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wireless communication

Discussion in 'Microcontrollers' started by MrDEB, Feb 13, 2012.

  1. MrDEB

    MrDEB Active Member

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    I have an idea about using a http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=31 to transmit only a distance of 10feet or less.
    Plan to use a 7555smd and a coin cell with two switches to control the 7555 output frequency.
    The receiver is a PIC that samples the frequency and determines which switch is closed.
    Is this a feasiable plan?
    I need to find out what the 7555 will operate down to voltage wise as well as the transmitter.
    The receiver will have three AA cells so thats not an issue.
     
    Last edited: Feb 13, 2012
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Why not use a PIC at BOTH ends?, then you can use a proper coding scheme (check my tutorials).
     
  3. MrDEB

    MrDEB Active Member

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    Cost and size as well as voltage considerations.
    Yes a pic at both ends would perhaps be the best BUT I am only interested in two tilt switches and knowing which one is closed.
    Using a 7555 I only need the transmitter, two caps, 3 resistors, PLUS it needs (ideally ) run on a coin cell (3v ) unless I can get a larger voltage (two in series)
    My thoughts are sample the in-coming frequency and decide which switch is closed. A counter to count how many HIGHs a pin goes in say 1ms.
     
  4. dave

    Dave New Member

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  5. dougy83

    dougy83 Well-Known Member

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    running a PIC from 3V is no problem.

    You may find that the 555 frequencies you've chosen are too small for common RF receivers; usually they have a form of 'bit-slicer', which is essentially an RC filter of the received signal that sets the threshold (to convert the rx signal to digital). This will cause noise at the RF receiver output and make your frequency detection difficult. I would think the frequencies should be closer to the maximum allowed by the receiver (ie > 1kHz)
     
    Last edited: Feb 13, 2012
  6. Mr RB

    Mr RB Well-Known Member

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    I think it's clever and simple.

    You could maybe improve it a bit by putting the switches on the power line, so the 555 and transmitter are only powered up if a switch is closed.

    I think with a diode and a resistor after one of the switches, you could rig it so either switch powers the device but the two switches still produce different frequencies.
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    A 10F series PIC is considerably smaller than a 7555, is only cheap anyway, it saves on all the other support components used with a 7555 - and cures all your voltage concerns (they work over a pretty wide range, 3V is fine).

    And a 10F doesn't require those two caps or three resistors and WILL run on a coin cell.

    Which is probably 'OK' if there's no other transmitters within range, but such a crude scheme relies on not picking up anything else.
     
  8. MrDEB

    MrDEB Active Member

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    Writing a code for a 10F chip is maybe outta the formula.
    I am kinda new at this pic stuff and only learning Swordfish.
    If I had a better insight on programing language I perhaps would have gone with something else.
    Have a book called PIC IN PRACTICE by D W Smith. Perhaps I can translate a Swordfish code into something a 10F chip can use?
    Am even considering just learning a different language but the learning curve?
    As suggested by dougy83, perhaps change the 7555 frequencies?
    Time to experiment on a bread board.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Right, so cost, size and voltage weren't the concern - just being able to program them :D

    The learning curve for PIC assembler is pretty easy (which is why they are so popular), and suitable code is already in my tutorials - but would need slight changes for 10F series.
     
  10. ghostman11

    ghostman11 Well-Known Member

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    only a guess on my part but like you although i am 18 months into pics i am still very new! however the worst bit i guess we have already done wich is the learning curve from zero, if like nigel sugests you have a crack at ASM youve already done alot of the groundwork i.e like learning that chips need to be configured etc ect etc, the rest is just learning a different structure. if you see what i mean.
    i am learning C i tried swordfish at the start and lasted 2 weeks i just couldnt get into it, but once i am better at C i intend you have a look at other languages just for the experiance of it. ASM would certainly be useful to know. interesting little project you have going i must say. just to throw an idea in the mix does it have to be radio? could you maybe use IR link as the wireless part? i am not fully sure what your project is so i doubt my sugestion is much help :D
     
  11. be80be

    be80be Well-Known Member

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    MrDeb I would write the code for a 10F for you if you want.
     
  12. MrDEB

    MrDEB Active Member

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    Will it need a crystal?
    Need to do some research on this end.
     
  13. MrDEB

    MrDEB Active Member

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    I see Microchip has PICs with XLP for low battery voltage.
     
  14. MrDEB

    MrDEB Active Member

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    found a 12F1822 which is an XLP chip.
    looked over Nigels site and got lost. I shouldn't need another programmer as I have a Junebug which I pulled the on board 1320 out and it seems to work better, no glitches?
    Would be interested in seeing code for detecting two switches and input to the transmitter I am using http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=31
    on the receiver end I just need to decipher the data from the transmitter?
    Will spend more time looking over Nigels site and find my way?
    Now where did I put then bread crumbs to find my way back---lol
     
  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    And it's only $0.73

    Many PIC's have internal oscillators so don't need a crystal, and most will work happily on a 3V supply - you don't need to look for XLP ones.

    The 10F200 would do the job though, it's only six pin (so tiny) and only costs $0.30 - silly money.

    My site contains code for reading switches and feeding an RF module, it uses Manchester coding (as mosy radio systems do).
     
  16. MrDEB

    MrDEB Active Member

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    That 10F200 looks like the ticket
    Only 6 pins and will run on 2v. Wonder how long the one coin cell will stay at 2v? RESEARCH
    I figured manchester code is what I need.
    Now to find about assembly language and reading switches.
    I see that the PIC is ICSP compatable. Assuming I can still use the Junebug?
     
  17. MrDEB

    MrDEB Active Member

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    LOST?
    I downloaded site 1 and acompaning file but opening the fils I get an error DLport.DLL is missing?
    if I open the second download for site 1 I get http://www.webhost4life.com/
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    So why not download from site2? - that's what it's there for.

    It looks like the original source for the driver has disappeared - and as we're on Win7 now it's not surprising.

    However, why are you downloading it anyway? - parallel port programmers are pretty well gone by now, and it won't work on anything newer than XP.
     
  19. sanoopgr8

    sanoopgr8 New Member

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    How to send serial data via wifi to a pc/laptop from a pic16f877a ?

    Sir I am working a Robot which has to transfer its locations information to a control room else where therefore i thought of using wifi as the communication means for the robot to the control room. I would like to know to do it is there any way ? plz help me out in this
     
  20. be80be

    be80be Well-Known Member

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    Sure there a way start your own thread sanoopgr8 or just google xbee
     
  21. sanoopgr8

    sanoopgr8 New Member

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    thankz for responding i ll start a new thread
     

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