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CMOS or some kind of processor?

Discussion in 'Electrical Engineering' started by [email protected], Apr 9, 2006.

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  1. Guest

    I am off on another project, making a smart controller for a solar
    I am going to be looking at temperatures in a couple places and a real
    time clock, flipping some valves and starting motors.
    Assuming the "outs" are all opto isolated basically LED drivers and
    the "ins" are all digital when I get them, should I use a small
    processor to keep the time and run the logic or should I just go with
    a 4xxx CMOS solution and some RTC chip?
    What is a good RTC chip for CMOS integration?
  2. Guest

    I am not worried about squeezing every available BTU out of the system
    since we have plenty (Florida). I was going to switch on ambient air
    temp and tested by looking at the delta between water in and water out
    with a comparator. Time that to the solar day as a master gate. If I
    determine it was not worth turning on the solars by around noon or 1PM
    I would just open the valves for maximum flow turn on the pump and
    churn the pool water long enough for sanitation. If after that I
    decide solar might give me something I would move that valve.
    I have a year or so running the system manually so I have a pretty
    good idiea when it is worth running. Basically the air temp needs to
    be somewhat higher than the water and the sun has to be shining.
  3. Guest

    Comparator will give me a 1 and an 0
    I don't really care what the absolute temp is, only if the water is
    warmer or cooler than the air and if the water coming back from the
    solars is hotter than it was going up.

    BTW I have a scheme using a garden variety HVAC thermostat (ambient
    air) and a couple regular plug in the wall timers that will give me a
    huge chunk of what I need. (the result of my testing experience)
    I already use a comparator based on an automotive water temp sending
    unit, a pot and a whetstone bridge feeding a 741 in my spa thermostat.
    If that was two sensors I would have my in and out comparator.
    I was just trying for a more elegant solution.
  4. He could use another opto-isolator fed into an interrupt to count
    the mains frequency. That would get around the crystal (which
    isn't going to be accurate enough anyway).

    I'd worry about the safety of this contraption around water though.
  5. Guest

    The only part of the "contraption" around water is listed Jandy 2440
    valve actuators. Everything else is safely in a utility building, GFCI
    protected and optoisolated.
  6. That's a good plan but like all good plans... Not to mention the
    liability aspects of anything home-grown.
  7. Guest

    It is clear you have never looked at the shit the "professionals"
    Most name brand spas are not listed by a NRTL (none of the secondary
    or tertiary ones are) and all pool electrical systems are field
    I can handle the 680 issues.
    I am really looking for the simplest solution, using as much off the
    shelf hardware as possible and I am not happy with the Aqualink or
    similar product.
  8. Keith

    Keith Guest

    Your "professionals" may sell shit, but it's their liability. If there is
    any suit, *I* would not want to explain to a jury how my design was better
    than that of a "professional's", even though I am a "professional".
    Can you handle an ambulance-chaser and a jury that's just seen autopsy
    photos of a crispy neighbor kid?
    The simpest solution is likely to be an X10 system running bog-standard
    hardware. ...everything with a UL sticker for the intended use. At least
    you might be able to point the leaches to a larger money vein. I wouldn't
    attempt to control a spa or pool with unlisted hardware.
  9. Guest

    The 120v AC controls were permitted and inspected, I am olny dealing
    with the low voltage side. Let it go.

    I need a solution for LED drivers, that is all this will control.
  10. Keith

    Keith Guest

    I can let it go, but you can't. This is a *BAD* idea.
    If you have to ask how to drive LEDs this project is *WAY* beyond your
    capabilities! Let it go!
  11. ehsjr

    ehsjr Guest

    What precisely is *BAD* about his idea? He has an existing
    system that is already installed and inspected. He has been
    running it manually - now he wants to use the low voltage
    control capability that is already built in to the UL listed
    stuff. So how is this *BAD* ?

    If you think that's what he's asking, his question is *WAY*
    beyond your ability to comprehend. It seems like you didn't
    see it. Perhaps if you go back to the original post and
    follow the thread you'll get a better idea.

