowlegde on 8x8 dot matrix, and now im planning to use a dual Dot-matrix..
im using 8051 microcontroller(at89c2051), and now my problem is designing a Dual-matrixdisplay..
please suggest me a good circuit configuration,that would be capable, if i extend my 8x8 or shall i say a multiple 8x8 dot-matrix. i encountered shift register....but i dont know yet its limitation. or a link for any good dual dot matrix.
regards..
im also thinking that the shiftong of my display, would be handle more on the harware part...but not much connection...its because, for my processor to be efficient(if a hardware can do a thing, let the harware)
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huzaifahm



Joined: 18 May 2008
Posts: 16
Helped: 7
Post18 May 2008 17:44   Re: DOT-matrix display(LED matrix) points for a good design.
Visit http://www.sparkfun.com/datasheets/Components/FYM-20881ABxx.pdf for a datasheet. It is just one of many dual-color matrices available.

If you have driven a single color matrix. What you need to do first is drive 2 or three at once. You should use 74595 shift register to input data to columns and use 7445N to select rows using 1/8 scanning method.

Then for the dual color, scheme is the same except, in single color you had one 74595 for each matrix, now you will have two. 4094 is much better than 74595 for driving dual color matrices.

Let me know if you need further help.
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post19 May 2008 16:05   Re: DOT-matrix display(LED matrix) points for a good design.
Hi leoren_tm,
I don't know exactly what do you want (what means the "dual Dot-matrix") but I'm attached here my old projects about this thema. These are using at89c2051 and 6 or 8 pieces of 7*5 LED dot matrix modules. I think the 7*5 is enough but it's easy to modify the circuits and the programs to 8*8 matrix.
For this projects I'm used Proteus because it can be simulate the circuit, if you don't have it, the circuit screenshots are also included.
Study first the original PDF from ELEKTOR (included in the folder ORI in the zip), this was also my start point.

Hope this helps
zuisti

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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post20 May 2008 12:48   Re: DOT-matrix display(LED matrix) points for a good design.
huzaifahm wrote:
Visit http://www.sparkfun.com/datasheets/Components/FYM-20881ABxx.pdf for a datasheet. It is just one of many dual-color matrices available.

If you have driven a single color matrix. What you need to do first is drive 2 or three at once. You should use 74595 shift register to input data to columns and use 7445N to select rows using 1/8 scanning method.

Then for the dual color, scheme is the same except, in single color you had one 74595 for each matrix, now you will have two. 4094 is much better than 74595 for driving dual color matrices.

Let me know if you need further help.

i already try it...can you suggest an IC, that would be lest components needed and low cost? my problem realy is finding and IC, other IC could do that, but with some resistor and darlington pairs...etc

Added after 2 minutes:

zuisti wrote:
Hi leoren_tm,
I don't know exactly what do you want (what means the "dual Dot-matrix") but I'm attached here my old projects about this thema. These are using at89c2051 and 6 or 8 pieces of 7*5 LED dot matrix modules. I think the 7*5 is enough but it's easy to modify the circuits and the programs to 8*8 matrix.
For this projects I'm used Proteus because it can be simulate the circuit, if you don't have it, the circuit screenshots are also included.
Study first the original PDF from ELEKTOR (included in the folder ORI in the zip), this was also my start point.

Hope this helps
zuisti

dual Color( red and Green) about elektor...i already read that topic...thanks.
im not using proteus, but can i ask info on ISIS??
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huzaifahm



Joined: 18 May 2008
Posts: 16
Helped: 7
Post20 May 2008 12:57   Re: DOT-matrix display(LED matrix) points for a good design.
using 74164 and ULN2003 for driving columns is the cheapest method available. You can also look for maxim led driver here http://www.maxim-ic.com/appnotes.cfm/an_pk/1033
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post20 May 2008 13:00   Re: DOT-matrix display(LED matrix) points for a good design.
i read about max6969...its a good IC, but it cost $1.6 or close...bad design..
but its needs components like resitor on each line right?
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huzaifahm



Joined: 18 May 2008
Posts: 16
Helped: 7
Post20 May 2008 13:09   Re: DOT-matrix display(LED matrix) points for a good design.
well resistors are always there Razz
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leoren_tm



Joined: 19 Dec 2005
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Location: Silicon valley
Post20 May 2008 13:14   Re: DOT-matrix display(LED matrix) points for a good design.
as you said about maxim...its a direct drive(without resistor) Very Happy
but it cost..maybe somewhere there is one cheap/...Razz
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post20 May 2008 16:01   Re: DOT-matrix display(LED matrix) points for a good design.
Hi 'leoren_tm',

1. Thank you for the points Neutral

2. Sorry for my mistake about dual - dual color display Crying or Very sad

3. I'm attached now a zip contained datasheets of several driver ICs used by me.

For example try (also) this one: TCA62746 from Toshiba. This is a 16bit reg, the current value of the 16-output is configurable using one external resistor (!).
There are also cheaper type, this is a family...

