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Digital time zone clock/temprature sensor project

Discussion in 'Sensors and Actuators' started by Iain, Aug 1, 2012.

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  1. Iain

    Iain

    10
    0
    Jun 23, 2012
    I have realized the complexity, and am now focusing on making a temp circuit.

    It is run by a TMP 36 sensor that is fed into a OP139 and tied with a ADM 660 chip for amplification. I believe it can be fed directly to the ICL 7107 chipset which drives the main display.

    would the op negative side need to be run from the mains voltages?

    and what do people think of this selection of components?

    thanks

    Iain
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,361
    2,756
    Jan 21, 2010
    I would hope that none of this needs to run from mains voltages.
     
  3. Iain

    Iain

    10
    0
    Jun 23, 2012
    fan realy regulation

    Hello all again,

    Sorry not to keep updated,

    so need to re clarify it seems.

    the time zone clock has been put on hold, and thus am focusing on the latter parts,

    I am trying to achieve a temperature controlled fan, with led display. It is obvious now they should have been separate projects.

    The idea is to use a TMP36 analog temperature device.
    There is a four position rotary switch that I need to replace with relays,
    I was going to use a lm339 to turn the separate relays on,
    however I am having trouble working out the logic circuit to turn them on and off, I was thinking a voltage detector may work, and would like some assistance if possible,

    Settings: RPM logic sensitivity
    1: off 0
    2: 50% 550 <170mv
    3: 82% 900 171-220mv
    4: 100% 1100 221-280mv +/- 5mv
    240VAC 3 speed fan/dc relay
    FLA 10A? (15A 120VAC)
    Motor size is 75x18.. How can I find a similar sized motors, I am not sure what this means..

    thanks

    Iain
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,361
    2,756
    Jan 21, 2010
    An LM339 can't switch a relay on its own, but with an extra transistor or 2, no problems.

    I presume the TMP36 outputs an analog voltage, if so, you can simply connect several LM339s up to it as comparators and set the switch point of each to appropriate levels.

    The next trick is ensuring that only one speed is selected.

    You need to ensure a relay is only powered if the output of it's corresponding comparator is high, but the one above it (in temperature) is not.

    This *could be done with more LM339s, but you could probably do it in a simpler way.

    In addition to all of this you would need to have hysteresis in your comparators so that the motor isn't constantly switched between 2 speeds if the temperature hovers in the transition region. The hysteresis must be smaller than the range between speeds.

    Finally, you need to check what happens to the motor if you accidentally apply power to two windings. A relay failure could cause this. If bad things happen, you need to figure a way to ensure it won't happen.
     
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