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Ideas for large LED RGB display (how to drive, etc).

K

klaas langhout

Jan 1, 1970
0
I'm trying to set up a rather large RGB LED display. In specific,
approximately 1000 RGB LED's in a way where I have individual control of ea.
LED (color must have, brightness nice to have).

My current plan (though I need to see if this will work, no previous
experience) is to use a MAXIM MAX7219 serial in/out 8 digit, 8 segment
driver to multiplex 64 LED's for a single color. So, for RGB each panel of
64 LED's will have 3 MAX7219 chips to drive R, G, B separately across the
entire set.

The MAX7219 can be put in series up to 16 so, i'll end up with muliple sets
of 16 to control all 1000 led's.

My question is this, what other methods / ideas do people have to do this.
I just ordered some chips/led's to do some experiementation as i'm not sure
I can PWM the LED's enough to get different shades. One additional note,
I can't use an intergrated LED display as I want the ability to move/space
out the LED's in a custom physical arrangement (e.g. space them out every
1-6 inches).

Any ideas appreciated....
 
D

Don McKenzie

Jan 1, 1970
0
klaas said:
I'm trying to set up a rather large RGB LED display. In specific,
approximately 1000 RGB LED's in a way where I have individual control of ea.
LED (color must have, brightness nice to have).

My current plan (though I need to see if this will work, no previous
experience) is to use a MAXIM MAX7219 serial in/out 8 digit, 8 segment
driver to multiplex 64 LED's for a single color. So, for RGB each panel of
64 LED's will have 3 MAX7219 chips to drive R, G, B separately across the
entire set.

The MAX7219 can be put in series up to 16 so, i'll end up with muliple sets
of 16 to control all 1000 led's.

My question is this, what other methods / ideas do people have to do this.
I just ordered some chips/led's to do some experiementation as i'm not sure
I can PWM the LED's enough to get different shades. One additional note,
I can't use an intergrated LED display as I want the ability to move/space
out the LED's in a custom physical arrangement (e.g. space them out every
1-6 inches).

Any ideas appreciated....

have a look at:
http://www.dontronics.com/micro-vga.html
may be a idea worth considering

Don...


--
Don McKenzie
E-Mail Contact Page: http://www.e-dotcom.com/ecp.php?un=Dontronics

Micro,TTL,USB to 1.5" color LCD http://www.dontronics.com/micro-lcd.html
USB,RS232 or TTL to VGA Monitor http://www.dontronics.com/micro-vga.html
World's smallest USB 2 TTL Conv http://www.dontronics.com/micro-usb.html
 
K

klaas langhout

Jan 1, 1970
0
Cool board and I fully agree that it would be much cheaper / easier to go
with VGA out to an LCD display. I can't do this however as, each LCD
element in what I'm putting together is 6" apart so, I have to go with
discrete LED's. Now, if there were a board that can control a ~ 30 x 30
matrix of LED's (say, a really small LCD display) that I could hack in, that
would be something :)

Cheers.
-------------------------------------------------
 
D

Don McKenzie

Jan 1, 1970
0
klaas said:
Cool board and I fully agree that it would be much cheaper / easier to go
with VGA out to an LCD display. I can't do this however as, each LCD
element in what I'm putting together is 6" apart so, I have to go with
discrete LED's. Now, if there were a board that can control a ~ 30 x 30
matrix of LED's (say, a really small LCD display) that I could hack in, that
would be something :)

small LCD, OK here is another:
http://www.dontronics.com/micro-lcd.html
again, it may not suit your application.

Don...

--
Don McKenzie
E-Mail Contact Page: http://www.e-dotcom.com/ecp.php?un=Dontronics

Micro,TTL,USB to 1.5" color LCD http://www.dontronics.com/micro-lcd.html
USB,RS232 or TTL to VGA Monitor http://www.dontronics.com/micro-vga.html
World's smallest USB 2 TTL Conv http://www.dontronics.com/micro-usb.html
 
K

klaas langhout

Jan 1, 1970
0
Erik, good information thanks.

For the questions:
1) How frequently does each pixel change value? Are you doing static
images, or full 30FPS video? Or is this more like a ballpark scoreboard

- This is for an art piece and, i believe 10fps should provide a good degree
of dynamic image quality. I don't need video quality :
2) How much current do you plan on putting through each LED?

- Only nighttime viewing (no external lighting) so, i suspect 10ma per pin
may be enough.
3) How much are you willing/able to spend per pixel?

- I'm open. for the ATMega48's at $1.69 ea for 6 rgb led's that works out
to $281- for 1k LED's which is still less than the LED's.

