Category Archives: microcontrollers

Blinky Box

This was a gift for my two year old nephew. Since he is a fan of lights and buttons, I wanted to make something blinky for him to enjoy. The concept was simple: make a clear box with buttons and lights that would change color and pattern based on the buttons that were pressed.

Blinky Box

First, I had to find a clear acrylic box large enough for some LEDs, switches, buttons and a microcontroller. I found this great polycarbonate box from Hammond Manufacturing that seemed to be the right size. Next, I needed to find some buttons that could take a beating. Fortunately, Adafruit sells some translucent arcade buttons in bright colors. The lighting was a no-brainer as I am a huge fan of Adafruit’s addressable LED strips. I also found a glowy on/off switch for the power. Somewhere along the way, I thought it would be a cool idea to add a rotary knob so that he could select different blinking patterns.

The next step was to assemble the pieces and wire everything together. The polycarbonate box was harder to work with than I had hoped. The polycarbonate would discolor if I used the laser cutter, so I found myself drilling all of the holes with a rotary tool. I then added the buttons, knob and on/off switch.

Assembly

Once all of the bits were together, I had to add a microcontroller to control the button states and light transitions. I decided to go with the Teensy 3 as it was what I had on hand (and I had yet to work with one). Also, Teensy 3 allows all digital pins to be interrupted (as opposed to four on the Teensy 2), which would simplify reading the button state. The other great reason for selecting the Teensy is that it already has an Encoder library, which makes reading the knob state simple.

The code was easy. Interrupts on the arcade buttons would change a variable representing the color. The interrupt for the black button would kick off a rainbow display routine. In the main loop, I polled for changes in the rotary encoder state and transitioned the lights accordingly. When I was finished, there were five main light colors (white, red, yellow, green and blue), one rainbow routine and six possible blink patterns (always on, fade on/off, blink on/off, chasing light, random twinkling lights and alternating lights).

IMG_6082

I saved the hardest part for last: power. I wanted something that my nephew couldn’t disturb, so anything outside of the box was out of the question. Regular batteries would require opening the box to change, so I thought something rechargeable would work better. I decided to go with a Lithium Ion battery. Unfortunately, these are generally around 3.7 volts and the LED strips require 5 volts. This meant that I needed to find a way to recharge the battery from the outside and find a way to step up the voltage. Fortunately, SparkFun sells a power cell board that does both. Yay!

Power Supply

I added a power jack to the box and used an old 5 volt AC adapter to supply the charging power. I then connected the power cell board and the battery using this handy tutorial. Fortunately, the charging of the battery seemed to work! Unfortunately, the power cell board only provides 600 milliamps at 5 volts, which is not enough power to run a full meter of the LED strip. Sadly, I had to cut the strip in half. It was still impressive even with just one loop of lights! To make the battery last even longer, I also implemented some of the suggestions for conserving power with the Teensy.

The best part about this toy is that it is fully programmable. As he gets older, I can program new features or games into it. Perhaps one day, I can even teach him to program it himself! 🙂

Here is a short video of the assembled box

Microcontrollers!

IMG_6193

Looking through some of my electronics stuff, I realized that I ten different kinds of microcontrollers! That’s not bad at all, considering that I only discovered my love of them last summer. There are five flavors of Arduino: Uno, Uno Ethernet, MEGA, MEGA ADK and Due. There are three flavors of Teensy: Teensy 2.0, Teensy++ 2.0 and Teensy 3.0. There are also two wearables: Lilypad Arduino and Adafruit Flora. So many microcontrollers, so little time!

Motion-Sensitive Paper Lantern

Back in February, I made a motion-sensitive lantern for the Lunar New Year. The idea was simple: have a lantern that appeared to be mostly plain but would reveal a design when a person moved closer to it.

Lantern from far away

The easiest form to use was a round paper lantern. I started with a 14″ white paper lantern and some markers. I then attempted to draw some snakes on it, as 2013 is the year of the snake. As I am not an artist, let’s pretend that these squiggles look like snakes.

Lantern up close

The next part was to add some lighting. The lighting needed to change color. I decided to go with LED strips from Adafruit, as I could wrap them in the center of the lantern and have fairly uniform lighting. I had some left over pieces from a previous project and this seemed like the perfect occasion to use them.

Next, the lighting needed to respond to motion. There were a couple of sensors that would have allowed me to detect motion, but I decided on a passive infrared (PIR) sensor. Interestingly, these sensors work by detecting rapid changes in infrared radiation (including those given off by body heat).

PIR Sensor

The code for this was very straightforward. The PIR sensor sends a high signal on its output pin whenever motion is detected. Therefore, it’s as simple as polling the output pin with digitalRead() and transitioning the lights based on changes in the output pin state.

Finally, I had to find a lightweight power source. I found an Energizer power pack, which was the perfect power supply for Teensy. It even came with a mini USB adapter, which meant that I could plug it directly into the Teensy without having to solder anything. Here is the final internal assembly of the lamp!

The final assembly

And here is the lamp, fully assembled and running!

Dance Dance Revolution Keyboard

Over the weekend, I turned a Dance Dance Revolution dance pad into a keyboard input device. The pad will be used as part of a larger project at the NYC Resistor 2013 Interactive Show. Here is how I did it.

The pad itself is one of those metal arcade style Dance Dance Revolution pads. The only output was a 15 pin D-Sub connector, much like a VGA cable.

Dance Pad

The dance pad connector

Fortunately for me, a fellow Resistor already went through the arduous task of figuring out the pinout for this particular pad. A little further research based on the pinout revealed that this particular model was a TX-1000. The full pinout can be found here.

The next task was to wire the connector to a microcontroller and try to read input from the board. I decided to go with a Teensy as it already has a library that supports keyboard output. In order to have the Teensy be recognized as a HID by a computer, you have to change the USB type. This can be done by changing Tools -> USB Type to “Keyboard + Mouse + Joystick”.

Now I needed to write some code to read the input from the dance pad and convert it to keyboard output. First, I had to define the input pins in the setup function of the Teensy code. This was done with pinMode using pullup resistors.

pinMode(leftPin, INPUT_PULLUP);   // Left arrow

The next step was to read the input from the control pad and send the corresponding keyboard character when a pad was pressed. Fortunately, Teensy offers a Bounce library which makes debouncing switches easy. First you declare a Bounce object on your input pin.

Bounce leftButton = Bounce(leftPin, 400);

Next, poll the pin in the loop() method for state changes. Once a state change is detected, send the corresponding keyboard key.

if (leftButton.update()) {
    if (leftButton.fallingEdge()) {
         Keyboard.set_key1(KEY_LEFT);
    }
}

Once everything was wired up and the Teensy code was running, everything seemed to work… except the right arrow. Unfortunately, this meant that it was time to take the pad apart!

Underneath a panel

The wires

After a bit of investigating and a few false starts, I found that the wires were easily accessible under the up arrow. Thankfully, the wires for each button were a different color so it was easy to determine which wires to test. Testing with a multimeter showed that the right signal wire in the cable was not working. After running a new signal wire for the right pad (and soldering everything else I cut), everything worked as expected! I then used a solderable D-Sub connector and enclosure from RadioShack to make a connector for the pad.

The completed connector

I could then hook the dance pad connector to my homemade connector and then a mini USB to USB cable from the Teensy to my computer. There is nothing more satisfying than navigating your computer by dancing!