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eBay PICs

Discussion in 'Oshonsoft' started by Roger Harrold, Jan 22, 2016.

  1. Roger Harrold

    Roger Harrold New Member

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    PIC18F compiler
    I've been working on a hobby project for the last couple of years, on and off, and I could never get the Freqout or Serout commands to work. I suspected compiler bugs and bit-bashed my way around the problems. Last week I went into to my chilly workshop and my project wouldn't run correctly. Not dead, you understand, but not running correctly. I found that gently warming the PIC cured the fault, and I began to suspect that my eBay-bought PIC might be suspect. I replaced it with a new PIC18F2520 bought from a reputable distributor and everything is now fine. The project starts and runs at -15C, Freqout and Serout now run correctly.
    The moral is: buy your components from reputable front-line distributors.
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You can't trust anything on flebay
     
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  3. spec

    spec Well-Known Member Most Helpful Member

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    Roger,
    Did you check to see if the ebay part was a a more limited temperature range: 0 to 70 Deg C for example? Was the circuit properly decoupled as per the manufacture's data sheet? Was the noise and ripple on the supply lines within the manufacture's limits? Under worst-case power consumption, did you measure on the chip pins? If so, what was the actual supply voltage the chip was seeing? Was the clock circuit as per the manufacturer's data sheet?

    ADDITION 2016_01_27
    One of the biggest no nos with electronic equipment is high humidity/damp/condensation. This is especially so for high impedance circuits like CMOS. I thought that my multimeter had faild but when it was put in a warm dry environment it recovered and worked perfectly.

    I know this sounds extreme, but if your work area has no heat and is cold, you could consider making an airing cupboard with good insulation and a small built-in thermostatically controlled heater to keep the temperature around 27 deg C. You can then store all your sensitive equipment in the airing cupboard.
     
    Last edited: Jan 26, 2016
  4. dave

    Dave New Member

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  5. granddad

    granddad Active Member

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    Roger . Was your project on a bread board by any chance ?
     
  6. Roger Harrold

    Roger Harrold New Member

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    The circuit is on a breadboard, but it is fully decoupled. Also, the ebay PIC carried the marking for Industrial temperature range (-40/+70).
    By simply replacing with a Farnell-sourced PIC, everything was good. Some commands would not work on the ebay PIC at any temperature, on the Farnell PIC they work just fine.
    On the basis that if it looks like duck, walks like a duck, and quacks like a duck, its a duck, them it was the PIC at fault.
     
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  7. granddad

    granddad Active Member

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    Roger .. BB's IMHO are ok with wire leads etc I have put DIP IC's in them but really not trusted the connections , not all BB are the same , some junk out there, now I tend to put chip on strip board or breakout board with pin headers then mount on BB.
    I actually made my first ever ! ebay purchase a month ago , came today from Thailand ..... (Fun time ahead ) for a PIC24FJ1024GB610 from Farnell...

    s-l500.jpg
     
  8. Roger Harrold

    Roger Harrold New Member

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    I probably clarify that the circuit is on stripboard, which is my idea of a breadboard insofar as it isn't a proper PCB.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Well it's nothing like a breadboard, and doesn't suffer from the huge limitations and problems that breadboards do.
     
  10. Roger Harrold

    Roger Harrold New Member

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    Which is why I never use them.
    I and my colleagues always referred to a design tried out on stripboard as a breadboard, rather as valve designs used to be tested.
    The application of the term to mean only plug-in boards came later.
     
  11. nsaspook

    nsaspook Well-Known Member

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    Failed final test chip die are unfortunately packaged and sold on the market in Asia.

    My method for small prototype boards is a usually just a section of vector board.
    http://www.alliedelec.com/images/products/datasheets/bm/VECTOR_ELECTRONICS_TECH/70219603.pdf

    Typical small project prototype.
    Gear signal emulator (variable reluctance sensor replaced with Hall sensor) for low speed motor mod for a ion beam mass slit device, 1.9 RPM instead of 1700 RPM to reduce bearing wear. PIC18F1320 controller.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
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  12. NorthGuy

    NorthGuy Well-Known Member

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    I wouldn't order PICs from eBay, but there's nothing wrong with other, less critical stuff. Not to mention, the chips on eBay are overpriced, and the same chip from DigiKey or MicrochipDIRECT may cost less.

    I use lots of breadboards, most bought on eBay - some of better quality than the ones bough in Canada, but some just junk. I use them when I need to check/design a circuit or arrangement. You cannot really do it with stripboard - you must be able to connect/disconnect and rearrange things frequently. Never had any problems with circuits not working on breadboards. May be I'm just lucky.

    I wasn't so lucky with stripboards. They get messy real quick, it's hard to place a probe on it, and I killed quite a few elements when I shorted something because there's too much of exposed metal. I don't use them anymore.

    If I know the circuit which I need, I order custom PCB (they are really cheap today) and solder things in it - it looks neat and works the best.
     
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