RFID Security

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  • Build: Natasha
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J. Sinclair/CONCEPIA LLC J. Sinclair/CONCEPIA LLC There is something very satisfying about making your own cables.

During yesterday's entry I mentioned about removing the keyed ignition switch and replacing it with a toggle switch hidden under the seat. I started to think more about this and although I think it unlikely I will ever sell Natasha, I may take her places that require her to be left securely. A criminal, or rather a smart criminal might case her out, realising there isn't a key slot to bust into, and figure I've done exactly what a lot of builders do; put a hidden switch somewhere. It really wouldn't take long to find it.

For $500 you can buy a system from Digital Dawg that replicates the keyless entry system of higher quality cars but specifically designed for motorcycles. First of all I am not going to spend $500 on security. When all things are said and done, I'm not going to take Natasha anywhere near the other side of the railways tracks. And secondly, there has to be a way to do this using existing off-the-shelf technology. Every day I buzz through three security doors with my little RFID key chain dongle; how can I take that technology and make it work on a motorcycle?

Well, after a lot of research, I have found a solution. It has taken me a couple of days and about six versions to get it right, but I think this will work fantastically. 

Essentially it's as simple as using a RFID detector wired to a latching bistable relay and rewiring the kill switch to act like the key. Swipe the RFID tag next to the headlight (all the components are going to installed inside, with a series of 3mm status LEDs mounted at the base of the headlight), the yellow LED flashes and a buzzer sounds indicating a successful match, then the ignition is ‘live’ shown by the steady illumination of the green LED. Turning off the bike is accomplished by using the kill switch, triggering the NC relay which lights up the red LED; I may consider using a 1hz flashing LED here, as a visual reminder to disarm the ignition, plus it will look like the bike has some sort of active alarm system. To disable the bike completely, the RFID key fob must be swiped next to the headlight again, to open the relay. All LEDs will be off now.

Here is a list of the components needed. Click on the wiring diagram thumbnail to download a full size version.

(Note: I have not tested this idea yet. Use this information completely at your own risk. You have been warned.) 


DEI 611T Mosfet Multiswitch   1 $12.75
RFID Transponder Kit (I bought three for bulk discount)   1 $6.00
3mm 12v Pre-Wired Red/Amber/Green LED - Ultra Bright (12v)   3 $1.52
3mm LED Bezel / Holder - Black (plastic)   3 $0.21
85dB Piezo Buzzer   1 $5.99
Amico 5 Pcs DC 12V Coil SPDT 5 Pin Mini Power Relays PCB Type   1 $1.40
Wire, Heat Shrink Tubing, Solder, Patience.   1 $0.50
Total $28.37

 Current hours on build: 116.0 


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The Four Fifty

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