Free Project - 245 LED Display

[iulisan]

Thanks.
Like I said in my previous posts : I think my board is ok cause it's made after magu(zamfirelu http://www.zamfirelu.org/dtpt/viewtopic.php?t=254) schematics , and a read over and over again the whole thread...the problem is that I can't connect with the computer to the board and today i saw that even when the eeprom in not present on board , the LED for programing blinks the same like with the eeprom on it.
Again thanks a million.
P.S. : I contacted magu on his forum and i stand in touch with him last year , when i first begun to build the display , but until now he did not respond to my new posts , so that is why I decided to post in this forum that started all...
P.P.S. : I'm impatient to continue the project because in this period I have time to do so.

[iulisan]

Yep it's working...Bill G. made me some crazy days with his xp...

[charudatt]

Nice to read posting on this project in the year 2008.

I am about to start with the project with certain modification on the PCB.

I don't wish to drag the project on.... and on.... but , just wanted to make sure, i don't do the same mistakes (if there are any).

Shall post my modified schematic shortly.

regards

[T.Jackson]

This thread has certainly had some hits. Source code downloaded over 2,500 times!

[Ioannis]

Sure is a "hit"!

Also congrats for your new article on EPE!

Ioannis

[T.Jackson]

Sure is a "hit"!

Also congrats for your new article on EPE!

Ioannis

Thanks Ioannis.

But I must say that I'm a little disappointed with EPE at the moment though. They have banned me from their forum for saying the following things ...

a. The burglar alarm is mediocre, certainly not "ultimate" like originally publicized.
b. Freelance technical engineering for magazines pays very poorly.
c. I have no plans on submitting anymore projects to SC.

So don't expect to go onto EPE's forum and ever speak openly about anything, because chances are they'll suspend your account and delete your posts.

Not happy

[Ioannis]

I have followed your very good publications up to this moment. I must say that all are excellent.

Too pity that you had such a treatment.

Don't give up. There are other publishers still. If like what you do, I am sure you 'll get the recognition you deserve. And you really do.

Ioannis

[T.Jackson]

Too pity that you had such a treatment.

As Melanie likes to say; "any resemblances between persons living or dead is purely coincidental"

[Ioannis]

Good one!

Ioannis

[Bronx68]

Please explain the use of D3 through D7 do make an 'or gate' for reset. Why 100K resistors?
Why not use Q0 from each of the CD4017 counters?

[falingtrea]

Please explain the use of D3 through D7 do make an 'or gate' for reset. Why 100K resistors?
Why not use Q0 from each of the CD4017 counters?

The diodes are used to create a master reset from the PIC and to isolate each 4017's reset from each other. Diodes are usually a lot cheaper than logic for something as simple as this. The 100k is probably on the conservative side as far as a value, unless the designer was trying to reduce race conditions or output glitches by creating a simple RC filter.

[T.Jackson]

The diodes are used to create a master reset from the PIC and to isolate each 4017's reset from each other.

Correct!

Further explanation -- without the diodes intact, Q0 lines on the counters wouldn't have control over their designated MR line. You simply can't tie all the Q0 lines together with anything but a semiconductor for this. As for the 100K resistors -- these ensure that there's never going to be a short between RB5 on the PIC and associated Q0 lines on the counters. When RB5 swings high, any of the Q0 lines on the counters could be either high or low. This is CMOS we're talking about here, we could even go as high as a mega ohm.

[inspired4real]

HELLO T JACKSON, YOUR PROJECT IS INSPIRING AS IF TO SAY CHALLENGING SO MANY PEOPLE AROUND THE WORLD. I WANT TO BUILD THIS PROJECT AND MAGUS SITE TENDS NOT TO OPEN AND IT IS LIKE IT IS NOT IN ENGLISH(SORRY TO MAGU IF I AM WRONG). I AM THOUGH A NEWBIE TO PIC IN SOME SENSE BUT HAVE BEEEN PLAYING WITH ANALOG ELECTRONICS FOR SOMETIME. WHAT I DONT REALLY UNDERSTAND IS THE EEPROM ASPECT OF YOUR PROJECT, I WANT TO KNOW HOW YOU LOAD THE ASCII CHARACTER SET INTO THE EEPROM FROM YOUR PROGRAM, OR ARE YOU NOT USING THAT METHOD. I WAS THINKING OF DEFINING EEPROM ADDRESSES FOR ASCII CHARACTER AND THEN LOADING EACH CHARACTER IN AN ADRESS THAT I WILL LATER READ TO DISPLAY CHARACTER. DO YOU HAVE ANY DETAIL MATERIALS ON HOW TO USE EERPOM LIKE THE ONE YOU USED IN THE PROJECT? HOW FAST REALLY DO YOU FETCH DATA FROM THIS EEPROM . I AM THINKING OF BUILDING A BIGGER DISPLAY USING 3mm ULTRABRIGHT LED WITH BUFFER AND SUPPLYING ABOUT 50ma OF CURRENT WITH MULTIPLEXING I DONT THINK THE LEDS WILL GET DAMAGED? SORRY REALLY IF MY QUESTION MAY BE TOO SIMPLE FOR YOU TO REPLY TO?
IS THERE ANYWAY I CAN GET MAGU'S LINK AND DOWNLOAD HIS STUFF. THANKS.

