Interfacing (DSI, CSI, I2C, etc.) • Magnetic Reed Switches to GPIOs

Hello all,

I have a project where I am trying to connect multiple (14x) reed switches to my Raspberry Pi 3 Model B v1.2 and referencing this post: viewtopic.php?t=194415#p1340999, and have come up with the following schematic.

2-ohm resistors represent a contacted switch & 3k resistors are in series with Raspberry Pi GPIO Pins.
With all switches in contact, the 5v current is 40 mA, each GPIO input pin pulls ~1mA at 2.75v. With all switches open, ~5mA is going to ground.

Does this setup make sense for simple security monitoring & are there any optimizations I could do to the circuit?

Ideally, I would like to add a battery (I have an Ademco Vista 10SE control board hardwired in home with old lead batteries) in the event of a power outage and also a way to integrate Raspberry Pi with the old security system but I'm keeping it simple due to time restraints.

Statistics: Posted by mendokusai — Wed May 06, 2026 2:00 pm

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