Hi there. I am new to working with arduino related products and am interested in building a selective cat feeder using rfid tags. Sure I could buy a product online but there’s more fun in building it yourself. What I planned to do originally was use a photocell to detect the cats bell on her collar that would trigger a control relay that would open a drawer or door with two additional relays and limiting switches, much like a power window on a car(motor wiring is grounded through one relay.) I discovered this site and found the parts necessary to build this project. I am a mechanic that installs remote car starters so I’m already familiar with bluetooth programming and low voltage circuits. What I decided to use is an arduino or seeeduino v4.2, 125khz rfid module, 125khz tag combo and a few grove relays. Would I need anything else to build this project? Wiring, power supply or other components? Any suggestions would be greatly appreciated.
Hi, @chevette55 Sounds like a cool project 
! The Passive RFID’s Maximum effective distance up to 50mm or 5CM, but I think that too less to detect an RFID tag at the cat bell, but it can be done simply and it works well if the distance is not an issue or tackles the issue by placing the reader somewhere the cat bell get at < 5CM distance.
Since you alredy worked with BT, I suggest to look Bluetooth beacons, you can build the Bluetooth beacon tags and attach the cat bells, and use Bluetooth LE reader to sense the tags, beacons are meant for this kind of proximity applications and last up to a year or more, and it has more radio distance and you can set the sensing distance by measuring the RSSI value!
conclusion:
You can go with an RFID system and it will work, but if you want more sensing distance and more radio performance you can try to use the BLE beacons.
Please try to keep updating your project staus here, excited to see in action. All the best.
Thank you for the suggestions I will look into it.