12v Trigger? Newbie here.

Hello, this is my first experimentation after doing blinkie.

I purchased a RFID reader from ebay a while back, it was $10 and came with 2 rfids and does not require a computer.

I have played wired it up to an led and have played with it getting it to turn on when the right rfid is shown. Basically if I show the right card, the led lights up, when I take the card down, it immediately shuts off, so there is no relay.

Can I hook this into Arduino? It is a 12v signal that comes out of the rfid.

Meaning, can I have this 12v signal, trigger arduino to do something like turn a servo or power an led?

Thank you, :slight_smile:


Yes, you can. Put a potential divider circuit to step down the 12V trigger to 5V or lesser and give it to an arduino... :)

Thats great news! Awesome! Thank you for the response.

Any idea where I would look to figure out which resistors I should use in the potential?

12V to R1 to R2 to ground. Junction R1/R2 to arduino.

Vout = Vin * R2/(R1+R2)

Have R1 + R2 = ~20K So R2=8.2K, R1=12K would get you in a workable range.

Wow, thank you thank you.

I am not that good at math so you just saved me. I will try this this weekend.

Thank you.

Well look at that. I was actually able to pull off part 1 of my project. My RFID keyless entry to my apartment without modifying the door, lock, or striker (I'm not allowed too) is now installed and working beautifully.

I just wanted to say thanks to those who helped me below. I wanted to quit and now that I see progress I am actually ordering another arduino to try more projects.

YouTube video: http://goo.gl/htUYg

Nice! Good camera work too. Clever use of a clamp. Glad to see you're not breaking into someone else's apartment!