Galaxy G2 and Raspberry Pi

[ShaunShep]

Hi GalaxyGuy, I wonder if you can help.

I've created the circuit above, but when I check the output it's only around 1v rather than 3.3v

Instead of wiring the circuit up to the triggers, to track down the problem I've connected it directly to a 12v battery, and the output from the circuit was 3.2v (perfect).

I've checked output on the trigger pins, and they're 13.3v as expected.

I'm struggling to understand why when connected to the battery the output of the circuit is as correct (3.2v), but when connected to the alarm system, it's a really low voltage.

Any ideas?

 

[ShaunShep]

I managed to get this working, but I had to swap out the 3k resistor for a 30k (20k+10k) and then 1k resistor for a 10k. This dropped the voltage down to 2.6v which is enough for the Pi to detect. It was suggested the using the smaller resistors may have put too much strain on the supply hence why I was getting such a low reading.

For the time being I've setup a raspberry pi connected to an intruder trigger, with the polarity set to negative. A java application runs as a daemon on the Pi and listens for a change on the pin. If it's positive it sends out an email to multiple email addresses to let them know an intruder has been detected. Once voltage drops back to zero (when the system in unset), another email is sent out to confirm the intruder has been cleared.

A bit basic, but so far there's something working.