making a moving, wirelessly controlled led display - led scrolling display

Introduction over the past few years, I have used LED matrix displays for many different projects.
These 8x8 LED units have a controller that allows Arduino to talk to them and send text or graphic information that can be displayed in many ways.
These small units can be daisy.
Link together to create a long scrolling display.
See the video on YouTube that shows the display unit and many other LED display items.
While these displays are visually appealing and easy to use, they may not get the attention that people would like to draw at the fire show or other public fire show.
With this in mind, I decided-
Display using a board column of three 8x32 LED boards.
Each board is installed on the car and three boards are connected together to create a long scrolling message board.
In order to make things more interesting and attract tourists, you can change the information of the display remotely with your mobile phone or computer.
My first set of modules is installed in three small G-scale ore cars. My latest G-
The scale is mounted on each of the two box cars with two modules.
To make it visible from any angle, the display is copied on the back of the box car.
No matter where the car is on the layout, it is good for viewing.
There are 8 8x32 modules on the two box cars.
Display units are available from Amazon and other suppliers.
Each module consists of four 8x8 display modules combined on one board.
This makes the connection very easy.
There is a 5-pin input head on the right side of the display and a 5-pin output head on the left.
Connect to the right side of Arduino (
From the front)
Additional modules are attached to the left.
Connection is VCC-
5 v GND-ground DIN -data in -
Arduino pin 11 CS-chip select -
Arduino pin 10 CLK-clock -
The Arduino pin 13 display is not as bright as it was when delivered.
To increase the contrast, I always cover these displays with transparent red acrylic or red plastic tape.
To maintain the size and weight, I chose plastic tape for installation.
I bought it on eBay.
The two photos show a huge difference in contrast when a piece of red acrylic is placed on the display.
The temperature here (75°F)
I can hardly see it on my workbench.
Even in bright areas, red acrylic makes the display completely readable.
Any variant of Arduino should work.
I chose to use Pro Mini and Nano in my 2 projects as they are much smaller than UNO and many of its brothers.
This schematic shows the Pro Mini-
In addition to the position of some pins, the wiring of the Nano is the same.
Three libraries need to be installed.
They are _ max72 xx-
MD_Parola -
MD_KeySwitch -
(note -
The KeySwitch Library is saved from the scrolling example and is not required.
I left it there because some of the remaining code I modified would not compile unless it was there. )
The Arduino sketch I put together consists of code from multiple sources, including sample Parola Scrolling from the md _ Parola Library.
The library allows you to select the direction of the module and works very well with 4 chopping boards.
In order to configure the library for these boards, you must edit one line in the library.
The file that must be edited is called md_max72 xx.
On my Windows computer, I found this library in the directory below.
User/dave/documentation/arduino/Library/md _ max72 xx-
Master you can find it in another folder.
When you find the file, change the line that reads the definition use_fc16_hw 0 to define use_fc16_hw 1. Save the file and restart the Arduino IDE.
The software allows you to enter a new message from the Arduino terminal as shown below. In addition to entering text, you can also enter commands that change the scroll speed, scroll direction, and some other content.
Scroll direction-
Enter/r again to return normal scrolling speed-
Input/s, where is the number from 0 to 9-
Enter/s0 provides the fastest rolling speed and/s9 provides the slowest rolling speed. (
Please note that/s9 is very slow and cannot be undone unless scrolling once at this speed)Reverse display-
Input/I change the display on the black background from red to black on the red background.
Enter again to return to normal. Set brightness-
Input/B, where is the number from 0 to 9
When/b9 is brightestReset Arduino-the input/b0 gives the dimest display
Enter/x this performs a hardware reset. If the device is plugged into the computer, the message displayed on the display can be edited from the sketch or changed from the Arduino terminal.
I found it tedious because I wanted the whole unit to move on the train.
To change the message, I have to stop the train, connect the Arduino to the computer and change the message.
Remote wireless solutions are required.
I have considered three different ways to connect wirelessly to a mobile train: WiFi, Bluetooth and a pair of RF transceivers.
WiFi is certainly feasible, but there is a big drawback that makes it no longer considered.