[T.Jackson]

The ASCII characters are custom, specific only to this project. They are programmed into the eeprom one byte at a time, whereas each byte represents data for the column in the character. Each column of data for a character is assigned a unique address in the eeprom and all the columns are collated together to form the character. It is impossible to explain the entire inner workings of the system in just a few paragraphs. I don't recommend this project for anyone who is new to pics / electronics.

Regards,

Trent Jackson

[Bronx68]

Trent,
I am also designing a similar scrolling sign. I am storing the entire character set in the PIC program memory. I then plan to fetch the characters out by switches to build a buffer that contains the message. Any insight on this approach? Did you look at this approach?

[T.Jackson]

Give me a 100 engineers and I'll give you 100 different solutions to the problem. This kind of project is really quite abstract, my solution is far from the best and or the cheapest. I haven't really explored other possibilities well enough to make any suggestions. Using single sided PCBs was a silly thing to do (this is why it wasn't published)

Regards,

Trent Jackson

[inspired4real]

Hello Jackson, I Have Built This Project Before Using The Pic Code Space For Storing My Character Defintion, But The Message Had To Be Fixed And Each Time I Had To Reburn The Pic For A New Message To Be Displayed, This Is Where Yours Has Advantage Over Mine. The Only Thing I Have Not Really Worked With Is Eeproms Because I Hardly Find Them Around Where I Live And The Common Ones Close To Me Is The 27c512 Types, Can This Act As A Replacment Even With Modifications, So That I Can Do A Few Breadboarding To See How It Works?
Thanks For The Previous Reply To My Post.

[skimask]

And The Common Ones Close To Me Is The 27c512 Types

A common one close to you is the 27C512? Where are you? In the PC salvage yard from yester-year?

A 27C512 is a 64K x 8 EPROM. Great choice, if you're up to driving 16 address lines, 8 data lines, along with a few control lines, and like to wait around with a UV eraser just to change one byte at a time.

A much better choice would be a 24LC1025, 64K x 8 SERIAL EEPROM. 2 wires, reprogrammable in circuit, probably faster access times...AND PBP supports it with I2CREAD/I2CWRITE.

Not saying that interfacing with a parallel EPROM isn't possible...It certainly is and not really that hard...But WHY?

[T.Jackson]

I believe that the 512 would be a drop in replacement for the 256. Both use word sized addresing and are pin for pin compatiable.

Trent Jackson

[T.Jackson]

Hey Jeremy,

With a 27c256 -- how do you restrict the electron flow to and from the data pins to precisely 33 p/uS? It's probably really simple to do, alas, so am I.

Don't ask me why I need to know, instead perceive it as a completely "abstract" (theoretical) -- sort question.

Trent Jackson

[skimask]

I believe that the 512 would be a drop in replacement for the 256. Both use word sized addresing and are pin for pin compatiable.

A 27C512 is a direct drop in replacement for the 24LC256?
Only with a hammer and a dremel tool...and some of those mushrooms you've got laying around...

[skimask]

With a 27c256 -- how do you restrict the electron flow to and from the data pins to precisely 33 p/uS? It's probably really simple to do, alas, so am I.
Don't ask me why I need to know, instead perceive it as a completely "abstract" (theoretical) -- sort question.

Well, you're a smart guy, all that college edgjamakayshun and the double-naught secret service and all.
You should be able to figure it out.

[T.Jackson]

A 27C512 is a direct drop in replacement for the 24LC256?
Only with a hammer and a dremel tool...and some of those mushrooms you've got laying around...

I made an assumption. I actually thought that he was referring to a 24LC, because given that the micro only has 18 pins -- it's impossible to directly interface it to a 27c without a 4040, 12-BIT, BCD counter (or similar) for the parallel addressing. Even then there would be insufficient IO pins remaining for the rest of the project. On top of that -- playing around with eproms isn't a chore for the beginner. Perhaps I'm totally mistaken.

Trent Jackson

[skimask]

On top of that -- playing around with eproms isn't a chore for the beginner. Perhaps I'm totally mistaken.
Trent Jackson

Neither is playing with PICs, but soooo many think otherwise...
Maybe I'M totally mistaken.

