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


Mike Westbye wrote:
> 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.

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

.

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