And here is the _real_ final conclusion: don't test this kind of stuff with the Phidget USB connected to a USB loader! The Phidget board works differently than when the USB is connected to the USB port of a PC.
Why? Don't have the slightest clue, beats my logic. But as you have understood by now, I'm not a hardware guy, that's originally why I buy Phidgets, so I don't have to think too much about such stuff...
One more thing if someone should happen to read this later looking for help: this motion detector seems to almost have x-ray vision! I was very confused because it kept blinking on/off even if it was "locked away" in a box in the room. Tried all kinds of stuff, with lower voltage and blabla...
Turns out the box (a GoPro bag to be precise) wasn't enough, the sensor could detect my presence right through that! Also reflections from a wall are enough, I think.
So when you think you have your setup ready, access the Raspberry from another pc through wifi and stick the sensor in another room without people. Then you can have fun opening the door and seeing the light turning on or whatever. And see on the other pc that the motion detector doesn't trigger when there's no one there.
After doing that, I can use the 24V I had planned for the TDL, so I don't need to wire 2 different voltages around.
P.S.: The 5V from the phidget board does _not_ work with this TDL version, even though specifications say it should.
