Small scale Bluetooth module

Discussion in 'Homework Help' started by jednified, Dec 8, 2010.

  1. jednified

    Thread Starter New Member

    Dec 8, 2010
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    Hi guys. Im new here. Is there a bluetooth module which you can configure the range of the the module? For example from a 5 meter range to about 1 ft or less... Currently planning on using BTSerial1 Bluetooth module. Any idea of a less expensive and better bluetooth module?

    Im new to this stuff so please bear with me.
     
  2. sceadwian

    New Member

    Jun 1, 2009
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    It's difficult to control the range especially to the degree you're looking for using the 2.4ghz spectrum, I doubt it's practical to implement.

    Further information might be had by looking into keyless entry units for cars and finding out what frequencies and methods they use for tx and rx. I have a keyless entry/start for my car and it's sensitive to within a bout 5 feet, but the range of sensativity can be 3-15 feet under poor conditions.


    Why are you looking for 1ft range? RF isn't really suitable to this type of application.
     
  3. wayneh

    Expert

    Sep 9, 2010
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    Variable shielding - various screen meshes - might reduce range in a slightly controllable way.

    But, why not just run a wire the whopping 1 foot?
     
  4. jednified

    Thread Starter New Member

    Dec 8, 2010
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    Thank you for the replies sir

    @wayneh & sceadwian

    This is supposed to be a project that would be applied to streets in real life. But as a project, its more practical to make a miniature version of the project.

    If applied to the streets the range would be 5m, but Im planning on making a miniature for displaying purposes and bringing the project to and from school.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    What's forcing you to reduce the range? I mean, who'll know or care if it has "normal" bluetooth range?
     
  6. sceadwian

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    Jun 1, 2009
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    Does it have to use radio signals? On a small scale like that audio signals will work far better, and calculating time of flight for acoustic chirps will help a lot. If the project is about the practical implementations of the systems you're using not specifically about RF technology then replacing it with a hypersonic transducer will make your project dramatically easier.
     
  7. jednified

    Thread Starter New Member

    Dec 8, 2010
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    Err.. maybe I should give the overview of my project... Err.. here it is..

    The traffic sign will broadcast a signal which will be received by the vehicles in range. The signal received will simultaneously activate an algorithm programmed inside the device basing on the offense the vehicle is going to commit and turn on the warning sign on the dashboard of the vehicle indicating that the vehicle will commit a violation if the driver will ignore the warning. If the conditions in the algorithm are met the device inside the vehicle will send the vehicle’s data to the traffic sign.

    And thats it. Instead of actually applying it to the streets, I wanted to make a miniature version to make it more portable. Any ideas on what device to use? Cuz I really dont have any idea what device or medium to use.

    Thank you very much guys.
     
  8. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Bluetooth requires pairing and is generally limited to seven devices. The coils under the road are more reliable and need nothing extra on the car. Why would anyone want a device in their car that gets them tickets?
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    That is my first question. They already have traffic light cameras that detect turning on red, and actually photograph most accidents already. Also there is the radar photo systems on the interstates in some states.

    Is this just a project to show how it is done?
     
  10. wayneh

    Expert

    Sep 9, 2010
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    This still doesn't explain why you need to limit the range. What's the problem if the range is more than the minimum required?

    But I agree that BT is not the technology for this otherwise interesting idea. There's some research going on now about smart cars and roads and improving safety by letting technology do what it is good at (really fast reactions, constant vigilance, not panicking) while still retaining a human driver for what he's good at (pattern recognition, predictive risk assessment). You should learn what sort of RF telemetry they're looking at.
     
  11. jednified

    Thread Starter New Member

    Dec 8, 2010
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    The device is required for all cars upon registration at the local land transportation office.

    @wayneh

    The signal for both signs may overlap each other. For areas where one can stop at this side of the road and one cannot stop at the other side of the road. If the range is too big, it might cover an area where stopping/parking is allowed.

    Thanks for the replies sir.
     
  12. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    In what country? Never heard of it. Sounds more like schoolwork.
     
  13. jednified

    Thread Starter New Member

    Dec 8, 2010
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    Yeah.. it is a schoolwork ^_^
     
  14. wayneh

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    Well, yeah. That's what pairing is all about. And MACs [not Macs ;)] and RFIDs. You can't rely on the simple presence or absence of a signal - you need some way to ID the signal.
     
  15. jednified

    Thread Starter New Member

    Dec 8, 2010
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    For example 2 traffic signs that are 10 meters apart, one would be "No Stopping" and the second would be "No Parking". Each sign's range should be about 5 meter radius. If a car goes into the range of the first sign and stopped, the "No stopping", the the device will "pair up".

    If the range of both traffic signs is greater than 5 meters radius, for example 20 meters radius, both signals will overlap. Thus the car who should only stopped at the "No stopping" sign would acquire the signal of the "No Parking" sign. The car would commit both offenses when it should only commit the "No Stopping" offense.
     
  16. DickCappels

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    Aug 21, 2008
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    Back to the original question for a moment: Most if no all bluetooth modules have a transmitter power control, which can be set over a wide range of output power levels. As noted by Wayneh, a poorly designed antenna is the best way to limit range ;-)
     
  17. jednified

    Thread Starter New Member

    Dec 8, 2010
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    Does that mean there is no such bluetooth module/device in which you can configure its range or has a preconfigured range that is 5 meters only or lesser?

    And can I ask for any other wireless communications where I can get the desired ranged for 5 meters or lesser?
     
  18. sceadwian

    New Member

    Jun 1, 2009
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    Yes, that's what it means.
    Wireless communication is neither assured or range accurate. Something designed for 5 meters CAN under various circumstances be picked up 10-20 meters away, or in various situations be missed even within 1 meter.
     
  19. jednified

    Thread Starter New Member

    Dec 8, 2010
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    thanks sir sceadwian @ sir DickCappels

    Another question. Is there any wireless communications device that will be used in urban streets(buildings all around and etc) that is designed for 5 meters? or lesser?

    I can get away with "various circumstances the signal is picked up more than 5 meters away". Was thinking that there maybe a wireless communications module/device which has, theoretically, 5 meters or lesser range.
     
  20. Georacer

    Moderator

    Nov 25, 2009
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    I suppose IR communications, like the ones cellphones used to have, have that reduced range. I also know that they are quite simple to use too.
    Don't ask me how to do it though...
     
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