Plush Irradiated Sirloin

• Grab the code: https://makezine.com/11/diyhome_steak/
• Inside, each steak has two 360° super-bright LEDs wired in series. These have frosted lenses that distribute the light evenly in all directions, making them perfect for the inside of plush toys. Because I wanted the steaks to glow dimmer and brighter periodically, I needed some kind of signal to control the brightness of the lights. The Arduino board, my favorite microcontroller solution lately, supports the perfect feature for this: pulse width modulation (PWM). PWM can make LEDs, which are binary, appear dimmer by pulsing them on and off, with varying time ratios, faster than the human eye can see.
• The PWM signal controls the glow, but the Arduino can only output up to 5V, which isn’t high enough to power these super-bright LEDs. I had planned to power the Arduino with a 12V AC adapter, so I designed the circuit to drive the LEDs from the same source. I used 2 TIP 120 transistors to amplify the signal to each half of the meat tray, 4 steaks each. This pumps the circuit’s full 12V through 2 parallel sets of 2 LEDs (2 steaks, 4 LEDs) in series, which works out to 3V per LED.

• For each steak, I made an LED insert with 2 LEDs wired in series and neatly twisted. I spaced the LEDs about 4" apart, so that they would each light up an even half of the steak without being too close to the edges. I made the lead wires really long, and I knew they would be exposed, so I chose red and white wire to match my plush.
• After wiring up the circuit and soldering and testing the LEDs, I finally assembled the steaks. It’s important to make sure all your LEDs are functioning properly first; it’s no fun to debug a sewn-together toy. Since electronics with fabrics could be a fire hazard, I covered the LED leads in epoxy (hot glue works, too) to prevent a potentially dangerous short.
• I positioned each double-LED wire inside a steak, and filled around it with polyester filling. I left the LEDs plugged in, so I could see how the light diffused and adjust them accordingly. When I got them how I wanted, I stitched up the bottom openings by hand, and arranged them together on a tray.

Each half of the tray (4 steaks) glows in alternation with the other. The pattern is subtle and soothing, the way a good nightlight should be. They’re soft, but not very cuddly, as they remain tethered to their circuit board. In the future I could embed smaller circuit boards inside each steak to make a portable, more snuggly version. I’ve also been thinking of making a larger version for throw pillows, or a smaller version with catnip instead of electronics. These steaks have been great conversation starters in the classroom and online, and I hope they inspire people to learn about the politics of our food industry.