  12. Keith

    Keith Guest

    He doesn't even know how to drive an LED, yet he *thinks* he knows how to
    properly isolate the mains from water. ...not to mention the long line of
    lawyers that *will* line up if this home-brewed kludge fries somone. No,
    even though I know how to do this, I'd not go there. ...too many
    opportunities to make a bad day for me and the opposite for an
    ambulance-chaser. Yes, this is a *BAD* idea. Do it with X10 stuff.
  13. Ben Miller

    Ben Miller Guest

    You do know that the op is an electrical inspector, right?

    .. ...not to mention the long line of
    I would be less trusting of X10 signals than hard wiring if I was concerned
    about reliability. Nothing that he described will be able to cause a major
    malfunction or override any UL Listed safety controls. His main heaters
    have over-temp safeties, and the pump is protected. If he runs his circuit
    from a UL class 2 transformer, there is no electrical hazard. He is just
    trying to capture a few BTU from the sun. At worst, a valve will be in the
    wrong position and he will not get the solar heat.

    Ben Miller
  14. Guest

    On Tue, 11 Apr 2006 22:46:43 -0500, "Ben Miller"

    Thanks for your support.
    Thank you everyone who responded.
    I did some plumbing changes today and got the whole problem down to
    switching one valve actuator and turning on one pump.
    When I actually drew out the truth table and looked at the states I
    really can do this with 2 timers, a relay and some switches. All of
    that will be 6vdc driving those LEDs (The pump is controlled by an SSR
    as part of the original installation, safely far from the pool)
    The master timer will still be a regular off the shelf unit, supplying
    the 6vdc and 24vac power supply for around a 12 hour solar day. I will
    watch ambient temp with a regular HVAC mercury thermostat and if I see
    80F or so I will turn on the pump and switch the valve to solar (a
    relay switching 24v to the valve and 6v to the SSR) Six hours later,
    if the solar never came on I will just turn on the pump with the valve
    wide open for max flow (the default state when the relay is not
    picked) to churn the water for sanitation until the master times out.
    That timer might be a 4060 ripple counter and a 2n2222 to pick the
    SSR. I may pick off a smaller slice of the 4060 to limit the time the
    valve is driven in case a limit switch in the valve fails.
    I have a comparator looking at the water temp in and water temp out of
    the solars but I am not sure I even need it. In the time I have been
    using this I have figured out if the ambient isn't 78-80 by 1PM I am
    wasting my time trying to solar heat the pool.

    The other valve actuated features (swapping spit with the spa etc)
    don't have to be part of this problem. The solars are useless for spa
    heating beyond what the pool gets.
    Running the fountain (another valve) is pretty much mutually exclusive
    of heat and will go off a normally closed point of the "heat" relay.

    I am really trying to interlock these valves so I won't be able to get
    an undesirable state.

    I did look into making this more capable/complicated and the little
    processor idea but I will save that for something biigger. Maybe my
    weather/tide station. (although Omega has some nice off the shelf
    I am really trying not to saddle my wife or the next owner with
    something that nobody can figure out if I am not here.

    I think pluggable relays and lots of LED indicators along the logic
    path will make something that will be easy to fix if you have a decent
    If it will make Kieth feel better I can point out that none of this
    will be within 40 feet of the pool itself and it will be out of reach
    of the children. I spent extra money on bigger pipe so I didn't have
    to listen to the pump and still get good water flow..
  15. Guest

    That's what I am afraid of ;-)
    I am a computer junkie as it is. I have 9 PCs running around here
    doing different things. (30 years at IBM may have something to do with
    It was my wife who demanded that I try to keep this simple.
    I am still chewing through the PIC links and thinking of things I
    could do.
  16. ehsjr

    ehsjr Guest

    So you either did not read the original, or you
    have no reading comprehension. I'll eliminate
    the need for you to read the original, by recapping:
    The LED's are optoisolators. The output side will
    control low voltage to his existing setup, which
    is not in question. He's looking to build a controller.
    His question is not "how do I connect the LEDs to
    the controller?" He's asking whether he ought to
    build the controller with 4xxx CMOS or with a
    small processor.

    In fact, he does, probably far better than you.
    But that is irrelevant. It is an existing system.
    He's not connecting the system to the mains - it
    is already connected and inspected and he's been running
    it manually for ~ a year, AIRC. Nothing in what
    he plans to do is associated with isolating from
    the mains. He's working on the low voltage

    ...not to mention the long line of
    Bullshit. There is no kludge. Can't you read?
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