WiFi is required in order to use the WiFi.
In some public places (
Hotels, science centers, etc)
WiFi is not on or available.
In this case, I chose two simpler wireless options, Bluetooth and HC-12 transceivers.
Bluetooth is the easiest and cheapest wireless option.
I added a simple Bluetooth board to the Arduino, which controls the display only through three connections, vcc, and the Rx to the Arduino with txd.
Note that you need to temporarily disconnect the Bluetooth txd pin on the Arduino rx pin for programming the Arduino.
The Bluetooth module I use is from Amazon (see: )
The Bluetooth module can be accessed from a mobile phone, tablet or PC with Bluetooth functionality.
Before proceeding, make sure to pair with the train's Bluetooth module using the device setup utility.
On my android phone and tablet I used the free Bluetooth terminal program from Kai Morich
See start using the app to touch the menu bar in the upper left corner and select Settings ".
Make sure you change the send line break to LF as shown below.
Next, transfer to the Bluetooth device in the same menu.
You should see the device you paired.
My Bluetooth adapter is called AMAZON06A and can be seen here-
Select your device and go back to the home screen.
Click on the icon I circled in yellow and you should connect to the Bluetooth device.
Now you can enter the new text you want to display.
Commands can also be entered (
See these instructions under the software)
The command shown here changes the brightness to the maximum (/b9).
One of the best features of this terminal application is its ability to store and send canned text, called macros.
In this screenshot, 10 different macro keys are displayed.
If you hold your phone or tablet vertically, only 6 macro keys are displayed.
If you press and hold one of the macro buttons, you can edit the above.
In this example, I replaced M1 with my name.
Each of the two G
There are four holes on the side of the Scale box car that can accommodate 4 LED modules.
I cut these holes with a laser cutter, but can also be cut in a more traditional way.
Each vehicle has been cut four holes, providing space for 4 modules on each side that display the same information.
Wiring is shown.
Please note that only one 5 conductor cable is used between cars.
As you can see, wiring is not complicated.
The first photo shows the Arduino Nano (
Circled in yellow at the bottom of the car)
Bluetooth module (
Circled in yellow and mounted to the rear of the car)
And battery (circled in red).
You can also see the magnet sticking to the corner block of a fixed roof
There is a magnet in the corner opposite.
This view shows all four modules.
The yellow, orange and black cables running the length of the car power the second box car.
This is the left-hand box car.
The Boxcar display can be powered in many ways.
The simplest thing is to use a 3.
7 V lithium ion battery. I got a 3.
I got a 18650 phone from Amazon with 5 hours of running time.
The battery has a built-in protection circuit to prevent it from being overcharged or discharged.
The batteries I purchased do not have welding labels, so you will either need to weld the wires to them (
Not recommended, but that's what I did)
Or put them in the cell.
You can use 4 NiMH or NiCad cells to provide 4.
8 V, or you can use a higher voltage battery to reduce it to 5 V via a step-down converter.
Another option is the battery pack used to charge a phone or other device.
Getting power from the track is also an option.
Since Arduino and LED modules are sensitive to anything other than the electric "clean" power supply, a filter circuit is needed to track the power supply smoothly and correctly.
Whatever you use, keep in mind that when a long message is displayed, 8 display units can easily draw more than 1 amp.
This can be mitigated to a certain extent by using brightness adjustment (see /b above)
And dim the display.
In order to increase the running time, you can also place several batteries or batteries at the same time.
I found some issues with the dual monitor on G-
Truck truck.
Since these two display sets are connected in parallel, I theoretically think that there may not be enough signals for each display.
A buffer circuit is designed and added on both monitors.
The circuit that uses only two 7404 ICS is shown here.
The buffer is built on a board.
This is the rear view of the buffer board.
I plan to do more experiments with the HO version of this project.
It seems possible to install the display unit back to back on HO gondola or tabletcar.
The challenge may be to power and power the Arduino and Bluetooth modules.
Weight and balance can also be a problem.
If I am lucky, I will definitely leave a note in the comments.
I hope you have the opportunity to build a version of this project for yourself.
Please let me know if I can help.