Display Live Txts on Costume at Party w/ Scrolling LED Belt Buckle

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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.

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Step 2: Automate Message Entry on LED Display

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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.
jrwil10 months ago

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.


• 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.


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:



Would it work this the arduino mega adk?
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.
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.
kbhasi3 years ago
Can we use the gsm shield instead of the android phone?
mikeasaurus3 years ago
I like this idea!