Pages: [1]   Go Down
Author Topic: 12v Trigger? Newbie here.  (Read 916 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 29
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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, smiley

Scott

Logged

0
Offline Offline
Full Member
***
Karma: 0
Posts: 235
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Offline Offline
Newbie
*
Karma: 0
Posts: 29
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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?
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 437
Posts: 23662
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Offline Offline
Newbie
*
Karma: 0
Posts: 29
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Offline Offline
Newbie
*
Karma: 0
Posts: 29
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 437
Posts: 23662
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Pages: [1]   Go Up
Jump to: