Large Scoreboard LED Displays

[Mark]

Looking for idea's on the design of a large 3 -Digit, 7-Segment LED
outdoor display scoreboard. The unit needs to be about 10 Metres away
from the Microprocessor running things, I am uring towards discrete
LED construction because of price, would like something like a
two-wire interface (except power (I2C my preference)) any pointers
would be appreciated.
Mark in Spain
[email protected] (remove the X to reply)

 

[John Fields]

Looking for idea's on the design of a large 3 -Digit, 7-Segment LED
outdoor display scoreboard. The unit needs to be about 10 Metres away
from the Microprocessor running things, I am uring towards discrete
LED construction because of price, would like something like a
two-wire interface (except power (I2C my preference)) any pointers
would be appreciated.

 

[Dan Hollands]

I would suggest using an RS485 datalink instead of I2C to improve noise
immunity over the 30 meters

Dan

--

Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
[email protected]
www.QuickScoreRace.com

 

[Bob Eldred]

Looking for idea's on the design of a large 3 -Digit, 7-Segment LED
outdoor display scoreboard. The unit needs to be about 10 Metres away
from the Microprocessor running things, I am uring towards discrete
LED construction because of price, would like something like a
two-wire interface (except power (I2C my preference)) any pointers
would be appreciated.
Mark in Spain
[email protected] (remove the X to reply)

If I understand what you are asking, you will need ten lines for this to do
it directly with no electonics at the display, 11 with a decimal point. The
lines are: 7 anode drivers (segments) and three cathode drivers. The drivers
need to supply the required LED current which may be 100mA or more depending
on type and brightness, plus if you series LED's to make large segments
(rows of LED's), you'll need more voltage depending on the the number of
LED's. Since you are only going 10 Meters and since it's a visual display,
the speed of operaton is not important so you don't have to worry about
terminating the lines or any other high frequency effects. I don't think I2C
is necessary or even appropriate since you would need electronics at the
receiving end. If you want to do it with a single serial wire pair you'll
need electronics at the receiving end plus power. RS232 without any
handshaking directly to and from the micros built in UARTs would be the
easiest. But, I wouldn't do that for 10 Meters, I'd just run a 10 conductor
cable, 20 AWG or something. You will need driver transistors to get the
required LED current and voltage. All of the electronics and power would be
at the control point with nothing but the LED's at the board. Keep it
simple.
Bob

 

[Mark]

Looking for idea's on the design of a large 3 -Digit, 7-Segment LED
outdoor display scoreboard. The unit needs to be about 10 Metres away
from the Microprocessor running things, I am uring towards discrete
LED construction because of price, would like something like a
two-wire interface (except power (I2C my preference)) any pointers
would be appreciated.
Mark in Spain
[email protected] (remove the X to reply)

Update, I was looking to make the 3 digits all run from 4 wires (2 for
supply 2 for control signals) to keep the interconnecting wiring down
to a price. The unit does not have to run a lightning speed, it will
only be updated every 250ms or so. The size I am looking to achieve is
about 300mm high, so each segement would have about 16 LED's (dual
row). I write all my code with PicBasic Pro, so the easiest
communication protocol with this software is preferable. The supply
voltage to the unit can be either 5V or 12V, both are available.

 

[Ross Herbert]

Looking for idea's on the design of a large 3 -Digit, 7-Segment LED
outdoor display scoreboard. The unit needs to be about 10 Metres away
from the Microprocessor running things, I am uring towards discrete
LED construction because of price, would like something like a
two-wire interface (except power (I2C my preference)) any pointers
would be appreciated.
Mark in Spain
[email protected] (remove the X to reply)

Is this the sort of thing you are looking for?
http://www.siliconchip.com.au/cms/A_103978/article.html

 

[Ross Herbert]

Is this the sort of thing you are looking for?
http://www.siliconchip.com.au/cms/A_103978/article.html

PS.

You will probably find that this link will not provide the full
article - which is in 2 parts by the way. To overcome the need to pay
to receive the full article/s I have discovered that if you use Google
and type <sports scoreboard silicon chip> into the search window the
first two results will provide links to the full article/s.

 

[Mark]

I'm now thinking along the lines of Micro end feeds out I2C straight
into MAX232. At the scoreboard display end, MAX232 feeds straight into
3x PCF8574 (one per digit with different addresses of course), will
that work?

 

[Tim Mitchell]

I'm now thinking along the lines of Micro end feeds out I2C straight
into MAX232. At the scoreboard display end, MAX232 feeds straight into
3x PCF8574 (one per digit with different addresses of course), will
that work?

No it won't, I2C has a bidirectional data line, MAX232 has separate
transmit/receive. I2C is designed to connect stuff inside a piece of
equipment, not for those sort of distances anyway.

I would suggest using one 74HC595 per digit, which is an 8-bit serial to
parallel chip. You just clock 8 bits into it and wiggle the latch line,
the 8 serial bits then get latched to the 8 output pins.

You can use a ULN2803 (8 way darlington driver) as a power driver for
the LEDs.

You need 3 control lines (Data, Clock and Latch) + power. I would advise
having a Pic or something in the sign, and just send RS232 text to it to
be displayed. The pic can then send the data to the latches. If you use
the right pic it might even have enough I/O pins to drive the segments
directly.

I have made a big LED sign this way (with the HC595) and it works well.