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General Category => Your projects => Topic started by: Harhus on September 28, 2012, 19:41:46 PM

Title: Washing machine parts simulator
Post by: Harhus on September 28, 2012, 19:41:46 PM
Well i have a friend that opened a store for repairing washing machines and he t\started fixing the electronics for those and sometimes i jump in and help him out when hes stuck long story short....

what hes been asking me to make is a parts simulator, now let me explain what i mean. Sometimes he gets the whole machine and its easy to test the board if its working since all of them (more like majority) have test programs but sometimes he gets only the electronic board and he cant really test it unless he has installation and parts so far hes been doing it like this he ripped off installation cables and connect motor, hydrostat, electric valves, NTC probe, 15W light bulb for the heater, drain pump, door interlock. And it gets messy since he needs to rewire everything again when he wants to test another board, mainly because of the connectors, motor and door interlock.

now let me explain how test program works

when u start test program for example on a Beko washing machine it goes like this
it locks door
u oress start and it starts spinning motor in one direction and starts drain pump 
u press start again now it starts spinning motor in the other direction keeping the drain pump on
press start again starts centrifuge  still keeping the drain pump on
pressing start will start 1 of the electric valves
pressing start will start the 2nd electric valve
start again starts both at the same time
now hydrostat should be switched if its in water it will be auto but if u test it with installation u would have to blow in hydrostat hose and switch it on and now u bend the hose so u keep it switched.
now pressing start will start heater ( in installation case a light buld )
next start will drain the water out and this is a complete test program

Now i had some idea but maybe someone will suggest something better
for door interlock i would use a switch
for hydrostat again switch
electric valves 1 and 2 2xLED on 240V
Drain pump LED on 240V
2xLED for motor left and right and i heavent really tought how to simulate taho generator but i never seen a board that has failed electronic part of the taho in 99% of the time its a magnet in it or someone played smart and rewired it to 240V line and fried it or the triac shorted but everyone checks the triacs first in hope of an easy fix :P
for NTC Probes a potentiometer of 20k is fine ( any value above 4k is fine unless a test program waits for ntc probe then u can vary resistor)
again LED for heater and with all the LEDs u can host a rave party

this is a "quick" solution so he can use just a connector label them and put then on some standard connectors to plug it in this board
advantages of this would be smaller size and test cables can be pre-wired 

thou i would like opinions how a door lock and hydrostat can be automated i was thinking on sensing when the both valves are on and let them on for 10 sec then it will switch ( not mechanicly)

and for lock as soon as it gets 240V switch and keep it swiched until power is lost

i know it looks stupid but yeah i have weird friends :P
Title: Re: Washing machine parts simulator
Post by: kam on September 30, 2012, 20:39:52 PM
well, i read somewhere once "mechanics loves simplicity because it works". Make it simpler, since (as far as i understand) it does not need to be complex at all. Testing 2-3 boards per day wont be a problem with "manual" operation of door switch and hydrostat.

I only have one remark on this: Solenoids are inductance loads, which act absolutely differently from LEDs. A recent problem that i had once was with a motor on a relay.  I tested the circuit with an LED first, and i was totally sure that everything worked well, until i plugged the motor in - MAYHEM!

So, i suggest that instead of simple LEDs, you can have transformers or other sort of coils to simulate an inductive load. A broken flyback diode on the board will not show it's ugly face if you simply test it with an LED - and usually diodes and high current components fail first due to stress. A degraded mosfet may fail when it drives a high current motor, but it will act normally with a 20mA LED. Trust me - i faced this situation when i was studying about transistors. I degraded a transistor (under controlled situations with heat and current) and tested it to see the results. Noticeable results were only visible under heavy stress.

Some time ago, when i was making my keycode lock, i faced a problem with the PIC. I could not have sleep current less than 2mA... I tried everything, and i had to ask microchip for this. They told me that the PIC was probably degraded from static electricity - and YES they were correct. I replaced the PIC, uploaded the very same code, and ALAS! 16 micro-amperes.

In short - If failed part is a nightmare - a degraded part is a nightmare on Elm street...