View Full Version : Teensy 3 Newbie questions

11-10-2012, 12:33 AM
I received my Teensy 3 today with the Teensyduino Tutorial kit. Surprisingly I got a breadboard too with my order so that was nice.

I used to have a Teensy 2++ a year or so back but lost all my micro-controller stuff in a move to Michigan this year.

I have never worked with 3v inputs and wondering if the Tutorial kit will still work with the Teensy 3.

Is there a place to start with this? I installed the Beta 6 Windows software for Teensy 3 and see the blinking LED on it so that's good (after I set the Arduino IDE for Teensy 3). Wow it has an overclock of 96 MHz too!

I'm concerned about connecting a LED to the Digital Output. Can someone direct me on this as it is 3.x vdc and not 5 (using a resistor and LED for that). Is the resistor needed then?

Just a little help knowing what to do next and it safe for this Teensy 3.

I learned a little C and rusty on Arduino code but I'll get it. I just want to run through some tutorials again that are safe for the Teensy 3.


Tim Gilmore

11-10-2012, 01:02 AM
Teensy 3 runs at 3.3 V from its onboard regulator. The forward voltage drop across a typical LED depends on the color, ranging from 1.7 V (for red color LEDs) to 3.5V or more for blue and white types. You should always use a resistor with the LED to limit current (9 mA maximum direct from a Teensy 3 pin) but the value of the resistor will vary depending on the LED type.

As a concrete example, say you have a red LED with Vf=1.7 V and you want to run 5 mA through it from your Teensy 3 pin. You want (3.3 V - 1.7 V) = 1.6 V across the resistor, so by ohm's law V=IR or R = V/I = 1.6 V / 0.005 A = 320 ohms. In practice, you will not get precisely 5 mA, because there is some internal resistance in the chip so it will not produce quite 3.3V under load, maybe you'll get about 4 mA or so, but you should still be able to see the LED.

If you use a LED directly on a port pin without a resistor, you run the risk of damaging the chip due to overcurrent, although I'm not sure exactly what would happen- not recommended in any case.

11-10-2012, 01:51 AM
OK thanks I just wanted to be sure about the 3 v.

However, I now have a more serious issue.

I installed the Teensy 3 beta 6 software for Teensy 3. I have a new Windows 8 laptop I'm using this on. I ran the TeensyDuino software and had problems installing the driver. I found the Windows 8 note and followed it to get the driver to install on Teensyduino. However, once it gets past that point it can't find the Arduino program from the Teensy 3 beta 6 directory. As a test I downloaded the latest Arduino UNO software and Teensyduno WAS able to find the Arduino program and installed ALL the working libraries and I ran the Blinky program and changed the LED command to pin 13 and it worked.

I'm don't think it is seeing the Teensyduino 3 stuff running the Arduino Beta 6 arduno program since I think the Teensyduino software installed everything to the 1.0.1 Arduino UNO software.

I saw the rest of the Windows 8 note about the Testcert.cer and Arduino.inf and arduino.cat files but can not search and find these files. Is there something I'm missing here?


11-10-2012, 02:21 AM
The current version is Teensy3 Beta 7, see http://forum.pjrc.com/threads/99-Teensyduino-1-10-and-Teensy3-quot-beta7-quot

I'm still using Windows XP, and all I can say is it works OK for me. Hopefully Paul can give some guidance.

11-10-2012, 03:05 AM
Thanks JBeale!

That worked. I'm up and running on Teensyduino 1.10 and Arduino Teensy 3 - Beta 7 on Windows 8.

Time to run through the tutorials this weekend.

Thanks again,