The refrigerator again. It takes more time then expected of course. It always do. This time because I have a lot of other things to attend to at the moment. I understand if you ask some questions about this project. So I answer them here (before you actually ask them)
Why this project?
Our refrigerator broke down two weeks ago. And we need one also in my family. Of course we do, open source programmers may not afford much buying stuff but we also want our milk to be cold. Luckily it is winter here now and we have some other storage that is at about four/five degrees so it is no immediate panic, but as weather is getting better (the spring is coming) this is not a good long-term solution.
When our fridge broke down some years ago I decided to try to rescue it and if it was possible I would take standard VSCP modules to do so. The compressor was OK and if it is this is a simple project mostly. This project has worked perfectly well since then and became a nice VSCP demo project.
Yes, Yes, YES it’s an overkill using VSCP standard modules for this. An Arduino or some other simple board would have done the job. But I wanted to use the modules to see if they did their job also over time. The best way to actually see if things are working the way you thought is to put them in some critical system in your house (the heating in our house is already controlled this way). If there is some bugs or design problems things will be solved by necessity. To have them in a demo system on a workbench is just not the same thing.
So for the refrigerator the first question was to check if the compressor still worked. If it was dead it is just a pieces of junk and not a refrigerator. But just as with the fridge it was the control logic that had broken also this time. Make me wonder how many perfectly fine refrigerators/fridges are thrown away out there that could have new control added for a few bucks and do the job they were designed for for many years more.
As with the fridge I decided to go for standard VSCP modules for the refrigerator project to make it a demo project. It is easier this time as I have the CAN4VSCP bus connected to the fridge that stands next to the refrigerator. I just need to connect the two together.
So I put in a Kelvin NTC10K module and a Bejing I/O module in the refrigerator and hook it up to the CAN4VSCP bus so I am able to monitor temperatures and change temperature settings and get possible alarms from the unit. As with all VSCP modules they form a self-contained unit. There is actually no need for a server after they have been configured. The second video here show the configuration process and the first show how the modules are connected together.
The Kelvin NTC 10K module is a module that one can connect a couple of temperature sensors to. It can be programmed to alarm at low and high temperatures and as in this case turn on and off things when certain temperature thresholds are reached.
In the fridge project a Paris module is used together with the Kelvin NTC module. The Paris module is constructed to control relays and have all the electronics on board to do that. It also include protection timers and a lot more.
In the refrigerator project I decided to use the Beijing module instead of the Paris module. Mostly because it did not matter to have standard I/O channels as I use a solid state relay to switch on and off the compressor, but my main reason was that I got a chance to use it in a real life demo system.
So the Kelvin NTC10K module sense the temperature in the refrigerator and the Beijing module is used to switch the compressor on or off and to sense if the refrigerator door is open or not and if it is light the lamp inside the box.
It is possible to sound s siren if the door to the refrigerator is opened between midnight and six in the morning. But some things just hit you right in the face so I will not implement that functionality. At least not now.
Connect cables and putting it in the refrigerator where the old control logic was located. No programming is needed just configuration. The second video above show a bit of this configuration but I will go through it in a more precise way in a future post. Hopefully things will work as thy should tomorrow. The VCSP modules are very flexible and can be used in most control situations to form self-contained systems that can be connected together and be connected to the world in a safe and secure way.