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Calling All Electronic Buffs- Rfid Project

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Hi guys, looking a bit of help.

I am developing a keyless system for my car, nothing to do with cental locking or anything fancy just for starting it. I plan to do this with a RFID kit, more specifically the MK179. I want to be able to get in, touch a rfid keyfob off a panel, then have a starter button that I push once to turn on the ignition, push (or hold) to start the engine, then push again to stop.

A bit of a faf, I know, but bear with me.

I have the RFID reader, keyfob and wiring it into my car sorted but my problem is with the starter button. I don't know to make it do a different thing everytime I push it. I can't figure out how to make it supply power to the igniton, then supply power to the starter motor then to kill it all again upon each push of the button.

This diagram may explain it better:


Now, I have a good grip on electronics, but analogue eletronics only and I imagine that the above will require a microcontroller or chip. So try and dumb all explations and adive down. :rolleyes:

Any help or advice welcome

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Any use?


You could use this for IGN on and IGN off.

You'd need to locate one wire in that rat's-nest which was only high when the following conditions are met IGN=OFF->ON SWITCH=ON for the starter motor.

Also you could wire it in such a way that the RFID tag when in place activated two relays.

The first would be a latching relay (RFID connected to TRIGGER BUTTON). A feedback wire from the N.O terminal to the input trigger would hold the relay SET until GND was disconnected. This would be IGN (DEVICE).

The second regular relay would simply crank the starter motor when the tag was in place only. A diode would be required to isolate the feedback from the IGN relay permanently cranking the motor relay.

Finally, the push to break switch on the dash (RESET BUTTON) would cut the GND to the IGN latching relay and kill the Ignition and the engine.


TBH most of the push start kits on eBay have this all sorted for you for say £60, they include a nice backlit labelled dash button and a microcontroller in a nice box with some wires ready to install, and they sequence the outputs for IGN before starter etc to make it more like a key turning in the barrel. They also may include features you definitely won't get in a relay-based setup, possibly to include vehicle speed interlock and longer press to stop for safety and accidental operation considerations

Also If your car was made afer about 1998 (and it says it's a 2011 car) then you already have an RFID chip in your key and there is an RFID coil in the ignition barrel. I've seen mods where another RFID antenna was purchased and the wires moved/extended to the centre console coin tray. When the keys are in the coin tray, the car can be started with the pushbutton. The RFID chip was removed from the original car key and placed in a smaller keyring for aesthetics.

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Thanks, that is very useful. I'll be sure to give this a go. I'll let you know how I get on!

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