rfid central locking.

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katq22

Member - Posts: 6

Joined: September 06, 2005

Location: Australia

Posted: July 09, 2008 at 7:31 PM / IP Logged

I have purchased a cheap RFID kit off eBay that connects a relay (Basically outputs a small 12V current) when the token is put near the receiver, and disconnects after a time once the token is taken away.

How would I be able to set this up so that

1. When the relay is active a pulse is sent on the unlock signal

2. When removed a pulse is sent on the lock signal.

Thanks

Ben

i am an idiot

Platinum - Posts: 13,672

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 09, 2008 at 7:46 PM / IP Logged

That is going to be a piece of cake. I will post you a picture in a couple hours. Unless somebody beats me to it. It is going to take 3 relays, 2 capacitors 2 diodes and 2 resistors. Hint Hint

katq22

Member - Posts: 6

Joined: September 06, 2005

Location: Australia

Posted: July 09, 2008 at 8:44 PM / IP Logged

I am guessing it will use two of this setup linked together somehow. As it will be in a car it will need to be zero draw when in the locked state so as not to flatten the battery.

What program do you used for drawing diagrams? Are there any programs that you can make virtual circuits to test by turning the switch on and off?

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 09, 2008 at 8:46 PM / IP Logged

rfid central locking. -- posted image.

You will have to build 2 of the above. 1 will be for lock and the other for unlock.

There needs to be a third relay wired as follows. If your rfid device outputs a positive voltage, that output wire to terminal 86 of the relay. Ground terminal 85. A Fused 12 volt constant source to terminal 30. 87A goes to the lock momentary relay pictured above. It connects to the wire labeled Switched 12v (+) 87 goes to that same wire on the momentary unlock relay pictured above. If your device provides you a ground output or if you have any other questions, let me know.

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 09, 2008 at 8:53 PM / IP Logged

There will be minimal current draw when in the locked position. It will be fractions of what an energized relay draws.

katq22

Member - Posts: 6

Joined: September 06, 2005

Location: Australia

Posted: July 10, 2008 at 1:13 AM / IP Logged

thanks for your rapid replys. Will this drain the battery if left for say a week or 2???

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 10, 2008 at 5:02 AM / IP Logged

The RFID device will pull way more current than the relay setup pulls. On paper the relays will draw 1.2 Milliamps of current. I will try to remember to build one today and give you an exact number. The 1000 mic cap may change the number a bit, but I do not think so. An energized relay draws 160 milliamps.

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: July 10, 2008 at 5:34 PM / IP Logged

Craig what am I not seeing here? Does the RFID unit supply the line to 85?

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 10, 2008 at 5:42 PM / IP Logged

He said it puts out a small 12 volt when the transmitter is in range. Yes I am assuming that it puts out a positive voltage. In my long post above, there is a third relay. I have the RFID output wire going to 86 and ground to 85. That relay depending on it's state will supply 12 volts to either one of the constant to momentary relays.

katq22

Member - Posts: 6

Joined: September 06, 2005

Location: Australia

Posted: July 10, 2008 at 9:19 PM / IP Logged

So is this basically how it would work? and what sort of a pulse would that deliver? How long? long enough to drive door locks? Can the cap or resistor be changed to change the pulse length, and what Wattage should the resistor be?

Thanks so much for your help.

Ben

P.S. I found a Demo of Smart Draw to make this drawing. Man that program is expensive.

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