~ klaas
 
E

Erik Walthinsen

Jan 1, 1970
0
klaas said:
- I'm open. for the ATMega48's at $1.69 ea for 6 rgb led's that works out
to $281- for 1k LED's which is still less than the LED's.

What system are you going to be using to control these? Whatever it is
that holds and updates the framebuffer is going to have to manage the
240+Kbps datastream, which has to be distributed to each of the
controlling chips. I2C at 400KHz may or may not do it, as you have to
deal with the bus overhead as well as the fact that depending on how the
code is written for the ATmega, it may have to block for short periods
of time, somewhat randomly. SPI would work better, since you can
"broadcast" the data, but you'll have to have buffers to handle that
many devices on the bus.

I don't know how much of this engineering you're planning on doing
yourself, but I'd be interested in at least writing the microcontroller
code (since I need it for another project anyway, and is probably
saleable as a unit), and even engineering the PCBs if necessary. Would
probably put 8 ATmega48's on one board with power and signal buffering,
controlling 48 RGB LEDs each. Headers for flying wires to each LED, or
potentially to a stacked board with spaced LEDs if your spacing
requirements are consistent anywhere.

BTW, the chips drop to $1.56 in purchased q.100 or higher, and you'd
need 167 for 1000 LEDs totalling $260.52. However, depending on the
resulting brightness you might end up needing ATmega88's, which have
twice the Flash space for code (irrelevant here) but can put out 100mA
per group instead of 70mA. The most LEDs on one group will be 7, so
that's either 10mA or ~14mA depending on the chip.

Something else to consider is that depending on how it's all
interconnected, you could easily spend that much money again in
connectors. For instance if you stacked all the boards (for power and
control) and used dual-row 0.1" right-angle headers to connect LEDs one
at a time, you'd use Jameco 203991CE on the board at $0.47 per chip (24
pins), plus 6 4-pin housings at $0.19 each, and 24 crimp pins at $0.07
each. Totals $3.29 in connectors (not counting wire, etc.) per $1.56
chip... If you can solder 4-wire bundles or entire ribbon cables to
each board you'd be a lot better off ;-)
 
T

Terry Given

Jan 1, 1970
0
Erik said:
What system are you going to be using to control these? Whatever it is
that holds and updates the framebuffer is going to have to manage the
240+Kbps datastream, which has to be distributed to each of the
controlling chips. I2C at 400KHz may or may not do it, as you have to
deal with the bus overhead as well as the fact that depending on how the
code is written for the ATmega, it may have to block for short periods
of time, somewhat randomly. SPI would work better, since you can
"broadcast" the data, but you'll have to have buffers to handle that
many devices on the bus.

I don't know how much of this engineering you're planning on doing
yourself, but I'd be interested in at least writing the microcontroller
code (since I need it for another project anyway, and is probably
saleable as a unit), and even engineering the PCBs if necessary. Would
probably put 8 ATmega48's on one board with power and signal buffering,
controlling 48 RGB LEDs each. Headers for flying wires to each LED, or
potentially to a stacked board with spaced LEDs if your spacing
requirements are consistent anywhere.

BTW, the chips drop to $1.56 in purchased q.100 or higher, and you'd
need 167 for 1000 LEDs totalling $260.52. However, depending on the
resulting brightness you might end up needing ATmega88's, which have
twice the Flash space for code (irrelevant here) but can put out 100mA
per group instead of 70mA. The most LEDs on one group will be 7, so
that's either 10mA or ~14mA depending on the chip.

Something else to consider is that depending on how it's all
interconnected, you could easily spend that much money again in
connectors. For instance if you stacked all the boards (for power and
control) and used dual-row 0.1" right-angle headers to connect LEDs one
at a time, you'd use Jameco 203991CE on the board at $0.47 per chip (24
pins), plus 6 4-pin housings at $0.19 each, and 24 crimp pins at $0.07
each. Totals $3.29 in connectors (not counting wire, etc.) per $1.56
chip... If you can solder 4-wire bundles or entire ribbon cables to
each board you'd be a lot better off ;-)

just buy these:

www.monstavision.com

Cheers
Terry
 
K

klaasl

Jan 1, 1970
0
The monstavision won't work: the led's have to have more space between the
;)

I was planning on driving the whole thing with a mini-itx or lapto
equivalent to source the 'image' and send it to the 'display'.

I'm still in the initial r&d phase so not quite sure how much i want to d
myself: the end project is an art display where i want both canne
sequences as well as camera based input. I'm setting up a prototype pane
just to see what the output looks like in full darkness.

The below is good info :)
 
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