Potato Badge

Introduction

It's the winter break, and what better way is there to procrastinate on studying and university applications than to make your own badge! I was quite amazed by the quality of blinking badges I've seen online and I wanted to make my own that would stand out from the rest. Heck, I did not care if my badge would be the worst of the bunch, as long as it made people turn around and question its existence.

Thus, I am proud to present the first potato-based badge! (As far as I'm aware.)

Demo

How it works

The design for this potato badge is extremely simple. The potato is powered solely by a 3V button cell battery, due to its small form factor. To avoid the complexities involved with using a microcontroller for blinking, I used blinking LEDs, which contain a very tiny integrated circuit called a multivibrator. They allow for a 50% duty cycle between states, effectively switching them between on and off states. As a bonus, this allows them to switch on and off out of sync with each other, which looks pretty cool.

The LEDs are then wired in parallel to each other, then in series to a basic push button switch and power source. All together, this created a blinking circuit that could be toggled at the push of a button.

Preparing the potato

To get more headroom for the components, use a relatively large and round potato (diameter > 2.5 in). Cut the potato along its middle point, and hollow out one half with a spoon. Leave around 1/4in so the walls of the potato are relatively sturdy. On the other half of the potato, cut out 1/2 inch of potato for extra room for the components. You can carve out more if needed.

Building the internals

Get a suitable number and variety of blinking LEDs. I used 6, but you can use more if you have a bigger potato. Stick them into the top half of the potato, keeping in mind the cathode and anode placements. I stuck the long end of the LEDs towards the top of the potato so I would remember.

Connect the LEDs together in parallel by soldering their cathodes together, and anodes together. I used stranded wire with the ends stripped by ~1cm to connec the pins. For some more stability when soldering, I used a soldering helping hands to hold the wire at the right position. Then, if I propped the potato at the right angle, I could use one hand to hold the solder and another to use the soldering iron. If using lead-based solder, be sure to be in a well-ventilated area. You will definitely use quite a bit of solder. After a while, you may notice a baked-potato smell. That's what happens when you cook the potato by accidentally touching it with your iron. Try not to eat your creation, no matter how inciting it seems.

Finishing touches

If you're using a standard mini pushbutton, use a needle to poke 4 holes, roughly where the pins should be. I chose to put my button near the center of the potato, where there was more room between the LEDs. Then, strip the ends of two wires, and solder them to opposite pins on the push button. If there's four pins, solder them to two pins that are not connected by the plastic line marking on the bottom of the button. Thread the two wires through two of the holes you poked in the potato, and insert the other pins into the other holes.

Strip the ends of two wires, and connect one end of each to either side of a button cell battery. Secure it with electrical tape. Then, solder the positive wire to one wire connected to the button, and the negative wire to the cathodes. Then connect the anodes to the other wire on the push button. Your wiring should end up like this:

Hot glue your button and LEDs to the potato for extra sturdiness. Finally, close the two halves of the potato together with some electrical tape. It acts as a nice preservative!

Future prospects

Assuming the potato doesn't dry up or go bad by the time you wanted an upgrade, here are some ideas:

• Add more LEDs! Just connect more in parallel to the wires you already have. Though soldering them together will become exponentially more difficult.
• Use LEDs with the same current draw and voltage difference. I used red and blue LEDs, and though they worked well by themselves, the blue LEDs did not have enough power to light up fully when paired with the red ones.
• Upgrade to a lithium-ion battery. If you use the badge enough, you could run out of charge with the standard button cell. However, if you carve out the bottom half of the potato, you could have room for a rechargeable battery and a charger module with a micro-usb port attatched. Here's one: https://bit.ly/2rZRTb6
• IoT connectivity: If you feel that your potato isn't derpy enough, you can add an ESP8266 module. You're limited by the capabilities of a blinking potato, so the most you can do is probably make a website that shows whether the potato is blinking or not.
• Make blinking potato fries? I'm really going out on a limb here. At the end of the day, this simple project fulfills its purpose of being a wacky badge, and any additional upgrades should not be worth your while.