When I was young, like back in the 1970s I read articles talking about the benefits of converting from Analog to Digital, the revolution that will spread through the world and into each and every crevice of our lives. An example given was a washing machine and how much easier it would be to have it controlled by a computer instead of switches and relays. That instead of filling with water until a full-sensor switched the valve off, it would wire the water level sensor into a digital box that would then activate to open or close the water fill valve.
Well the year is 2019 and I still have an old analog washing machine and it works fine with its switches and relays. It even has four wash modes, three water levels, and an optional extra-rinse phase. I did not see the advantage.
What I recently realized about those old articles was they missed the point; sure analog works fine, for now. With the current level of sophistication the clock driven switches of the washing machine works fine. But once you start adding sensors and controls and requirements of operation, the complexity of relays and wires and switches, the rat’s nest of wires, quickly spirals out of control and becomes unmanageable.
For example, back then, my step-father Doug designed an alarm system for our house. It had time-delay relays and and locking relays and switches and regular relays and lights and was a glorious creation. But he scrapped it for a Radio Shack system that was digital because it was just too complex to get it to work the way he wanted it to work. And changing how it worked required rebuilding it completely, unsoldering the wires and relays and switches.
Cars are another great example; it used to be there was just the ignition switch that ran from the battery to the starter and that worked fine. But modern cars it requires you to have the brake pedal depressed and the transmission in park. Wires now had to run wires back and forth and the brake light switch down by the pedal has to be wired in to do so much more and sometimes it was a matter of ‘when it is off’ and other times it was ‘when it is on’. A low level of complexity can be managed with switches and relays and wires but add just couple more and it becomes unmanageable.
The solution is to run all the sensors and switches directly into a computer that has outputs to control every device or control. From there the software controls what does what depending upon the situation. So, when you wire the brake-light switch into a computer you can just reprogram it to add features like ‘tap the brake pedal to close the door’ (the Tesla X does this). It is relatively easy to write an involved if-then-if-not-then-else conditional. And instead of running all the door-open switches in series to the dome light you run each one to the computer and one of the outputs would be the dome light, this way you can also determine which door is ajar and display that on the dash.
My next washing machine will have sensors that measure how big the load is, how dirty it is, factors in the water quality and do a better job of washing my clothes. That is the advantage.