Highly recommended to use a shift register with output latches only, for the proper (high enough) refresh rate.

At least at my mind ...
Cheers
zuisti

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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post21 May 2008 12:37   Re: DOT-matrix display(LED matrix) points for a good design.
lol....i didnt give you yet a point...thats was just a help point..anyway...ill try scan you notes..thankyou
may i ask...do you design led display?

Added after 33 minutes:

zuisti if you realy need the points..i can give you...
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post21 May 2008 16:56   Re: DOT-matrix display(LED matrix) points for a good design.
Hi;

> do you design led display?
Yes, but only one-color, and only in Proteus (ISIS), using AVR and PIC uCs.
However, my friends have builded my projects yet (with my help), are working as well.

A'propos Proteus:
> im not using proteus, but can i ask info on ISIS?
Yes, of course (also in a PM). Anyway, Proteus from Labcenter is an electronic CAD program (http://www.labcenter.co.uk/index.cfm), ISIS is the schematic and simulation (also VHDL) part, ARES is its PCB part. It's great !!

> if you realy need the points..i can give you...
No, thanks Neutral

Cheers
zuisti
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post22 May 2008 12:52   Re: DOT-matrix display(LED matrix) points for a good design.
i read about the datasheets..anyway im still trying to get the components...
does proteus support MCU programming?
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post22 May 2008 16:13   Re: DOT-matrix display(LED matrix) points for a good design.
leoren_tm wrote:

does proteus support MCU programming?


Yes, 8051, AVR, ARM, PIC10-12-14-16-24, Basic Stamp, also source level debugging (C, Basic, ass), embedded assemblers for sw developing, with real periferies: hc164 ... hc595 shift regs, 5*7 and 8*8 LED matrix displays, char and graphics LCD, keyboard, real rs232 and USB simulation too ....
Look at the homepage!
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
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Location: Silicon valley
Post23 May 2008 12:50   Re: DOT-matrix display(LED matrix) points for a good design.
realy? im using pr*tel...what does basic stamps mean??
if you design in proteus, you dont need to have a hexfile generator? or something like keil?
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post23 May 2008 15:46   Re: DOT-matrix display(LED matrix) points for a good design.
Hi;

> what does basic stamps mean??

http://www.parallax.com/Default.aspx?tabid=295

See the attached picture, it's a screenshot of a simple Proteus Basic Stamp demo project (you can download a working Proteus demo from their homepage).

> if you design in proteus, you dont need to have a hexfile generator? or something like keil?

If you are programming in assembly, Proteus has assemblers for many uCs to make the proper hex files, and you can it assign ('download, burn') to the uC.
Anyway, you can use also a lot of C compilers like Keil.

http://www.labcenter.co.uk/products/vsm_overview.cfm
and
http://www.labcenter.co.uk/products/compilers.cfm

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leoren_tm



Joined: 19 Dec 2005
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Location: Silicon valley
Post23 May 2008 22:53   Re: DOT-matrix display(LED matrix) points for a good design.
ah.ok..
back to my project...how can i elimanate shadowing? im driving my collum with a shiftregister,with latch and my row with 7port and a transistor,,
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post24 May 2008 6:44   Re: DOT-matrix display(LED matrix) points for a good design.
i just try some shift register...but now my problem is, brigthness control...do you know some IC to control the voltage by some input? or has a function on PWM?
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humber



Joined: 21 Mar 2006
Posts: 56
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Post24 May 2008 12:09   Re: DOT-matrix display(LED matrix) points for a good design.
Shadowing is often caused by a slow multiplexer - the driving transistors do not switch fast enough to avoid overlap between the displays or segments. Generally, it will be that the driving transistor switches off too slowly, rather than on.
Check this with a scope, or try to minimise the base drive impedance.
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
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Location: Silicon valley
Post25 May 2008 1:14   Re: DOT-matrix display(LED matrix) points for a good design.
"base drive impedance"
cayou explain it futher? i think shodowing could be elimated by blanking...by means of your sofware..
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post28 May 2008 14:20   Re: DOT-matrix display(LED matrix) points for a good design.
leoren_tm wrote:
"base drive impedance"
cayou explain it futher? i think shodowing could be elimated by blanking...by means of your sofware..

