The Teensy USB Development Board, now to its fourth revision, the Teensy 3.1, is a tiny 32 bit ARM based microcontroller running at 72MHz. Among its many features, there are 256Kb Flash Memory, 64Kb RAM, 2Kb EEPROM, 21 Analog In pins, 12 PWM pins, 3 UART, 2 I2C and 1 SPI communication pins. Although the microcontroller operates at 3.3V, these pins are 5V tolerant, which make the board easy to use with legacy Arduino shields. Programming this microcontroller is quite simple, too, since the Teensy Loader is seamlessly integrated into the Arduino IDE, the Teensyduino; this, united with its really small form factor and cheap price ($19.99), makes the Teensy a great alternative to Arduino for projects that requires lots of pins and fast calculations in limited space. Check out the Teensy website for more information.
Now, this simple Instructable was born to serve an obvious purpose: to protect the Teensy and make it handier. Being the board so damn small, it is very easy to short circuit pins and harm its circuitry by touching it with bare hands. The Teensy is quite sturdy, though. The one that I used for this project had been soldered / unsoldered so many times that the LED on Pin 13 wasn’t working anymore. With great patience I was able to fix the barely visible trace. To my surprise most of the so abused pins were still working. I decided to employ this board only for testing purposes and give it a glorious enclosure. All its pins are still accessible by removing the lid of the box in case I need them. The only pins accessible from the outside are the Serial2 Pins (9,10), the Ground Pin and the Vin Pin to power the board. I also replaced the Micro-B USB connector with a USB Standard-A connector so that I could just plug the Teensy directly into a computer without any cables in the way. In the enclosure there is a bicolor Red/Green LED connected to the Pins 29 and 28, and the backup battery for the RTC built-in the Teensy itself. I also printed a fancy sticker to give it a professional look.
1. 1 Teensy 3.1 Development Board
2. 1 Texas Instruments TI-83 Graph Link USB Cable
3. Short wires
4. 1 Coin Battery Clip
5. 1 4 Pin 2.54mm Female Header Connector Socket
6. 1 CR2025 3V Lithium Cell Battery
7. 1 32.768 kHz Crystal
8. 1 Bicolor Common Cathode LED 2 270 Ohm Resistors
9. 1 USB Standard-A Connector
10. Soldering Iron and Solder
11. Hot Glue
12. Utility Knife Electrical Tape Small Pliers, Tweezers, Phillips / Flat-Blade Screwdriver
13. Everything I Didn’t Mention (like Double-Sided Tape) :)
Step 1: The Enclosure
For the enclosure I took apart an old Texas Instruments Graph Link USB Cable I wasn't using anymore and with the utility knife cut some holes to accommodate the USB connector and the Header Female Socket on the back. I used this because it fitted perfectly the Teensy and there was room left for something else, plus it was very easy to open. You can of course use anything you want, even 3D print an enclosure yourself and that would make everything nicer.
Step 2: Soldering the USB Type-A Connector
I am always keen on reusing as much as I have at hand, so I (again!) took apart and old, nearly forgotten USB cable. I have dozens at home stored in a box and sacrifice one for this project was a no-brainer. With the utility knife I cut along the sides of the connector, making and incision, and then with a set of pliers I just peeled the plastic off the connector. If you decide to go this way, be careful and work slowly. It takes patience and great attention. These connectors are very well isolated and although the plastic concealing the contacts is sturdy, the contacts are not and break easily. Also, not all the connectors are made alike on the inside: some can be of better quality and have more plastic and metal to tackle with.
I soldered the now freed USB connector on the Teensy Micro-B USB Connector. I wanted to able to unsolder it in case I was going to use the Teensy for other projects, so I lightly soldered it on the top of the other like in the pictures above. Be careful and not let solder get caught inside the connector or it might short circuit the contacts inside.
With the connector secured in place, I soldered the V, DATA-, DATA+, GND Pins on the back side of the Teensy. By watching closely to the picture, you might see that there are spots on the PCB where you can solder these pins. They are clearly marked D+, D-, and you can't miss them. The power pins are just located on both sides of the Teensy Micro USB Connector like shown in the pictures.
I then simply hot glued the connector in place inside the enclosure.
Step 3: Soldering the Bicolor LED, the Crystal and Battery Clip, and the Female Header
I soldered a 270 Ohm resistor in series to the LED anode pins. The Teensy pins support little current (20 mA MAX) and I wanted to make sure not to exceed that value. I then bent the resistors and glued on the floor of the enclosure and I did the same with the Battery Clip and the 4 Pin Female Header. With everything firmly in place, I soldered the wires to the Teensy pins like shown in the picture. Lastly, I soldered the Crystal to the Teensy so that I could use the internal RTC. Remember to put a small piece of electrical tape under the Crystal or it might short circuit pin 3 and pin 4 with its metal enclosure.
- Pin 29: Red LED
- Pin 28: Green LED
- Pin 10: Serial2 TX
- Pin 9: Serial2 RX
- VBat: RTC Battery +
- GND: RTC Battery -
Step 4: Printing a Label & Final Thoughts
As a final step, I printed a small label in order to mark the right pins of the Serial Output Pins Header and attached it to the enclosure with some double-sided tape. That was it.
I hope you liked this short Instructable. If you have any suggestions or inquiriy, please leave a comment in the section below and I will be happy to give you an answer. Have a good time. Cheers.