Know How...

Feb 13th 2014

Know How... 80

Geeky Valentines Gift and Cantenna

Make a animated LED necklace for Valentines Day, what hard drive to use in a FreeNAS box, and build a Cantenna.
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Take a look at our transcript here . Make a animated LED necklace for Valentines Day, what hard drive to use in a FreeNAS box, and build a Cantenna.

Animated LED Necklace

So lets take look at the parts and tools needed to make the ultimate geeky valentines gift.

Parts List

- Gemma Microcontroller $7.95 - Mini 8x8 Matrix w/ (Red) Backpack $9.95 - 3.7 500mAh Lithium-Ion Battery $7.95 - LiPo Battery Charger $5.95


- Soldering Iron / Tools - Wire (20 to 26 gauge) - Tools for cutting and stripping wire - Shrink tubing - Hot Glue Gun All these parts can be found on for a total cost around $35. This project involves a little bit of everything and that's what makes it fun, and hopefully won't feel overwhelming. All in all this project took me about 6 hours to complete, so this could be a fun rainy weekend project.

Step 1: Wiring and Soldering

- First take the LED matrix and line up the wires to the holes on the backboard. Carefully solder along down the line, a little tip is to heat up the pad and wire with the solder iron and push your solder where you want it, don't glob it on the iron and try to apply. Take your time, and work methodically. - Now that all the wires are soldered you can take a clipper and cut the excess wire. - Next we'll be soldering the 8x8 Matrix to the Gemma, you'll need 4 separate pieces of wire about 2 inches long. When i strip the ends of the wire i like to twist the metal so it doesn't fray. - Find the wiring diagram here Wiring Diagram - Using the awesome and well made diagram from AdaFruit, carefully solder the wires to the LED board. - I'm doing, Red to +, Black to -, Yellow to D, and Green to C. - Like before use the clippers to cut the excess wire. - Now we need to solder the LED and the Gemma together, like before refer to the Adafruit diagram. - Red to Vout, Black to GND, Yellow to D0~, and Green to A1. - Solder the wires to the pads, a little tip here is to fold the wires around the edge so they won't move around when you start soldering - That completes Step 1! Now we get to play with some software.

Step 2: Source Code

If you're not a programmer don't worry! If you know how to download, unzip a file and copy/paste you'll be fine! I'll being doing this on a Mac, but Adafruit had tutorials listed for Windows and Linux also availible. They're all pretty similar, just differ slightly with file location. - Now we need to set up our Gemma using Arduino IDE, fortunately Adafruit has made a package titled "The Fast Way" that we can download and set up easily. Find it here "The Fast Way" Ardunio IDE Download - Download (for your OS) Arduino IDE v1.05 w/Trinket, Gemma, Flora - Un-zip the package - Before we start pasting in code we need to make sure Arduino IDE has all the info it needs and it set up properly - Download the "TinyWireM" library found here TinyWireM Library Download - Unzip the file and rename the folder by deleting the "-master" - Find your Arduino folder, on Mac the default setting is in /Documents/Arduino/ - Now Drag the "TinyWireM" folder into the "libraries" folder. - Restart Arduino IDE, and you should should under File > Skectchbook or Examples the TinyWireM libraries. - There's only two more things to check, under Tools, Board, make sure to select "Adafruit Gemma 8Mhz". - Under Tools, Programmer, select USBtinyISP - Copy and paste time! Copy the source code CrankyHippo GitHub with animation and source code and paste it into the main window. This code you don't need to make any edits too, but if you do feel like messing with it, this code controls how bright the screen is, and other more in depth options. - Next select the little down arrow on the far right, select to make a New Tab. - Name the new tab "anim.h" as the filename. - This is where we're going to copy our animation code, I've created a couple of my own animations on github, one specifically make for the special nerd in your life on Valentines day, and one of my spirit animal Mr. PacMa... I mean Dot Gobbler. - Now you can click the check box in the upper left corner to make sure there aren't any errors, if you copied the animation code correctly you should be fine. - With your Gemma plugged via USB into your computer, press the small button on the Gemma to get the bootloader initiated. - After uploading to the Gemma you should see your animation boot. Also i'd like anyone to feel free to submit they're own animations, or make adjustments to my code and put it on the Know How Community on G+ I love seeing what our users do with the projects and how much more creative people can be then me. A website i found that made making animations much easier is found at To help visualize your animation, every 0 is off, and 1 is on. The format you need to follower is B at the beginning followed by eight 1's or 0's. Then 9 lines down, with the last line being the length of how long the light is on for. for most of my animations i use 25, which equals .25 of a second. Also don't forget to close your lines with a ",". If you squint you can kinda see Dot Gobbler B01111110, B11111100, B11110000, B11100001, B11100001, B11110000, B11111100, B01111110, 25, Also you have the option to set how many times the animation loops, between 1-255. I want my animation to stay on for awhile so i have my code set to 255 loops.