Hi;
I agree with you, leoren_tm. The shadowing is caused (almost always) by the software timings. The advantage of multiplexing is also a disadvantage in this case. But ... do not use blanking, it may be cause more flickering. Use delay routines before any scroll and/or a little slower scrolling speed instead!

The "minimising of the base drive impedance of the row driver transistors" is also important, but far not so considerable for eliminate the shadowing. The delay caused by the saturation 'symptom' is far shorter as the program execution timings, at least at my mind.
Take care!
zuisti
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huzaifahm



Joined: 18 May 2008
Posts: 16
Helped: 7
Post29 May 2008 10:23   Re: DOT-matrix display(LED matrix) points for a good design.
leoren_tm wrote:
ah.ok..
back to my project...how can i elimanate shadowing? im driving my collum with a shiftregister,with latch and my row with 7port and a transistor,,


This flickering can be removed in programming. Following is the pseudo code I follow:

For rows 0 to 6{
FillColumnBuffer(rowID)
TurnOFFRows(all)
ClockDataInCols()
TurnOnRow(rowID)
Delay()
}
You will have to be accurate about delay. And donot process anything else when clocking data in. You have to minimize the time between turning all rows OFF and turning the next row ON.

Regarding brightness control, You will have to introduce PWM of some sort, which will give 1 to each row in pulses. Usually, Instead of pulses, I turn each row on fully for like 8ms(assumed value) and then I turn off all rows. When you introduce PWM, it will use the same 8ms time, but instead of putting row ON full time, it will send pulses to turn leds on and off. The more the pulses, the lesser the brightness. That is why without using PWM will have the most brightness.

Do you need anymore help?
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post31 May 2008 10:24   Re: DOT-matrix display(LED matrix) points for a good design.
Quote:
Do you need anymore help?

i realy need help. i just made my prototype but i have now problems...i could not reach the required voltage, that is why its dim...i have problem on my row driver(5x7)...im using a darlington pairs, can you suggest a flowdiagram? and im coding it on assembly.
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huzaifahm



Joined: 18 May 2008
Posts: 16
Helped: 7
Post31 May 2008 12:44   Re: DOT-matrix display(LED matrix) points for a good design.
Follow this:

http://attiny.com/dotmatrix.htm

I will post some technical talk later after you have reviewed above website.
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aderich



Joined: 03 Jun 2008
Posts: 8
Post03 Jun 2008 21:03   Re: DOT-matrix display(LED matrix) points for a good design.
i will think it to be a simple manipulation of the previous circuitry.
the use of a 748cf95a shift vregister will give a clear guide to your quest
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post04 Jun 2008 12:41   Re: DOT-matrix display(LED matrix) points for a good design.
huzaifahm wrote:
Follow this:

http://attiny.com/dotmatrix.htm

I will post some technical talk later after you have reviewed above website.


quiet busy..ill read it and ask some question..thanks man..
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qingwei_cui



Joined: 07 Jun 2008
Posts: 1
Post07 Jun 2008 5:26   DOT-matrix display(LED matrix) points for a good design.
thank you for your share
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zuisti



Joined: 02 Jul 2004
Posts: 48
Helped: 2
Post07 Jun 2008 8:14   Re: DOT-matrix display(LED matrix) points for a good design.
My MMD project (working in Proteus ISIS) was upgraded for char scrolling (switchable, the speed too), the source is converted to C (MikroC) and PicBasic (Proton+) too.
A newer ZIP is uploaded by me:
http://www.edaboard.com/viewtopic.php?p=1035838#1035838

Last edited by zuisti on 08 Jun 2008 8:53; edited 1 time in total
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raghun



Joined: 19 Jan 2006
Posts: 10
Post08 Jun 2008 7:06   Re: DOT-matrix display(LED matrix) points for a good design.
where can i tutorial about led matrix display
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leoren_tm



Joined: 19 Dec 2005
Posts: 591
Helped: 19
Location: Silicon valley
Post09 Jun 2008 7:02   Re: DOT-matrix display(LED matrix) points for a good design.
after reading it..i was confuse on how did you display a running text??
at what part of it? if displaying it 20times....uhmmm...if your displaying a running text, you would have a problem if it would be design on just accepting a character...and display it...and did you map it??why ASCII??how did you do it?
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sohail_akram



Joined: 26 Feb 2006
Posts: 50
Post12 Jun 2008 6:22   Re: DOT-matrix display(LED matrix) points for a good design.
THis is bundle of moving message circuits and softawres

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