So I want to start a car- Explain to me like i'm five


  • Community Helper

    @MrStein

    For the NFC starter you need:

    Just to elaborate on that a little, what you're doing is intercepting the ignition wire and starter wires from either where the key goes or where the acc/ignition/start button is.
    Where MrStein says permanent relay he means a latching two-state relay, astable is a standard switching relay, buck regulator I gather means a voltage regulator, transistor type will do as long as you have some filtering capacitors on it.

    Normally when you turn the key or press the button it provides power from the battery to the accessory line, next position provides power to the ignition/car system on line, next position cranks the engine by providing power to the starter motor while in the ignition state.

    With the arduino providing triggered outputs to switch these relays you could have one read trigger accessory, or a long read trigger accessory plus ignition. These will want to be via latching relays so that once you trigger them on they stay on until you switch them off again. This is important in a car with electric steering wheel lock, not to mention that it's better not to have the car switch off randomly on the highway if something goes awry.
    The starter motor should always be on a standard type relay that is only actuated while the trigger from the arduino is present. This is so that you don't lock the starter motor in the on position. Driving with the starter engaged is possible but extremely bad for the car.

    The sketch that I put up here somewhere has the different outputs triggered by different inlays, it's the lazy way to do it. A better way would be to use the one inlay to switch states ie brief read for accessory, long read for starting the car, a delay of 5 seconds would be safe and acceptable.

    The way I'm visualising this the relays from the arduino are spliced into the loom and bypass the ignition barrel without actually removing it from the circuit so that you can always fall back to that.

    If I've missed anything, ask away.


  • NFC Ring Team

    Awesome guys, sorry for the slow reply.

    First step now is for me to get a car that I can play around with. Will try and keep this updated with how I get on.




  • Community Helper

    I'm not sure why MrStein says 'neiman', I've not run across it before. He means the ignition loom either way.
    For the car on/ignition mode you're going to have the total current draw from the car across that relay, you'll want to make it capable of handling that. For the engine start really you need to do a similar thing. Inspect your vehicle or the wiring diagram if you have one and make sure it can handle the potential current draw across the relay you use. This will be less if the starter motor is tripped by a standard car relay than it will be in an older car which directly triggers the starter solenoid.



  • As i'm looking up these parts, I thought I'd just ask if there were part numbers/links for the relays. What is the power rating on a typical ignition neiman?



  • Thanks again! Just got a 2002 Aztek. Time to pick up a Haynes manual too now.


  • Community Helper

    Good plan, they're a useful tool those manuals.
    I'd suggest also fusing the relay connection appropriately where it's picking up power. Just in case.



  • Hi. I'm looking to do this myself except I wish to do this in order to unlock my car for now. I wan't to make it to where when I reach for my handle it simply just unlocks the doors. The doors are already electric and they are just a simple switch. I'm thinking the best plan for me is to use adruino to program it. Now as to the videos of the Peugeot posted by Nairod785. What is that board that is actually reading the NFC ring that is taped to the dash? I'm needing that exact board for what I wish to do. I've never gotten to mess with any of this so this will be new but my car knowledge is great along with my programming knowledge so I believe that I can achieve this. Any help would be great.



  • So I just found this literally after asking that question.

    http://www.ebay.com/itm/PN532-NFC-RFID-Reader-Writer-Module-kit-for-Arduino-Uno-R3-Mega-2560-/190992100710?pt=LH_DefaultDomain_0&hash=item2c78042d66

    Is that the board used in the video? Or at least will this work?


  • Community Helper

    Yup, that board is the right one. You'll have to let us know how you go with positioning the reader for unlock.
    You could also conceivably use more than one reader on the same arduino and have the second for starting the car.



  • Yeah I'm trying to figure out where it would work. I feel I could put it directly under the handle but that is mostly metal.. Along with my car. What else would I need besides the board I showed and Arduino to get this project going?


  • Community Helper

    just a power supply appropriate for the arduino and the reader unit, probably 5v, regulated. Plus relays and such to translate what the arduino does into solid electrical connections for the vehicle side.
    If you have electric locking you'll need a relay for that also.
    Rather than the door handle you could place the unlock reader in the empty part of the mirror housing or behind the corner of the window at the dashboard end. Another person I know with an implant from Amal set his car up with a reader behind some plastic flashing that was on the vehicle, outside the metal but well hidden and protected.



  • I really like the Mirror idea. My side mirrors are indeed plastic!


  • Community Helper

    Just make sure you plastic wrap the reader, so it's waterproof!



  • Will do! Are there any websites or links that you would reccomend me going to to read up on programming arduino and NFC along with the resistors? This was I have a decent understanding of what I'm doing.


  • Community Helper

    Relays mate, relays. What you're actually doing is using the arduino to activate a relay which basically closes a switch which isn't electrically part of the arduino circuit. That way the cars 12 volts isn't going through fragile electronic components in your control circuitry.
    MrStein's pictures and diagrams up top explain the physical aspect of the idea quite well, and there should be a thread of mine here where I put a quick and dirty car start sketch that will work with the PN532 reader unit you're getting. It can be adapted so that the outputs trigger anything external basically, as long as you're using the relays to keep everything seperated nicely.
    For further reading on Arduino, the best source is the source: http://arduino.cc/
    They've got plenty of tutorials there, and a forum where you can ask questions of those who've been coding for longer and have some experience.
    There are also a heap of projects out there on the web, google will get you there right quick.



  • Thank you very much for your amazing replies. I mean't to to say relays lol not resistors. I was still waking up before work when I typed that. I realized today that my car does actually have plastic door handles so my original idea might actually work. I'm thinking up having the sensor positioned up from underneath the handle so when I go to grab for it, it will unlock the door.


  • Community Helper

    Yes! That's exactly what I plan to do, though I'm going a step further and removing the door handles. Later. When I don't need to drive for a whole weekend! (Hot rod style door popper kit!)
    I just noticed the code I put up has become a little bit butchered in the forum change, I'll have to see if I can fix that up.
    Also, no problemo!



  • That would be pretty cool! I'm honestly just afraid of doing that just in case it happens to malfunction. That way I can just revert back to my key if all else fails.


  • Community Helper

    I've got andersen type plugs on my car for emergency power injection without popping the bonnet, juuuust in case!
    It's usually required by law to have a secondary method of entry in case of emergency, so I'll have hidden mechanical release as well.