You may remember I launched three RasPiO® boards a couple of weeks ago. One of them, the RasPiO® Breakout Pro, offers protection for the GPIO ports on the Raspberry Pi.
I thought it might be interesting to explain how the port protection works, so I’ve made a little video about it…
Current Limiting Resistor
One of the ways you can potentially damage (or kill) your GPIO ports is to try and draw too much current from them. You’re not supposed to draw more than 16mA from any one port (and 60mA from ALL the GPIO ports) at any given time.
Most ‘superbright’ LEDs can easily demand 30mA. Usually you are encouraged to put a resistor in series with an LED to limit the current. In reality, a lot of people don’t do this (and many get away with it). But with RasPiO® Breakout Pro, each GPIO port has a 330 Ohm resistor which limits the current output of each port to 10mA. It means you don’t need to bother with additional resistors for your LEDs.
Over/Under Voltage Protection
The other thing RasPiO® Breakout Pro protects the ports from is if you connect the wrong voltage to one of the ports. The Raspberry Pi runs 3.3V (3V3) logic. If you accidentally connected a GPIO port to 5V or 12V, or a negative voltage, you would kill that GPIO port very quickly. I have killed the SPI ports on one of my early Pis when I had a screwdriver accident. 12V into 3.3V doesn’t go well :(
So RasPiO® Breakout Pro has a 3V3 Zener diode on each port to protect it from “the wrong voltage”. If you connect a voltage that’s too high, it will “chop off” anything above 3.3 Volts. (It also protects down to -0.7V).
And thus your Raspberry Pi’s GPIO ports are protected.
Here’s a link to the RasPiO® Breakout Pro page RasPiO® (you can buy one there also).