Understanding resistors to protect GPIOs

[LarryD]

• The technique in the link below, shows how to do similar when we are using an UNO Rev 3 (5v controller).

• In the below post we use 240Ω resistors to protect the GPIOS.

• For a 3V3 Arduino the resistors will be larger.

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Lets Protect Our Arduino From Us This has been covered a few times. The following will show how we can save our Arduino from ourselves. There are quite a few new Arduino users that damage their Arduinos by accidentally shorting output GPIO pins. Suggest new users (and some of us oldsters too) use the following technique to prevent output GPIOs Arduino pin damage. [A] [B] [C] [D] [E] [F] [G] [H] [I] Edit [LED Display X10 with Prewired Jumpers A] [LED Display X1…

• When we set a pin to input, the new series 240R has no significant effect on a digitalRead as the input resistance is 100meg.

• When we set the pin to output, the 240R can be connected to a LED, base of a BJT or the gate of a MOSFET; 240R has a negligible effect on a output pin.