Elevator Controllers… The Brain of an Elevator
The controller is the brains of an elevator system. In the very old days operators were needed to start and stop the elevators and to go to whatever floor the rider needed to reach. A real human being slowed down, speeded up the elevator, applied the brake and made the adjustments to bring the car level at the floor. For those of you that think elevators are simple devices that just go up and down, this is the one that fits the bill.
In the late 1940’s manufacturers introduced automatic elevators that no longer needed an operator. Functions such as stopping, starting and changing directions were built in. This allowed the owner to reduce costs by eliminating the attendant and letting the public “drive” them selves to whatever destination they chose. Early elevator controls used a system of relays (switches) to make up a remarkable facsimile of todays’ computers. Although they were very simple and only performed a few functions the logic is essentially the same. A series of circuits is either in the on or off position and different combinations of on and off resulted in power being routed to different parts of the system to perform various functions. Microprocessors today use thousands of circuits etched on silicon to duplicate the same on off positions of the circuits.
As elevators became more widely used more circuits were added to enable the equipment to do more things. To reduce size labor and cost individual relays were employed to perform multiple tasks. For instance if relay R was the fourth in a series of circuits that were for a function such as fire recall, the same relay could be used as possibly the first in a series that controlled the re-leveling function. Even greater demand for functions caused the controllers to grow in size and complexity. As they grew more and more complex and each relay was responsible in a growing chain of functions servicing and repairing these became increasingly more difficult. If a technician added a circuit for something like an alarm bell for instance he could end up disabling another function such as door re-open. At this point anything more extensive than checking or changing out relays required the work of a higher level technician, also known as an adjuster. Of course the safety functions are critical and when any changes are made the circuit diagrams have to be carefully studied and the new additions cautiously planned so as not to disable or change any of the available tasks that the elevator is already wired to execute. I don’t know what percentage of relay based units are still out there but I believe that it’s probably greater than 50%.
In the eighties the elevator industry began incorporating printed circuit boards to carry out some of the tasks required. The boards enabled the manufacturers to cut manufacturing costs, reduce service labor time and pack more functions into a smaller space. A side benefit was reduction of heat in the machine room which you will see in my next posting, started to become crucial.
Until then…
If you have any questions, or comments please let me know. Some of your emails have been very entertaining. I have been thinking about possibly working on some software that can write your maintenance plan and tailor it specifically to your equipment and conditions. Please let me know if this is something you may be interested in. Also if there are any subjects you would like me to tackle next don’t hesitate to comment or email. Otherwise I plan to write a bit about elevator controllers in the next posting. For questions or comments please contact me at elevatorernie@hotmail.com.Thank You,
Ernie
Today’s quote is from W. C. Fields
“When doctors and undertakers meet, they wink at each other.”
