For test purposes I have set up a system with a number of the cheapest possible 433MHz wireless switches that turn on some lights in our house when the sun goes down and turn them off around 2 in the night. This is controlled by a VSCP daemon. Not a very exciting installation for sure, many have this kind of thing installed and the VSCP daemon is definitely a lot of power wasted for this tiny functionality.
But the job is done. When VSCP calculates that the sun has gone down lights go on and at the scheduled turn off time they go off. I even have some lamps out at the garage (30 meters from the controller) that is switched this way. It works well. Most of the time that is. I don’t know why, maybe it is dependent on different weather conditions, but sometimes a lamp will not tun on or turn off. One problem here of course being that the cheap 433MHz switches are communicating one way. The controlling system does not actually get a response back from the switching device telling that it actually did the switch. A two way system would definitely improve things. But it’s good enough. 99% of the time lamps go on and of as they should. Perfectly OK for this type of setup.
But then for about a month ago things started to work very badly. Most of the time switches did not switch on. It was more like 10% good operation instead of 99%. After replacing everything and testing all hardware, I am the type that first blame my own systems when something goes wrong, I notices that also the hand controllers that comes with the switches did not work well. For some parts of the house I had to go as close as a few decimetres to the switch to make it controllable. Changing batteries did not improve anything.
The question is of course. What was this? I radio engineer I know told me I probably have something disturbing my system. To see an prove that I needed a spectrum analyser, which I did not have of course. But to , again, be sure that there was not any of my equipment that made this happen I turned off everything I could think of in the house. But things did not improve. This came from some external source.
The other day things started to work again. Just like that. It all lasted for almost a month. I still have no clue what caused it. Probably at that time a disturbing source was turned off. A source unknown to me.
Now this was no big deal. We can turn on lamps by hand still in this house. And if we don’t, nothing bad happens. But we also know that wireless systems are used for elderly alarm systems, house control systems, burglar alarms and things like that. What had happened in this scenario if I was an elderly that had fallen and pushed the emergency button on my wristband? Or if I had my sensors in my alarm system connected wireless and some burglar decided to grab my computers (and our stack of gold) just this month. And in the case of the wristband and probably for most sensors a two way system would not help much. Things would be bad.
It is very easy to build a scrambler that make any ISM wireless system go useless. I don’t think criminals are less aware of that fact then the rest of us. So burglar alarms, or any alarm system, should probably not use wireless sensors at all to be safe. But they do.
There are solutions. A controller can go out and check sensors from time to time and alarm if communication is not working. Battery devices would love that. And people love to change batteries after all. But it would at least improve the systems. But still people can come into our recent position. Suddenly the system does not work. Everything individually appears to be working. Switching gear does not help. It is “something unknown in the air” causing the problem. What to do?
Yes wireless system are convenient. But sometimes cables still are superior. We must just remember that when we run blindly after everyone else in the same direction as they run.