Suggestions for RFID Door Opener


I'm new to the forums and Arduinos in general, but for one of my first projects I have been wanting to make an RFID door opener. This is for my dorm room, so I can't modify the door or lock mechanism, so I wanted to have a servo attached to the deadbolt. My first question is whether I can run a bidirectional servo straight from the Arduino pins, or through a transistor or relay if the motor needs a higher current power source. I am not sure if I would need to get an H-bridge or a motor shield kit to accomplish this. (sorry, I'm sure this has been answered somewhere already; if so, just a link would be fine for me)

My second question is in regard to RFID readers. As of now, my choice is between the Parallax serial rfid reader and the ID20. Ideally, this would be mounted (gently duct taped :)) to the inside of my door, which is 2" solid wood, but with thinner inset panels that are about 3/4". I could definitely fit the reader over one of these panels. Is it feasible to have a keychain-type RFID tag be readable through the door, and which reader would be best suited for this application?

I really appreciate any input, I am excited to get going on this once I have the parts I need.

The RFID readers I mentioned are:


and ID20:

For the servo, you need to measure the force/torque required to move the deadbolt.

Then, you need to find a servo that can provide that amount of torque.

Finally, you need to look at the data sheet for that servo, to find the voltage and amperage needs for that servo.

Then, you can make a decision as to whether or not the servo can be driven directly.

The deadbolt on my front door wouldn't even think of moving when using a servo that can be directly driven by an Arduino.

Can't help you on the RFID readers. The one I have, with the tags I have, has a range of about 1/2" in air. The 2 readers you asked about claim read ranges of 2" to 5", depending on the RFID tag. But, that's with air between the tag and the reader.

A 3/4" chunk of wood is going to cut that range down considerably.

On the other hand, the one I have has a separate antenna that could be mounted outside.

1/ Yes you can drive a servo direct off a Arduino pin.
( But ( 1 ) I would just add a current limiting resistor )
( But ( 2 ) You ** MAY ** have to power the servo off a separate power supply.

I have a ID20 which says 20cm + , using keykobs I`m getting about 6-7 cms Air , so think 1 inch door would be o.k

p.s just tried a 1 inch think book so ???

I was looking at the servo here:

It claims 6.5kg*cm torque at 5V, which I think should be just enough to turn my deadbolt. I looked at the sample sketch that was mentioned there, (, and that led me to believe that I will most likely be able to run the servo as I need to right off the pin.

Thanks, peter247 for the info about the ID20. If anyone else has experiences with the RFID readers, I'd be happy to hear about them.