Motion sensor with transformer query

RealX1

Try to bare with me because I'm a new at this. I'm using a motion sensor to control lights but the lights are 12v and the sensor outputs 120v. What I'm thinking is that the transformer(120v to 12v) will power the lights but 'only' if the motion sensor closes the transformers 12v output loop. Is there a powered switch for this by which the switch will only change(completing the 12v light loop) if sensor goes off and activates the switch?
To clarify, this transformer gets power(from an outlet) and has two leads coming out to power garden lights(12v, 300w max) but the sensor has to decide whether the lights get their power from the transformer. Can this type of transformer work for this? Am I on the right track?

Sorry this was wordy but I'm a beginner. Some other info is that the sensor supplies 300w max just like transformer but the volts are too high for the lights. If I connect a simple 120v/12v transformer to the sensor output will the lights still get the 300w and I can forget about the transformer I have altogether?
Thank you for your time.

Mobetta

Low voltage lighting transformers are available with motion sensing capabilities. Let's say you don't have
that type of system and are trying to use a conventional motion sensor to do the job.
In this situation your best bet would be to interrupt the existing circuit that is feeding the
outlet for your low voltage lights with a contactor. A general duty 20 amp contactor with a 120 volt coil
will do the job. Mount it in a 664 pull box. Run the switch leg/redwire from the sensor to power the normally open contactor coil. When
it receives voltage it will close the circuit to your existing lighting outlet and power your low voltage transformer. If you
try to feed the outlet directly from the sensor it will most likely not be able to handle the potential loads
imposed on it and it will be destroyed.

RealX1

Thank you for your quick response! As I have never attempted this before you're saying I can just get a transformer(120v/12v) with motion sensing capabilities and that will solve the whole problem?? It just needs a similar motion range as a conventional sensor.

Mobetta

I'm not sure exactly what is on the market but just for fun I Googled motion sensor low voltage lighting transformers and found a site that said they were available. Hopefully they are designed so that you can run the sensor from the transformer to a remote location of your choosing.

RealX1

I looked into these transformers as well but I can't find one that supplies the 300w I need. Each light is 12v/50w and total of 250w across all lights. You're saying if I connect the sensor output(120v/300w max) directly to a 120v/12v transformer connected to the lights it won't work?