Monitoring the washing machine

Introduction and problem definition

The washing machine and the laundry dryer are both located in the attic. As both machines are controlled by microcontrollers and sensors you never know how much time they will take to finish their job. There are two steep stairs from the first floor to the attic and we got tired of climbing the stairs just to see that the machines where still running.

An other problem is that we live in an old house where the powerlines are not strong enough to run both machines simultaneously. To be more specific, the heating elements of both machines can not be 'on' at the same time.

Some explorative experiments wit a PC with a built in 14 bit bipolar analog to digital converter showed that it is possible to pic up a power signal from a coil around one phase of the machines power supply and use that signal in a PC.

So now it was clear that some 'calculating device' could produce a 'signalling' which would let us know the essential details about the washing and drying activities in the attic. The only question to be solved was how to bring the signals from the monitoring system down to the first and second floor.

Washing machine and monitoring system Note the thin white cable comming from the glass door of the washing machine. On the machines side there is a thermometer which is connected to a Remote Sensor unit. This way the temperature of the machine can be monitored during the washing cycle. The Krokus Remote Sensor is a recent system and is apart from the monitor in this project.

The washing machine

Here is the washing machine with on the right the edge of the laundry dryer. In front of the mirror, to the left of the bottles, there is a small cabinet, a Remote Sensor unit, and a big cabinet: the washingmachine monitoring system.

For the monitoring system the CControl units are used because they are complete and closed boxes which fitted well to my virtually zero experience with microcontrollers at that time. The units use a 132.45 kHz protocol for transferring data through mains which solves the problem of getting the signals to the right places downstairs. This choice was based on the expectation that the units would be able to do their job AND that I would be able to put the bits and pieces together to a working system.

If I had to redo the system now It would be a lot smaller and certainly a lot less expensive. But I believe at that time it was the best I could do. It works and it goes on monitoring our washing process every week !!

The monitoring system On the left are the CControl units. The big unit on top has the micro controller onboard. It gets the signals from the machines, analyses them and then sends the results to the lower unit, the transmitter. The transmitter then sends the code over the mains network to the receivers.

The CControl monitoring system

Now the box is open you can see how bulky CControl units are, they are on the left and mounted vertically. On the right you see the signal conditioners for both input channels and, towards the bottom, the power supply for the conditioners. The CControl units have their own supplies.

In fact the CControl gets signals proportional to the current draw of both washing machine and laundry dryer. From those signals it knows the current and from that the system can tell when a motor is running and when a heater is on or, finally, when the process is finished. It allso remembers the history of the current peaks so it can tell if the heater has been on, if the washing machine has warmed up and is finished using the heater the laundry dryer can be turned on :-).

The software for the CControl controller unit has been developed using an analog signal simulator. Using this simulator the time to run a total cycle of washing and drying could be reduced from several hours to only a few minutes.

After simulating and testing the system worked 'right ot of the box' and it works without any serious problem for over 3 years now.

The washing mashine signalling device The device is seemly mounted between our wine. It is well visible yet not too obvious.

The washing mashine signalling device in action. From left to right the LED's mean: 1-washing mashine is running 2-heating is finished and 3-laundry dryer is running. This little cabinet can be placed anywhere, as long as there is a mains supply for power and data transmission.

Trouble shooting using our own tools

We had some trouble with the washing mashine some time ago. We noticed that LED 2 wouldn't light sometimes and first we investigated the functioning of the monitoring system. That was OK, so when do we start trusting our own systems first :-).

Investigation of the washing machines behaviour showed that about 1 out of 4 or 5 times the machine did not get warm. Sometimes the machine worked OK for a while and then the problem was there again.

This is not an easy kind of problem but with the use of the monitoring system connected to a datalogger and the brand new Krokus Remote Sensor system we where able to track down the problem to a loose contact in the electronics part of the washing machine.

After the loose contact was fixed the washing machine runs like new !!

A temerature curve (RED line). This is a typical curve for the washing mashine heating to 40 degree C. First you see a drop in temperature when the fresh water comes in and, after 10 minutes, temperature starts rising at a rate of about 3 degrees per minute until the final temperature level is reached.

This is the new Krokus B with Bluetooh module. With this Krokus you can measure three standard parameters,T ,RH and light, plus an arbitrary value and transmit them to another device in another location which has to be within range (max 100 meters).

Bromsmurfsite