This is an Instructure to build a big (600mm x 400mm)
Scroll LED display.
This is a project that runs in the hacker space of Nottingham, UK, along with instructures.
Instructures sent hundreds of large to hackspace (10mm)
LEDs can play and create something good.
Jack Howe and I decided to use something at the event to promote and highlight the hacker space --
We all have a similar idea to create some kind of presentation, so we decided to work together --
Jack is doing shell and pixel design while I am in charge of electronics and programming.
This time and go to TiVo-Magnetic field (EMF camp)
A hacker and technology-oriented camping festival in the UK.
The end result is a programmable display that runs from 12 v dc and can be programmed to display any title text you want.
Each LED pixel can be merged, so we can also create interesting displays.
Nottingham hacker space has a green theme, so it's natural for us to use green LEDs on this display.
We have about 500 of these LEDs, so we came up with the best and maximum arrangement we can do.
We decided that each pixel would be made up of 4 LEDs that are connected in series with a range of current limiting resistors to operate from 12 v DC.
We decided that the pixel height of 8 would be good (
Mainly due to the eight outputs of each shift register unit)
So the most column we can do is 500 pcs/8x4 = 15.
6, so 15 columns.
Someone used a few green LEDs in another project, which means we can only do 14 columns, and finally we only do 12.
Therefore, our design is 4 LEDs per pixel, 8 pixels high and 12 pixels wide.
This should provide good enough resolution for text and very basic graphics.
We have stock of grilled plywood and plexiglass sheets for 600x400mm.
So we decided to make this unit the maximum size.
Jack Howe began making laser cutting boards with 8x14 pixels.
These all have rounded corners and the end result is a noce effect that looks a bit like people think the future will be like the past (retro-future? . . . . ). The .
The dxf design will be put here.
This part is too boring.
I put 4 LEDs in each pixel.
I then welded them to a ring, one side folded down and added the other side.
The positive of each pixel is welded to the resistance (330 ohms)
Connect together (
The Pixel is controlled by a pnjunction transistor to the ground).
The resistance calculation comes from understanding the voltage and equivalent current of the LED and the supply voltage: 4x2. 1V = 8.
4 V, traffic 10 mA.
Resistance must drop by 12 V-8. 4V = 3.
6 v, the allowable current is 0. 01A to flow.
V = I x R, so R = V/I = 3. 6/ 0. 01 = 360 ohms.
330 Ohm is the closest value I have so we used it.
Run the tracking line from the negative direction of each pixel.
This is controlled by the shift register to control each pixel.
It became very boring after welding 448 LEDs and 112 trailing wires.
Make PCB next time. . . . .
I used a shift register board for sale as a kit for the 7-segment LED display.
This is available here: the board is very basic, using only the 74 hc595 shift register and the UN2003 7 transistor pnp resistor array.
The last pixel is controlled by the pnjunction transistor of BC548, with 8 outputs per board.
With the power of google, there is more information about using the 74 hc595 shift register.
I'm going to use arduino-compatible micro-controllers, so this is very useful: a board is required for each column, so I have to make up 12 boards that are in series.
12 V, 5 V, GND, data, clock and latch are connected to each board.
To control the output, you need to output the data clock to all 96 locations and then set the latch to high
This will switch the entire display at the same time.
This can be done soon.
I'm lying with a single chip microcomputer of AVR us.
This is a digital, USB-only micro-controller.
I have written instructions before about uploading Arduino code to them: this micro-controller becomes the brain of this unit.
Use 3 digital lines: data, clock, and latch.
I wrote a bit of code to get the text and figure out what it should look like (
7x5 wide font)
Then light up the correct LEDs.
This is saved in a frame buffer that moves at a scrolling rate and is uploaded to all pixels each time a change is made.
This can be a bit dense in processing, but it makes the code simple and I can't see any flickering even if the scrolling is very fast. Daniel (
Another hacker space member)
A library was written to organize the text on the matrix.
His example can be obtained from github: these libraries need to be installed to run the following code.
The code can be used as.
Download the zip file here.
This is the unit in action.
The evening looks great, especially at EMF camp, which is used to promote the opening hours of robot cocktail bots built by a small group of Nottingham hacker spaces.
Daniel also upgraded the code to include a space between the text to make it more readable.
The next steps are to make some nice visuals or make some videos with very low resolution. . . .