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timer- 120V 0.1 amp '50% on' circuit

Discussion in 'Electronic Basics' started by Mike Westbye, May 9, 2005.

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  1. Mike Westbye

    Mike Westbye Guest

    Guys, I was hoping for help for a rank amateur.

    I've done some minor electonic repairs on power supplies with not much
    knowledge.

    My washing machine's timer motor went belly up and is a discontinued part.
    I've rebuilt the gears a few times, but I doubt this will last.
    I bought a rebuilt motor which runs double speed for another model. Works
    great, but the wash cycle is over in 15 minutes.

    Anybody know of a circuit that will turn on, ie close a relay approx 50% of
    the time? These are Telechron? induction motors so 1/2 wave power is
    useless, methinks
    This thing draws less than 0.1 amp @120V ac and I already have a zoo of low
    voltage DC power supplies.
    If I can pull this off, it will save me $800.00 tax in.

    Thanks in advance for any help offered. Please explain acronyms to this rank
    amateur.
    (people who use acronyms are SOB's).

    Mike in Ontario, Canada -the taxed North (Still Slightly) Strong and (sorta)
    Free.
     
  2. John Fields

    John Fields Guest

     
  3. Chris

    Chris Guest

    Hi, Mike. For benefit of others in the newsgroup, many older washing
    machines control their cycle through a very slow gearmotor with cams to
    control time for "Fill", "Wash", "Drain", "Rinse", and "Spin". The OP
    (Original Poster) has found and installed a gearmotor that will fit,
    but it operates at twice normal RPMs (Revolutions Per Minute). This
    means "Wash" and all the other times go twice as fast, and the clothes
    don't wash for long enough to get clean. By turning his small
    gearmotor on and off with 50% (percent) duty cycle with a period of 30
    to 60 seconds, he can in effect slow down the gearmotor. That will
    stretch out his wash and other cycles so they take their normal times.
    Initially, this concept sounds like it would cause problems, but the
    critical part of the washing machine cycle is fill time/level, and
    that's controlled with float switches anyway.

    You're right that using a diode to half-wave rectify the line voltage
    is worse than useless. Motor speed is controlled by frequency, so you
    wouldn't achieve speed reduction anyway. It will still be 60 Hz
    (Hertz). The big problem is that you're applying DC (Direct Current)
    to an AC (Alternating Current) motor, which will make it very unhappy,
    and probably burn it up within a few seconds.

    You're instinctively headed in the right direction, but you didn't know
    what to look for, Mike. The beastie you want is called a recycling
    time delay relay (TDR). Turn it on, and you can control the on time
    and off time within the limits of the control. They come in solid
    state and plain old relay contact variety.

    Usually I'd recommend a solid state version, because they're a bit
    cheaper. But considering that you're a newbie, you're in luck. One of
    the best 30/60 second general purpose recycling TDRs is made by Potter
    & Brumfield, goes for $185 USD (United States Dollars) retail, and is
    available for only $65 USD from Surplus and Sales of Nebraska.

    http://www.surplussales.com/

    If you've got an octal relay socket floating around in your toolbox,
    you're good to go. Break one of the lines to the gearmotor and wire
    the TDR up like this (view in fixed font or M$ (Micro$oft) Notepad):


    ` AC1 AC2
    ` o o
    ` | |
    ` | |
    ` | .-----------------------. |
    ` | | | |
    ` | 7| |2 |
    ` o-------o Recycling TDR o-------o
    ` | | | |
    ` | | | |
    ` | '-----------------------' |
    ` | |
    ` | 1 4 _ |
    ` | ||/ / \ |
    ` '-------------||---------o( M )o--------'
    ` /|| \_/
    ` TDR
    created by Andy´s ASCII (American Standard Code for Information
    Interchange)-Circuit v1.24.140803 Beta www.tech-chat.de

    It shouldn't matter which wire you open up here. This will save you
    about 90% of your $800 CAN (Canadian Dollars), and you'll get a one
    part, newbie-friendly solution that will work. During the time that
    the washing macine applies voltage to the motor, the TDR has power. It
    will start with an "ON" by using the N.C. (normally closed) contacts,
    which may be important if something else triggers on this cam. If you
    set both dials to their midpoints, you'll have 15 seconds on and 15
    off, which is a good place to start. In order to extend relay contact
    life, see if you can live with both pots full CW (clockwise), for 30
    seconds on and 30 seconds off. There are solid state recycling TDRs
    that will do the job for less, but this one is a good answer to your
    problem. It should last for years.

    For a self-described newbie, I don't think the old low voltage power
    supply powering a 555, a transistor and a relay is a good idea. Making
    line voltage stuff on a perfboard isn't newbie stuff. Also, once you
    gather the components and perfboard, construct it, test it, put it in
    an enclosure, and hook it up, it will probably end up costing more than
    the TDR, anyway.

    Still, this whole business seems like more hassle and money than it's
    worth. I'd rather just Google the proper timer motor. That is, unless
    replacement is such an SOB (Senate Office Building) that anything else
    would be preferrable. Or you've had so many hassles with the original
    hardware, barked your knuckles once or twice, and are so close to a
    real solution, that you'd rather try something else to get back at it
    and let it know who's boss. Been there. In which case, knock your
    socks off.

    Good luck
    Chris

    P.S. And by the way, there are many things worse than "Tax and Spend".
    One of them is "Borrow and Spend". At least you folks up north are
    paying for what you get -- down here we're all just putting it on the
    credit card and yoking up our kids and grandkids to pay for it with
    interest later. This will continue until the party's over. In these
    sad days, this is known as CFV (Conservative Family Values).

    Chris
     
  4. Chris

    Chris Guest

    Chris forgot to write:

    All that kidding around, and I didn't get to the part number. Sorry.

    The P&B part is CRB-48-70030, and goes by S&S of Nebraska p/n (KTD)
    CRB-48-70030. They've got it for $65.00 USD.

    The data sheet might be helpful, too. Here it is:

    http://relays.tycoelectronics.com/datasheets/CR_DS.pdf

    Good luck again, Mike.

    Chris
     
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