>-----Original Message-----
>From: pic microcontroller discussion list
>[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Howard Winter
>Sent: 02 June 2004 20:49
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [OT:] RS232/Pic controlled washing machine project
>
>
>Dom,
>
>Nice project - I'd always wondered about doing something similar, and I
say:  Respect!  for actually doing it!
>:-)
>
>On Wed, 2 Jun 2004 18:39:01 +0100, Dominic Stratten wrote:
>
>> Funny you should say that but mine now does three rinse cycles - I was
never
>> convinced it used to get all the detergent out of my washing. It also
spins
>> them between rinses to it gets as much of the old water out as possible.
>
>I had a washing machine that did 6 (six!) quick rinse-spin cycles, then
followed with a deep rinse.  I've
>never had problems with allergy to detergent at home!  (I did once staying
at my brother's place, where their
>washing machine just does the usual not-very-effective rinse...
>
>How did you find out how to "drive" the machine?  Did you have
documentation on its control system?
>
>Cheers,
>
>Howard Winter
>St.Albans, Herts.
>
>--

Hi Howard

I had no documentation at all on how to drive the machine. I reverse
engineered the existing controller to find out how the windings of the motor
were controlled/switched. It uses a large induction motor with two sets of
windings. One set for the wash (low speed high torque) and one set for the
spin (high speed low torque). The direction of the motor was controlled by
using a relay to swap over the terminals of the motor start/run capacitor.
The speed of the motor was controlled by a simple triac circuit that
switched the triac on at a certain part of the mains cycle depending on the
torque required of the motor. The inherent "slip" of the induction motor is
used to slow the motor down under load along with the firing of the triac.

It took me about 2 weeks start to finish to research motor drive techniques
on the net, build the controller and driver board (and
etch/drill/solder/drive to RS components to pick the bits up), program the
Pic and get my first wash load done. I used an LM2917 frequency to voltage
IC hooked to AD0 on the 18F pic for the speed sensing (I didnt fancy
overloading the PIC as I was already using a few interrupts to do other
things) and AD1 on the pic for the thermistor.

There were a few problems with the LM2917 picking up the mains hum on the
motor when the drum was stationary but I found that by giving the drum a
quick spin before checking its speed then it all worked well.

Other problems were the Pic resetting occasionally when the relays were
triggered and the temperature sensing is not very accurate when the drum is
rotating (interference from the motor again) but this was all taken care of
in software in the end.

Unfortunately (or fortunately depending on how you look at it) the new
washing machine is turning up on Friday courtesy of the missus so this one
is going to be scrapped tomorrow and the bits I bought for it removed :-(

It was good fun though and if it wasnt for the missus constantly on at me to
get something working so we could have clean clothes, it would have been a
lot more fun :-)

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