Step 3: Make a Necklace!

I chose to make a necklace, but if you're feeling creative, there's no reason you couldn't make this into a wristband or something you can pin on your shirt. - Warm up the hot glue gun, because now we need to affix the Gemma to the 8x8 LED board, i looped the excess wire, but if you're more aware you could make the wires shorter. - Carefully glue the back of the LED to the Gemma, i then filled in the edge gaps with hot glue also. Plug in the Gemma and make sure everything works right. - I used some small zip ties to keep the wires orderly. - Next i wanted to locate the battery at the back of the necklace, partially because i used the larger 500mAh battery. If you stick to the Adafruit project and use the smaller battery you could probably make it all one piece without it looking bulky. - I cut the adapter off the end of the battery and soldered new wire to extend the length. - Carefully measure out the wire, because this will be part of the necklace and give yourself enough room to fit it over your head. Also before you connect any wire you should make sure to put on the head shrink tubing. - I also threaded a Blue wire to connect to little mounting holes on the LED board, I wanted to make sure not to put excess stress on the power cables when the neckless will be hanging. - I put heat shrink tubing all along the length of the wires, and down towards the Gemma i pulled it back where i soldered the wire to the 2-pin JST-PH connector. - Then after soldering i pulled the heat shrink back down, and tightened the blue wire used for holding the Gemma / LED in place. - For extra mesure i covered the battery in electrical tape. - Now play with fire! Go along the heat shrink tubing and carefully heat it. This will cover the solder points and hold the wires in place. Plug the battery in and you've got yourself some wearable tech! Now if this is intended as a Valentines day gift, make sure to upload the heart animation.


- The Battery will not charge through the Gemma, it must be charged separately. - Do not get wet, do not feed after midnight.


Adafruit Tutorial Wiring Diagram "The Fast Way" Ardunio IDE Download TinyWireM Library Download CrankyHippo GitHub with animation and source code Tool for making animations Music Credit: Anamanaguchi

Make A Cantenna!


1. Can: You want a can that is at least 5" long and 3-1/2 to 4" wide 2. Pigtail for your gear 3. N-Type Female, Chassis connetor 4. Copper Wire 5. Wireless Adapter with an antenna port


1. Drill 2. Drill Bits (Pilot Bit, Larger Bit) 3. Steel Files (to clean the edges of the hole) 4. A ruler (to measure the can, the wire, and the connector placement) 5. Soldering Iron + Solder 6. Glue Gun 7. Snips


1. Clean the can! 2. Measure the Diameter and Length of Can and plug it into the Cantenna calculator 3. Mark the hole. 3. Drill pilot and bore holes until the hole is large enough to fit the N-Connector 4. File the edges off the hole and the can lid. 5. Cut the copper wire to the length given by the calculator 6. Solder the copper wire into the N-Connector. Cut the copper wire to the length given by the calculator 7. Insert the N-Connector into the Can, with the copper wire on the inside. 8. Hot glue the connector to the outside of the can. Use: 1. Use the pigtail to connect the cantenna to your WiFi adapter. 2. Point and go! The calculator gives us two important pieces of information: 1. Where in the can can we place an antenna to capture 1/4 wavelength of a 2.4Ghz signal. 2. How long must the copper wire be to capture 1/4 wavelength of a 2.4Ghz signal.

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