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PIC Microcontroller Kit

Discussion in 'Electronic Basics' started by Norm3000, Jul 10, 2005.

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  1. Norm3000

    Norm3000 Guest

    I am looking for a recommendation on a PIC mircrocontroller kit. I want
    to make a timer to control several devices connect to an aquarium
    (pumps, lights etc, all standard 120V devices). So I need a kit with
    like 8 relays and a PIC chip that I can program to schedule the devices
    on daily and weekly cycles. I'd prefer something that has a free or low
    cost C compiler available.

    I think I can figure out the programming aspect of it but I'd like to
    avoid having to design the circuits well as program the chip.

    Any ideas or references would be appreciated.

  2. Tom LeMense

    Tom LeMense Guest

    Hi Norm,

    Does it HAVE to be a PIC? As much as I like working with PIC's (and I do),
    there are other microcontrollers out there that are probably better
    supported by free or low-cost C compilers:

    Freescale's HC08 family is supported by code-size limited CodeWarrior

    Atmel AVR is a GCC target, and (because it's not always straightforward to
    get GCC up and running under Windows) here's a Windows-based port

    If you've got your sights set on the PIC, I've used the SourceBoost C
    compiler with good results

    A Google search on "relay board microcontroller" came up with loads of good
    hits - choose your relays carefully, though.

    have fun!


  3. Parallax sells starter kits using Basic.
    A free C lite compiler can be found:
    A good intro:
    To name just a few. A little Gooogling will reveal much more.

    petrus bitbyter
  4. John Fields

    John Fields Guest

    How do you plan to _not_ design the circuits and still get what you
  5. Byron A Jeff

    Byron A Jeff Guest

    I believe he wants prepackaged hardware that only requires software.

    Personally if that's the case, then maybe getting a prepackaged controller
    is the way to go.

    Maybe somethin like this?:

  6. Norm3000

    Norm3000 Guest

    I believe he wants prepackaged hardware that only requires software

    That was the idea. I can handle C programming and I'm sure I can figure
    out how to toggle the PIC I/O ports off and on at set intervals.
    Problem I have is how to then get the I/O port to drive a relay to
    switch my 120V devices. From what I've seen/read over the past could
    days it doesn't look like it's as simple as connecting the relay to the
    I/O port of the PIC chip. Advice I've gotten so far includes adding a
    transistor and resitor to drive the relay or using an H-Bridge. I'm
    clueless here, if anyone could provide an example schematic of driving
    a relay off of the I/O port that would help tons

    I'm not dead set on PIC. It just looked to me that the chip specs were
    good (16 I/O ports on the chip I was looking at) and there appears to
    be a lot of support/information for PIC processors and compilers on the
  7. Not the cheapest solution, but for low noise, minimum parts count,
    solid state relays (with input tied between positive PIC supply and
    active low output) is hard to beat. No other parts needed.

    That said, there are some very low power relays than might be driven
    directly by a PIC output, but their contact ratings are terrible.

    Probably the next simplest is an N channel mosfet, gate connected
    directly to the PIC active high output, source to PIC negative supply
    rail, with the relay coil tied between something like a 12 volt
    positive supply and the drain. You also need a diode across the coil
    (cathode to positive supply) to suppress the inductive spike at turn
    off. Of course, this only works if the negative side of the relay
    supply is connected to the PIC negative supply. You will also need a
    bypass capacitor connected between the positive supply connection of
    the relay coil and the source of the N channel mosfet to contain
    switching noise. One good way to achieve this is to use a 12 volt
    unregulated supply for the relay, and use a linear regulator to
    produce 5 volts from that to supply the PIC.
    I like them.
  8. PIC is a good choice. MPLAB is relatively easy to use, the assembler
    and linker are quite decent, and it can directly talk to various
    programming tools. I've got both a PICSTART+ (with the modification
    that allows MPLAB to update its code, automatically, for newer
    processors) and an ICE2000, so perhaps I'm a little spoiled though.
    But the chips are pretty hardy and I have to say that the technical
    support staff, while a few of them may be 'dry', are pretty well
    versed folks on the details. And, although I haven't called them in a
    few years, it was only the price of the long distance call to get
    ahold of them. So worth it, I think.

    A lot of folks like the Atmel AVR. I certainly am one of them, though
    my attitude has gone through "mood" swings regarding the company,
    Atmel. My support is through a local FAE and this is mostly a bad
    thing for me, by comparison with Microchip. Funneling questions via a
    local FAE who has to support a large number of various products, none
    of them perfectly, and having to wait a day or two for responses --
    isn't all that great.

    The TI MSP430 is enjoyable for me. But for starting out, I wouldn't
    recommend it.

    All of which gets me back to probably adding my recommendation for
    PICs. I think they would be a good choice, given what you've said.

    However, I think most of the C compilers for it cost something, but
    there may be some code-size-limited versions around for free. You
    should research this part of the question, though. Also, if you are
    looking for preconfigured boards to play around with, I really am of
    little good. I just haven't used any of them.

  9. Have a look at:
    Although the outputs come from an EPROM, you can connect a PIC output the
    same way. If you browse through the Velleman catalogus you will find other
    examples as well, even with a PIC:

    petrus bitbyter
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