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Thread: RFID-Based Auto-lock/unlock System

  1. #21
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    Also i bet if you used a 3.3v arduino a nike+ and put the arduino to sleep until it recieves serial information it would take months if not years to drain the battery.

  2. #22
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    Unfortunately most Arduino boards still uses 8-12mA in sleep mode. Not enough to last months, but certainly enough for any car that is driven at least once a week.
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  3. #23
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    Quote Originally Posted by Herpelcano View Post
    but instead of the nike+ unlocking the car im gonna have a capcitive touch switch either in the door handle or on the window that unlocks the car and sets the ignition to on but only if the Nike+ is in range.
    That's brilliant. The problem I read about with the Nike+ mod was too much range. Touching the door handle is just as simple since it needs to unlock any way and this works around the unlocking when you are within 100 feet issue. I don't want to do capacitive though, because I might have gloves on in the winter. I would rather just put a simple button on the inside of the door handle. I will only do the driver door since 95% of the time it is just me anyway.

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  4. #24
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    i always check out kickstarter and there is a potential cost effective alternative to the active rfid issue.

    this is the project:
    http://www.kickstarter.com/projects/...or-any-embedde

    here is my email to him
    Hello Eric,

    awesome product. I was wondering if you could take a minute to answer a question for me. I want to use this product as an alternative to an active rfid system for an automotive pushbutton start project.

    My question is, how would battery life be for something like this where it may be 'searching' for the network for most of the time.

    Also, is there anyway to reduce the range of this unit. I'd much rather a 4 ft range then a 60 ft range.

    thank you,

    scott
    and here is his response:
    Hi Scott,

    We haven't measured battery life. We have a mode (sleep) that is watch dog timer based and the micro goes into a low power state while the radio goes into a super low power "off" state. The lpc1114 datasheet says that the micro consumes ~4.5uA and the radio datasheet says it consumes 0.02uA... So, we think the power consumption in sleep will be ~5uA max.

    Most CR2032 batteries are around 240 mA hours to 2.0 Volts. So you'll get something less than that. The problem is that to extend the battery life you'll have to have a very long duty cycle and that won't work for something that needs to respond to a human... On the other hand, if the battery unit is the key fob, then it only needs to do a quick scan and TX to the car unit. Right now SimpleMesh doesn't scan but that could be added then you would control the scan duration.... Lot's of variables to work out here...

    You can reduce both TX power and RX sensitivity which also reduce power consumption. Reducing those variables will reduce the range. I think it is best to reduce TX power while maintaing constant RX sensitivity.

    I think it is doable but there are variables to think about for sure!

    Thanks for your interest,

    Eric
    It's worth taking a look at. I think i'm going to bite the bullet on it. wanted to share my find with the community
    Last edited by scott_fx; 09-11-2012 at 12:25 AM.
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  5. #25
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    Thanks for noticing that, Scott. Please let us know what you find out.

  6. #26
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    here's another option that seems more geared for this application:
    http://www.kickstarter.com/projects/...s-a?ref=search

    adjustable range from 3 feet.
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  7. #27
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    For a 125khz RFID option check out this site.

    They are passive tags meaning they don't have a very large range. Maybe a couple inches max. However, you can find very small glass tags that will fit in your key FOB so all you would have to do is keep your keys near the antenna. (cup holder maybe?) I have personally purchased a 125khx tag with an adhesive backing and placed it inside of my cell phone case. It works great.

    The same guy has made this circuit as an ignition cut for his Hayabusa. It could be easily adapted for a car, computer, whatever. The forum thread posed on the site is a very helpful aid in understanding the circuit. The reader above with a flip/flop circuit would be nice as you would only have to wave the tag to turn off and then again to turn off. I'm mounting a tag in my ATV gloves and placing the antenna in the key area of my Polaris Predator.

    Again they are all passive options but any active RFID option will draw quite a bit of juice. Most commercial options will be made to permanently attach to power and will be expensive. You would be best using the above and modifying it or turning to the Arduino.

  8. #28
    Maximum Bitrate tempgp's Avatar
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    did it get anywhere?
    im thinking to do auto door lock with NRF as it seams to arrive to all phones I hate keys so if we use phone to unlock car and home door it would be nice i i probably don't have enough freee time to run it with our projects but i think thats better then RFID and i think i went off topic
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  9. #29
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    A bit of a late post here, but for anyone interested I've been playing around with an SM130 RFID module from Little Bird Electronics.

    http://littlebirdelectronics.com/pro...e-sm130-mifare

    Apparently you only get the SDK if you purchase a development kit from the manufacture, otherwise you have to purchase it separately. Anyway one of the PDF files has Raw COMMUNICATION PROTOCOLS for SM130. It has two communication interfaces; UART and I2C. Commands are kept the same for both protocols but communication frames are different. It comes with a demo/programmer APP which programs the device for various security features and keys if needed and allows you to explore the features and control of the RFID TAGS.

    I knocked up quick auto-control-access application to test the accuracy of the documentation and it all worked as expected. I have other uses for this in mind but had couple of thoughts for car entry:

    First, I only wanted something that works when I'm at the vehicle and this RFID module only has a detect range of an inch or two.

    My thoughts are to incorporate a switch inside the door attached to the door handle, when the handle is moved it powers the RFID transmitter/receiver on for a minute or so. This overcomes power concerns. Although polling every second would drop the power consumption drastically and I'll measure this when I get a chance.

    There are some very small tags along some stick on tags that could me glued to the back of a watch or made into a ring etc..

    Mounting the antennae inside the door handle should allow it to detect a small ring or arm tag.

    The module has 2 Input and 2 output pins under SW control but for standalone control it would be easy to code a tiny micro to handle the data control of the device as only a few commands are needed of basic entry security.

    Anyway when I get the time I'll find the best way to install it and test feasibility for this particular task.
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  10. #30
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    nice idea chip os easy to talk to...
    what about locking the door? same way?
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