RF emitter

Discussion in 'The Projects Forum' started by krgoutham, Jul 13, 2006.

  1. krgoutham

    Thread Starter Member

    Dec 8, 2004
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    Hello
    I am working on a project for energy harvesting and need to drive a piezoelectric sensor with a 1MhZ, 5 cycle sinusoidal signal. Could somebody help me with choosing a proper RF emitter for this application.

    Thanks in advance
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Hi,

    Several questions come to mind from your post. The term "energy harvesting" is interesting, but unclear. Could you explain it?

    Is it correct to say that your piezo sensor is going to be driven by 5 cyles of a 1 MHz signal? If so, how often does this 5 cycle burst repeat? It sounds as if this signal is supposed to be transmitted as a radio signal. At what level? - milliwatts or watts?
     
  3. krgoutham

    Thread Starter Member

    Dec 8, 2004
    22
    0
    The repetition rate is very large (1 min or so). So the repetition is not of a big issue here. I am trying to harvest energy using mechanical vibrations and supply the charge generated to drive the RF emitter which would inturn drive the piezosensor. I do not have calculations about the level right off hand but i would guess (based on literature search) that it is very small (milli watts). Any suggestions about RF emitters (name/brand/company etc).

    THanks
     
  4. Gadget

    Distinguished Member

    Jan 10, 2006
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    RF would probably have little affect on a Piezo, as they respond to mechanical vibration.
    Sounds to me like your after a Transducer that works at 1 Mhz, the sorta thing you might find on a medical Ultrasound machine.
    Also sounds expensive.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    Hi,

    Your project is still hard to understand. As Gadget said, piezo devices tend to run un the ultrasound region, which is a long way from a MHz. As far as picking up and storing rf energy, a tuned tank with a rectifier and capacitor to store charge is probably as good as it is going to get.

    Cheap and available rf emitters tend to be things like rc transmitters, or CB radios. The frequencies are in the 27 MHz region for the CB's, and 54 MHz for the rc controllers. You might check with the amature radio people (there must be an ARRL website) for small rf transmitters - milliwatts shouldn't cause problems with Uncle Charlie (the FCC).

    Some parts of the project - gathering enough energy to retransmit rf sound a bit like the perpetual motion machine - realistically, losses are going to be high enough that this may not be practical.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    The ARRL is not in the habit of encouraging or promoting unlicensed operation of any kind -- period!
     
  7. Gadget

    Distinguished Member

    Jan 10, 2006
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    If the ARRL is anything like the NZART, there will be no one left to object in a few years anyway.... ;)
     
  8. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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  9. Papabravo

    Expert

    Feb 24, 2006
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    We weren't talking about the FCC, but rather the ARRL. Two quite different animals.
     
  10. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    The ARRL isn't a regulatory agency. 47 CFR rules the roost in all telecommunications.
     
  11. krgoutham

    Thread Starter Member

    Dec 8, 2004
    22
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    thanks for all your reply. sorry for not replying back on time as i was travelling. Yea.. i guess a tank circuit is the right thing that makes sense. But i also see people using buck converters. i understand that buck converter by itself is like a tank circuit limited by diodes. THe diodes restrict the flow of the current in the reverse directions. THe output from the sensor (used to energy harvest) is sent into a rectifier. The output of the rectfiers is caught in a capacitor (lets title it as a secondary storage) which is sent into an inductor and another capacitor (primary storage) in series (sort of tank circuit).

    may be i can try building a simple circuit and see what happens.

    thanks
     
  12. mrmeval

    Distinguished Member

    Jun 30, 2006
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    It is a shame for that. I think that ARRL does it to themselves. It's very elitist and radios are expensive. You're scum until you get a license then you're the n00b and treated as such. There main claim to serving the public for their monopoly on certain airwaves is during disasters which is a needed function for now.

     
  13. Papabravo

    Expert

    Feb 24, 2006
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    I think that your comments in regard to the ARRL are inaccurate and uwarranted. In inflation adjusted terms radios are cheaper now than in the 1950's and as for being elitist amateur radio has included everybody who could pass the test from the very beginning. There are no age limits, no gender discrimination, and people from every race, religion, and culture participate.

    The ARRL does not have a monopoly on any airwaves. The FCC and similar organizations in other countries manage the RF spectrum. Each allocation has primary and secondary users. If you're going to shoot your mouth off, you should at least be armed with the facts instead of baseless opinions.

    If you get treated like a 'noob' maybe it's because you opine instead of listening and learning.
     
  14. Gadget

    Distinguished Member

    Jan 10, 2006
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    I just got sick of people talking about Rigs, Weather, The Rose Garden, and which bit of their anatomy recently dropped off (in that order). The Net is Real people... ;)
    (ZL4***)

    Perhaps this should be in another thread..??
     
  15. Papabravo

    Expert

    Feb 24, 2006
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    What does that have to do with the difference between the ARRL and the FCC? I'm just wondering.
     
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