[T.Jackson]

Neither is playing with PICs, but soooo many think otherwise...

I disagree. Languages like PBP makes playing around with PICs a chore for the beginner. But implementing a 27c256 eprom into the equation does require much extra knowledge than the PBP manual can depict.

Trent Jackson

[rele]

Hello members

This is not quite relate with this topic, but I thik it may be usefull.

I need to do increase power suply for led display to +7V - 9V instead +5V wich is now. Row drivers is irf9530 (from mcu thru 1K on gate, +5V sors, drainon led row), and column driver is HC164 + ULN2803.
Instead of irf9530 I try with BD242 (and few others), but if I increase suply on emiter above 5.5V, transistor is fully conductive (colector - emiter), and every led is on. With +5V on emiter everything is ok, but leds are with verry poor light.
When I replace ULN2803 with 8xBS170 (n-fet), I have little better result but still not good enough.
All this is without current limiter ressistors.

Leds are red, 2 leds in series for 1 dot.


Regards

[T.Jackson]

leds are current dependent, not voltage.

Trent Jackson

[rele]

Yes, but here I have two leds in series, and supply of +5V. I have voltage drop of 1.2-1.6 on ULN drivers, and rds on 9530 0.30 ohm. I guess I need to increase voltage?

Regards

Rele

[Ioannis]

Each led could use 2 volts so an increase is recommended.
Ioannis

[yupng]

i need a software and hardware about dot matrix message display using wireless keyboard.
Use wireless keyboard to sent the data to dot matrix message display....
Anyone can help me???
Pls.........

[skimask]

i need a software and hardware about dot matrix message display using wireless keyboard. Use wireless keyboard to sent the data to dot matrix message display.... Anyone can help me??? Pls.........

Don't ask for much do ya...

What is your skill set?

Which PIC do you want to use?

What sort of hardware would you like to use?

What kind of wireless transmission protocol are you planning on using?

Lost yet?

Try eBay...

[yupng]

Don't ask for much do ya...

What is your skill set?

Which PIC do you want to use?

What sort of hardware would you like to use?

What kind of wireless transmission protocol are you planning on using?

Lost yet?

Try eBay...

What i want is use two microcontroller(MCU) to build this project. One MCU is connect to PC keyboard and transmitter(using RF or IR to transmit the data).Another MCU connect to receiver(can be IR or RF circuit) and dot matrix. I found one similar project but i cant found the datesheet for the MCU used in this project. I also don't understand the code.

[skimask]

What i want is use two microcontroller(MCU) to build this project. One MCU is connect to PC keyboard and transmitter(using RF or IR to transmit the data).Another MCU connect to receiver(can be IR or RF circuit) and dot matrix. I found one similar project but i cant found the datesheet for the MCU used in this project. I also don't understand the code.

And didn't answer ANY of the previous questions...

[yupng]

And didn't answer ANY of the previous questions...

i still doing the research for this project. So i not confirm what hardware are require for this project. I hope anyone has this similar project can post it to me. Actually my project topic is <Wireless Announcement Board>.
Any information that related to this project also can post to me.
Thanks.......

[skimask]

i still doing the research for this project. So i not confirm what hardware are require for this project. I hope anyone has this similar project can post it to me. Actually my project topic is <Wireless Announcement Board>.
Any information that related to this project also can post to me.
Thanks.......

I'd doubt anybody can help you until you help yourself.

Until then, sounds like you might want to use something prebuilt:
http://www.sparkfun.com/commerce/pro...roducts_id=760

[yupng]

I'd doubt anybody can help you until you help yourself.

Until then, sounds like you might want to use something prebuilt:
http://www.sparkfun.com/commerce/pro...roducts_id=760

I had done this project before but not with wireless. I use RS232 port sent the data from pc to dot-matrix display module. Now, i need to improve it to be wireless.
The problem is :
How i send out the data via wireless.
How to translate the receive data and display it on dot-matrix display module.

Anyway........thanks for your reply.
Thanks.......

[mackrackit]

You can use radio modules like these(take your pick)
http://www.rentron.com/PicBasic/RemoteControl.htm
to send serial data.

[yupng]

Anyone can help me do a "wireless announcement board" using dot-matrix.
The data(text) is send out from keyboard via wireless to dot-matrix display.

[T.Jackson]

Anyone can help me do a "wireless announcement board" using dot-matrix.
The data(text) is send out from keyboard via wireless to dot-matrix display.

20k

There's so much psychology in music heh

Trent Jackson

[T.Jackson]

Or would you prefer a 6 million dollar lawsuit?

Trent Jackson