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# Thread: Double-check my Teensy 3 current valuies

1. ## Double-check my Teensy 3 current valuies

I teach programming and robotics to high school students with very little electronics background. (Read: if they can destroy a board they will.) They are about to start controlling simple, low-current devices (LEDs, relays, piezo buzzers, etc) with the Teensy 3.0 and I want to make sure I have the correct current data for the pins. (I've done a lot of searching but I get a variety of answers and was hoping that something this basic was listed on the PJRC site but I couldn't find it.)

Am I correct in thinking that the maximum total output current of all I/O pins is 100mA?

Is this the recommended maximum or the absolute-if-you-go-over-this-the-board-will-be-destroyed maximum? The data sheet (http://pjrc.com/teensy/K20P64M50SF0.pdf) seems to indicate that the absolute maximum is 155mA. (Again, I don't care what the value are, I'm trying to prevent 34 students from destroying 34 Teensy 3.0's!)

Am I correct in thinking that each I/O pin can safely handle a recommended maximum current of 9mA?

Am I correct in thinking that the absolute-if-you-go-over-this-the-pin-will-be-destroyed maximum current for each I/O pin is 25mA?

In other words: the Teensy 3.0 can drive an LED with 9mA all day long, but driving it with a current of 20mA risks damaging the pin, and driving a 30mA LED will certainly damage the pin.

Do I understand the physics correctly?

Finally, are the current levels different for analog and digital pins?

2. Have they learned Ohm's law and do battery/LED/switches and so on before tackling embedded microprocessors?
Then the basics of C on a PC before microprocessors?

3. The whole purpose of the Arduino environment is to get people closer to electronics and programming. You have to light the spark before before it turns into burning fire of curiosity ;-)
Arduino provides a hands-on practical approach that allows learning while doing.