Relay Control Systems

This isnt exactly a question about a PLC, but i was wondering if anyone knew of any useful places to gather information about some of the first uses of relay control systems. I am trying to gather information to construct a report about. Some information where relay control systems are still in use today would also be nice.

thanks for any help at all

Look at AT&T. Not sure if they were the first, but they certainly had many, including drums.
Look at Ford's first assembly line.

One of our production lines is still on relay control. It was built in the 60's and is still going. We just haven't got around to upgrading yet.

I also installed a relay contolled water pump station about three years ago. It was too simple a job for a PLC, although I would now probably use a smart relay to do the job.

Now my turn to ask a question, I was looking at the Pheonix Contact relays that we are using, and they are tiny. Only 5mm wide (0.2 inch). Looking at all the old photos of relay control and 30's/40's vintage computers, it seems the relays used then were much bigger. Would it be true that the relays available today are much smaller than those we had in the past?

Info on the web regarding the history of relay logic seems to be scant..

I did find this book, it has a chapter on industrial control, but no history:

http://www.andamooka.org/reader.pl?pgid=liecDigitalDIGI_toc

We maintain units that date back before 1920. The old old timers are still running, and provide us with good revenue for maintenance and callback$$$.... For the most part the logic relays are mounted piece-meal on a slate board, and use carbon stationary contacts with copper movables, and great big energy sucking coils. Back during this time my grandmother was pulling and plugging phone lines for ma bell along with 10,000 other rather young women. As per her, the phone system was ALL manual up till the mid 20's. So putting it together, elevators were automated before the phone system...

The elevators I'm speaking of usually had automatic leveling, and signal flag system in the car to tell the operator what floor somebody is waiting at and what direction they want to go.

The people at Bell Labs (sometime in the late 1930s) are credited with coming up with the rotary pulse stepper, which allowed a relay logic controller to count. Big Jump in automation. So if your OLD enough to have ever dialed a rotary dial phone, you'll hear it go da da da da...well this is the stepper at the local exchange stepping, eventually diverting your hardwire phone connection to the other party. At the local phone exchange they’re where something like 11 steppers for EACH phone number on that exchange. When I was a kid there was a rather large building on the corner of Mack & Cadiuex. On a quiet Sunday afternoon you could stand on the corner and hear the clacking from inside the building as people were dialing their phones..

The really big jump in came about the time of WWII. The Eniac computer used to calculate shell trajectory tables was commissioned in 1943 and used more then 10,000 vacuum tubes and 1500+ relays. The term BUG was coined when one of the techs discovered a moth caught between two relay contacts on this unit. "I fixed it" "What was wrong?" "There was a bug in the computer"

Also about that time Heddy Lammar, (Bombshell actress who played Dahlia to Victor Mature's Samson), came up with the idea of a timed drum that would be used to cause a transmitter and reciver to hop frequencies. However the idea was kept under wraps by the US Government for some time until it was re-invented.. Suffice it to say that she & her partner was one of the first to apply a drum control to an electrical apparatus. Not to say it wasn’t done by others, because she actually swiped the drum idea from a player piano, and applied it to the radio; but she was one of the early birds to think of it...

When I was a kid back in the 60s I had a great uncle who was like 100+ years old & died shortly after the 1st moon landing. This guy was really interesting. Apparently he made a living as a hired gun, but fell for this girl and had to get a more respectable job to convince her pops that he was worthy of her. So he retired in the early 50s from Boroughs in Detroit as an engineer. So between stories of Deadwood & Dodge City, he was the 1st person to show me a relay ladder diagram. Apparently just as the war in Europe was getting going, he was designing automated tool machining controllers using relays counters & drums rather then mechanical cams and such. Years later I discovered a general specification for design and documentation of relay control systems for the auto industry at the old Packard Plant in Detroit with his name on it as one of the authors. BTW I'm really glad I listened to all his stories and such, because he gave me all his "hardware" from his 1st "vocation", and told me the story of every notch on every barrel....(much to the chagrin of my mother as I was only 8 at the time)..

As far as I know, Potter Brumfield is widely credited with the first plug in relay back in the 50s, making things a WHOLE LOT easier...before that, in many cases you had to de-solder the relay to replace a contact or coil. Replacing a single contact on a single relay could take a few hours and required some patience and skill.

At least in the elevator industry hard-wired relay controllers were commonly installed new up to about 15 years ago. (Kinda slow to the punch..) Now days with all the features required by code that's no longer practical due to the fact that a smaller, less costly and more reliable PLC can replace thousands of relays, timers and counters etc...

In my experience all relay controls slowly became relegated from complex applications to only the simplest systems today. Today, if a logic application requires more then 4 or 5 relays and a few timers, it gets a small PLC instead.

That's my version of it anyway...

Now my turn to ask a question, I was looking at the Pheonix Contact relays that we are using, and they are tiny. Only 5mm wide (0.2 inch). Looking at all the old photos of relay control and 30's/40's vintage computers, it seems the relays used then were much bigger. Would it be true that the relays available today are much smaller than those we had in the past?

Click to expand...

The answer to the size question is yes. Finder have a 5mm relay and I believe Omron now have one. The normal relays I use are 11mm wide from Omron - G2R series - and are available in 1 and 2 pole versions.

As we know Relay is the electro-mechanical switch, when the coil gets energised (get power) magnetic effect comes in to play & closes the contact or opens the contact. Relays are older version of transistor, which we use is our Relay o/p module, therefore many people do call that as realy o/p module, but actually speaking each point inside the module have a npn (typically) transistor ckt in it, it behaves same as the relays do. Only difference is that it does not have any moving device like realys ....therefore greater realiability & longer life. But we cannot use transistor at high frequency or high v/g. So whenever we want ckt switching at high v/g relays we use relays.