Introduction: Display Live Txts on Costume at Party W/ Scrolling LED Belt Buckle

Picture of Display Live Txts on Costume at Party W/ Scrolling LED Belt Buckle
This project shows how to send SMS text messages to a cheap scrolling LED display via an Android app and arduino with USB host shield.

The project was originally inspired by a friend wanting to make a "sexting themed" costume, with a scrolling LED display of live texts sent from people at the party. We found a $13 LED belt buckle online, which looked cool, but only had a few buttons to manually enter in messages. A couple wires and lines of arduino code later, we were able to automate entry of messages.

We then added a host shield and wrote a small Android app to send txt messages on to the arduino.

Step 1: Required Parts and Code

Step 2: Automate Message Entry on LED Display

Picture of Automate Message Entry on LED Display

The display has three buttons that you use to change the messages. It's a long process, since you have to scroll to each letter one click at a time, and there's no speed-scroll. We pop open the case to see if we can easily attach wires to the buttons in order to automate message setting.

The three push button switches simply short the bottom side of the switch to ground when pressed. We're going to simulate this action by switching the bottom side of the swtich between a high impedance pin (a digital input) and ground (a low digital out). This is easily done by switching the direction of the pin on an arduino, using pinMode(pin, INPUT) or pinMode(pin, OUTPUT). Just make sure the output is set Low before setting the pin to output (digitalWrite(pin,0)).

Four wires are attached, three for the switches, one for ground.

Step 3: Wire LED Display to Arduino

Picture of Wire LED Display to Arduino

Use pliers to make a hole for the wires to pass out of the LED display.

Then, attach the black wire (On/Off/Enter) to Arduino Digital In 2, Red (Page Up) to Digital In 3, and Yellow (Page Down) to Digital In 4.

Test out the code by uploading to the arduino, and then opening the serial monitor at 57600bps. Be sure to turn ON 'newline' next to the baud rate setting. The code uses the '\n' character to find the end of words. After you type in a phrase and hit enter, the arduino should fast forward through the same button pushes you would do by hand.

The code itself has more details, but a simple lookup table that's very similar to the asciitable provides the right number of "presses" to get to each letter. There are settings in the code that define how long the button press duration should be, and how long it should wait in between presses. It takes the LED display longer to save a letter than to cycle through the available letters, since it's storing off data to flash.

Step 4: Add USB Host Shield to Receive Txt Messages

Picture of Add USB Host Shield to Receive Txt Messages

Once the aduino-to-LED Display part is working, we attach a USB Host to to enable sending sms text messages to the display from an Android phone.

Solder on the LED wires to the host shield as shown since the shield covers up the arduino female headers where the wires used to go.

Step 5: Load SMS Pass-Through Program on Anroid

Picture of Load SMS Pass-Through Program on Anroid

You'll need eclipse and the android code linked at the top. Open the project by choosing File-->Import.

Make sure your android phone is configured for development. You need to go into settings-->Applications and make sure the "Unknown sources" and Development-> "USB debugging" options are checked.


Then you should simply be able to attach your phone and hit run. Txt messages should should up on the display!

Getting Eclipse up and running can be a little tricky, so

Comments

jrwil (author)2014-09-25

I chose this as my first Arduino project and hope my experience will guide others. My use for it is as a social experiment; I put the device in a car window with a message inviting strangers to text the display.

• I used the same Arduino in the example, the Duemilanove.

• I used the same LED display and would recommend only that display — glowproducts.com is the only outlet I found that sells this particular belt buckle. Shipping to the U.S. takes about a week. Alternative displays did not work. The price has increased to $19, but including shipping, it’s $30.

Alternative displays place the batteries too close to the switches and do not include the plastic back, which is preferable. I did not have to remove any plastic from the back for the wires to emerge. The buckle I received was missing the component marked U1 visible in the example photo below the page up button, but it did not seem to affect its operation.

Weak batteries powering the display will cause the Arduino to write gibberish.

• I used a different USB shield from ITead Studio. The Sparkfun shield has notorious power issues and is not best for a novice. The shield I used allowed for out-of-the-box connection to the Arduino, and mysteriously corrected an “OSCOKIRQ failed to assert” error showing in the serial monitor that is sometimes attributed to voltage problems. The shield is $30 including shipping.

http://www.robotshop.com/en/usb-host-shield-arduin...

• The phone I used is an LG Optimus Dynamic CDMA running Gingerbread and offered by Tracfone. This phone is only $20. Tracfone has roaming restrictions on their Android smartphones, so if you use this device, make sure they offer CDMA service in your zip code.

http://www.amazon.com/Optimus-Dynamic-Android-Prep...

The issue with this being a portable project is that the phone will try to charge itself using the USB shield, which obviously drains the battery. I tried to find ways to disable USB charging on the phone but was unsuccessful. Apparently has been done on rooted devices before, but rooting methods for the Optimus Dynamic no longer work, and I suspect that rooting the device might interfere with Microbridge anyway.

• I used the version of Microbridge linked in this thread:

https://code.google.com/p/microbridge/issues/detai...

Cheers!

zombiemom42 (author)2013-09-15

Would it work this the arduino mega adk?

compsfreak17 (author)2012-04-05

Never mind on my last question, but a new qyestion. Does the baud rate have to be 57600, because the module im looking at is set at 9600 bps.

compsfreak17 (author)2012-04-05

What lines would i have to take out so this runs only with serial communication? I plan on getting a cheap serial bluetooth module and using that with my cell phone instead of sms.

kbhasi (author)2011-11-11

Can we use the gsm shield instead of the android phone?
https://www.instructables.com/id/Arduino-GSM-shield/

mikeasaurus (author)2011-11-05

I like this idea!

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