I’m working on doing RFID car door unlock. Eventually RFID will start the car, but door unlock is my first goal. This project is going to be clean, no wires hanging from windows or any of that. So the RFID reader will be inside the driver’s door behind the door handle. The RFID tag will be embedded in my hand. As I reach for the handle, it should unlock.
I ordered a olimex mod rfid and the range is awful. It claims 15 cm, but gets no more than 4. Through 2mm of plastic, it doesn’t even function.
I need an RFID reader that can go through 2mm of plastic, 2 inches of air, and 1mm of skin. I would like the reader to cost less than $100… but if necessary, I will spend more.
That is going to be extremely difficult to do in that application due to the amount of metal in the car door and handle. Your best bet would be to make a ferrite bar antenna for the RFID reader. It is still going to be tough because all the metal structure is going to clamp the field. You will also be draining your car battery because the RFID reader circuit will be on continuously driving an active antenna. In my opinion, this project is not feasible, especially with the budget you propose.
phishguy:
That is going to be extremely difficult to do in that application due to the amount of metal in the car door and handle. Your best bet would be to make a ferrite bar antenna for the RFID reader. It is still going to be tough because all the metal structure is going to clamp the field. You will also be draining your car battery because the RFID reader circuit will be on continuously driving an active antenna. In my opinion, this project is not feasible, especially with the budget you propose.
I’m talking $100 for just the reader/antenna combination. Everything else I need is already in place. My car is fairly heavily customized. The RFID’s power will be a drop in the ocean compared to the other draws while the car is off.
The handle of the door is actually made out of a heavy plastic. So if it is directly behind the handle, it will have less metal to deal with.
In actuality, if the antenna is small and can handle getting a little wet, all the electronics can go in the door and the antenna itself can be behind the part of the handle you pull on.
If going outside the door, I have 2 inch length to play with and about half centimeter pole diameter. What kind of range would I be able to get out of a ferrite bar antenna and the Olimex RFID reader? Is there any way I can get more power to the antenna… like amplification?
Forgive me… I’m a noob when it comes to antennas and the like.
To get that kind of range with an implantable transponder, you would need to drive more antenna current than the cheaper RFID readers provide. You can not simply add an amplifier to boost the current because you also need to pick up the signal from the same antenna drive. This requires increased filtering and amplification of the returned signal. Microchip used to sell RFID transponders and had application notes on how to design a RFID reader using a PIC, drive transistors, and a detector / filter circuit. The application notes also went into antenn design if I remember right. You might want to search on their web-site to see if you can find it.