Circuit for magnetic switch

Other Hardware General Electronics
1

Circuit for magnetic switch

I think I know just enough about electronics to start blowing stuff up, so I wanted to get some help and hopefully friendly advice. My plan is to have an Arduino talk via a network to an RN-XV wifi module. What I want to know is that if I hook a magnetic switch to one of the RN-XV's GPIO pins, do I need to add anything to the circuit to protect the module? In my simple tests I have 3.3v regulated power go through switch to a GPIO pin. No resistor. I have seen circuits with sensors like this both with and without, so I'm not sure how to know if you need one and if so, what value it should be. My assumption is the resistor is usually there if you need to control the value of an IO pin at powerup, before the software kicks in.

The GPIO pins on the RN-XV are a little different than the Arduino, as an example here is what the data sheet says for GPIO 1 - 8mA drive, 3.3V tolerant.

The Data sheet for the RN-XV is here: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Wireless/WiFi/WiFly-RN-XV-DS.pdf

The magnetic switch I plan on using is a simple home alarm system type of switch (SM-204Q) http://www.seco-larm.com/Magnet2.htm

I appreciate any suggestions or comment.

Thanks,
Chad

2

Might you mean a pull-down resistor when you mention "no resistor"?? I would expect a pull-down resistor is needed if the switch connects to the positive supply (unless the RN-XV GPIOs have programmable pull-downs?)