Deciding scheme for control circuit

[Obmar]

A motto (of Rodalco if I remember right) says “there are more than one way to go to Rome”. Likewise there are often more than one ways to design a control system. I would like to invite wise guys of this forum to give some thought to this ‘techno-philosophical’ subject. I will explain what I mean:

A control circuit (of an instrument or a small machine) can be designed using discrete components (like gates, timers, flip-flops etc) or PLC or PC with high-level software. The tendency is to use the system that you are more familiar with. An electronics guy will try building complex circuit for a simple logical requirement, while a computer guy will write software even for switching off a motor by a signal from a limit switch. The optimum must be lying somewhere in between.

What is this limit? At what level of complexity, the PLC/PC based control becomes easier and cheaper than hardwired circuit? Is microprocessor based control always the best option? What is in interest of the not-much-technical user?

 

[Nigel Goodwin]

You've completely missed the real answer to your question - for many years now micro-controllers have taken over almost all those type of applications. Even PLC's these days are just another micro-controller application!.

 

[Obmar]

OK. If this is such an irrelevant point, let us drop it. I agree that microprocessors have taken over long back. But there are still thousands out there (mainly from older generation) who are not grown with and hence are not very comfortable with the processor-based systems. I have seen their confusion and think that perhaps we can give them benifit of our knowledge. But ....

 

[Nigel Goodwin]

OK. If this is such an irrelevant point, let us drop it. I agree that microprocessors have taken over long back.

You're not reading what I said! - I said MICRO-CONTROLLERS not micro-processors - a very different device, and it's micro-controllers that have revolutionised electronics over the last 15-20 years or so.

 

[jpanhalt]

What is this limit? At what level of complexity, the PLC/PC based control becomes easier and cheaper than hardwired circuit? Is microprocessor based control always the best option? What is in interest of the not-much-technical user?

There doesn't seem to be a limit. Light dimmers in autos that could use a single pot or one transistor and a pot have been replaced with microcontrollers.

It's progress.

However, one can still find enjoyment in using older methods, such as riding horses and hand woodworking tools. So it still is with discrete electronic components. Unfortunately, the economics of producing some components, particularly IC's, that are compliant with modern pollution standards is such that they may not exist much longer. John

 

[Super_voip]

The auto light dimmer example is a classic case of improve ment, the switches are more reliable than a pot, the pots are harder to solder, weigh more and are therefore subject to more pressure from vibration and G forces.
As for the simple pleasure of riding horses, a lot of background has to go on before you mount the horse. The shoes need replacing, the stable mucked out, feed the horse or the horse bought in from the paddock, and that's before the saddle blanket is even looked at.