So my washing machine's (SpeedQueen) mechanical timer has died (again) and they want a silly amount of money for a new one.
I'm sure it wouldn't take me long to knock up the same functionality on a microcontroller.
The "Make:" controller
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would be ideal, except it is not much cheaper than the timer and way more powerful / featureful than I need.
What suggestions for a cheap / easy to program / electrically robust microcontroller complete development board that would do the job without having to muck about much with the hardware?
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John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : john.carter@tait.co.nz
New Zealand
Really? Do you have a definition of the timing sequence, I/O specifications and the high-voltage, high-current outputs to control the solenoid valves, read the water level sensor, and respond to user inputs?
PLEASE don't tell me you think you can control a washing machine without mucking about with the hardware! ;-) I think you're going to get very familiar with the local laundromat.
Honestly, I wouldn't do that. A local junk yard might be the easier path to obtain a timer. Also, it would be kind of embarrassing when the insurance adjuster stands there in his rubber galoshes one day and asks "How'd that mess happen?" "Oh, must have been some power supply glitch."
If you want to learn uC stuff on a budget look at the Texas EZ430. Mine was $20 and you can get MSP430F2x series devices in DIP packages.
Timing tolerances I figure are pretty crude anyway. Give or Take a minute or two.
I/O specs I hope to find a schematic somewhere to read, or measure with a multimeter.
I can't believe I'm the first person on the planet wanting to switch high current 230V AC. After all every appliance in the ex-British Empire does that. ie. Hopefully some one has a little General purpose application board with a microcontroller and bunch of relays all pre-wired and working.
The machine is 15 years old, and this part has failed twice. So I'm damned if I'm going to pay a large proportion of the price of a brand new washing machine to repair it, I figure the pumps and the engine are due to go about now anyway.
So I will let it limp along, and if it dies (or my tinkering gives it a fast humane death) I will simply buy a new one.
If I find the general purpose MCU & relay board and fix it, I will have learnt something handy and had some fun.
I have done a lot of software before, embedded as well. It's just that I don't usually do the hardware end of the projects.
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John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : john.carter@tait.co.nz
New Zealand
Very tough because some of the wires go to magic devices that could actually be hidden safety thermostats, pressure sensors etc. Not a good thing at all if you'd miss the function of one of these. On the ohmmeter you'd read a short or an open but you wouldn't know what's really behind that.
There are some GP boards like that but all the ones I ever came across were well above US$100. Without the compiler software and all that.
I have a washer and dryer that I inherited from my deceased mother about
20 years ago. They are still running. I replaced the timer in the washer about 3 years ago. IIRC, the replacement timer cost about $70US. That's a lot less than the cost of a new washer. The timer has about 8 connected wires---I think they all carry the US standard
110VAC. Some of the wires feed back to the clockwork motor to halt the timing until the tub is full (We have low water pressure and that can take a long time). I suspect that you will need a minimum of 6 or 7 AC controls:
Clockwork motor
Motor low speed or agitator
Motor high speed or spin cycle
Tub brake for spin cycle (to halt spin if lid is opened)--this may be external to the timer, though.
5 Hot water solenoid
6 Cold water Solenoid
7 Bleach release solenoid (not on all machines, though)
I don't know tht you'll find a general purpose MCU board to handle all that. In addition, the timer receives inputs from the water temperature selector, cycle selector (color, white, delicate, etc, etc.) Some of this is done by simply rotating the switch to a preset position. You will need some other sort of user interface. You will also have to make sure it will fit in the space of the timer switch and will have a proper power supply. It also have to handle the temperature, humidity, and vibration that the washer will experience. You will need to control power supply transients and EMI that accompany the the control of the rather large motors in these machines.
Given all these constraints, I truly admire the engineers who have designed these machines to work for 20 years between overhauls or service calls.
On my washing machine I need 3 solenoids for the motor because it runs in 2 directions and centrifuge. (These were added to bypass high power from the timer, also a solenoid for bypassing the theromostat was added) Also add a solenoid for the pump or water release valve to let the water out of the machine again. Also my machine has 2 switches for water level (low high) for different kind of textiles. The machine runs here from 1966 (it was second hand) it had a new timer about 20 years ago, at that time my father added the solenoids so the timer would last longer this time ;-)
Oh, I don't know. Don't want to leave the water running too long.
A number of years ago I had to replace the mechanical timer controller in a Kenmore dryer. The schematic pasted inside the dryer shows where wires go but not what is happening inside magic boxes. It took me a while to conclude that a switch inside the timer was not switching. To finally believe I understood what was happening well enough to jumper around the timer and prove my theory.
This was a 230V dryer. The washer is only 115V.
May be harder than you think. Was once thinking I should be able to easily find an embedded board with about 24 channels of A/D. Decided it would be easier to take a general purpose USB DAQ and connect to CPU with USB if one absolutely must buy-not-build. Or move up to an embedded PC.
In my situation Sears wanted $100 for the part, plus shipping, plus tax. The local Sears did not or would not stock the part. Four local independent appliance parts and service stores all had the part for $50 to $65. The $50 part clearly came off the same assembly line as the original, but had one extra terminal and a note in the box stating when
-2 was used where -1 was original, the extra terminal was to be No Connect.
The unit is now 18 years old and will not be replaced with a Kenmore. It has served well but others are trying harder than Sears/K-Mart.
From that angle, "Go for it." But if your time is worth $1/hour the cheapest thing to do is buy the replacement part.
For those in USA , BG Micro sells $10 and $3 SSR's that can switch 30 and 6 amps ...
Forth does relays faster than any HLL . it does no compile nor interpret , it records your keystroke into adictionary , ready for testing in minutes . No assembly , no C++ , no compilers , no wasted time . If you get bogged down , then you have
a Luddite creation , wrongly named Forth .
Forth has NO manuals ( dont need any ) ..
You learn Everything you need , in Forth ,, at the terminal , in minutes .
Forth is more powerfull and less time than any language .
for more than 30 years , Forth programmers have successfuly connected hardware to their CPUs in minutes ! Not even industrial Basic is easier to learn ...
Having read through the other responses all I can say is don't be such a cheapskate and go buy a new washing machine. At 15 years old it will likely have a number of potential problems that will cost more to fix, apart from the controller. A new machine is likely to be more energy efficient and safer than whatever you come up with (or at least the company can be sued if their machine burns your house down - seek out Candy for that story).
As for learning to do embedded control systems, buy a cheap processor evaluation system and go play with that for a bit, preferably at lower power levels and on something that will not cause a problem with safety issues.
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Paul E. Bennett ....................
Forth based HIDECS Consultancy .....
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
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FORTH is an abomination in the sight of the Lord. In the days when C compilers cost $2000, compiled so slowly you could take a French lunch break and still come back before it finished, and produced 32k of code for a "hello world" that took 30 seconds to run, FORTH was useful. But I swore I'd give it up after struggling with out-of-control stacks made my life a misery. Only use FORTH if you're happy walking backwards while juggling chainsaws.
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