RPi Alarm Reed Switch Voltage

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Joined May 22, 2015
Hello - I have created a working RPi alarm on my workbench with two reed switches. The issue I have run into now is that when I connect my alarm to the reed switches that are wired to my home doors and windows it does not work. It does work with just one door. I think the problem is that the 5v coming from the RPi is insufficient for the reading of GPIO high/low state.

My circuit is following this example: http://www.projects.privateeyepi.com/home/home-alarm-system-project/installation/alarm-electronics

Can someone please advise how I would add an external power source to my reed switches without harming the RPi GPIO ?