We had an opportunity at my old steam plant in Laughlin to replace the back-up reciprocating instrument air compressors dead 1960's era electronic sequencer & unloader. The factory wanted $300K for a turn-key project. We took the manuals, picked the plant operators brains, used the elementaries & wiring diagrams and an off-the-shelf $1500 Allen Bradley PLC and expansion module. The pressures & temps were 4/20mA signals, the controls were discrete inputs. 3 weeks and about $30K total parts & labor (after Management added "extras") we were done. The completed Sequencer Program ladder logic hard copy print out would apply to ANY PLC system, you just use their software plus your "roadmap" & make it happen.
Obsolete software is an obstacle only if you don't know the process equipment & requirements. The process tells you the logic & I/O needed. After that you just make the "new stuff" do the job. It ain't rocket science, and it needs to stay in-house. Farming out work like this just puts you right back where you started, everything becomes a black box understood only by "others" and you are screwed if it dies.
In the 80's I worked with Jim Mickey at Etiwanda Power Station. Jim was a self taught Old School "8th grade graduate" Instrument Technician that had created the entire steam plant electronic distributed controls system with off-the-shelf bits for about $250K in parts vs. $5M and many months offline for a 3rd party contract effort. He read manufacturer's instruction pamphlets for fun and he'd been doing plant controls instrumentation for years. It's all just tinker toys and working process knowledge.
Once the pressure, temp & distance signals are converted to digital I/O signals by the proper interface modules the rest is just figuring out what to do and when to do it. Modern PLCs have sequencers, counters, totalizers, etc. built in and simulation software to train/learn on. The "hard" job is to find a qualified, interested guy(s) to do it in-house. It does take concentration and an understanding of the process. The computer I/O & programming you'll learn if you are interested.
It sure sounded to me like you were suggesting a $1500 PLC, and three weeks of effort as an alternative to a $240 furnace main board.
Now I'm hearing about avoiding $300K factory solutions, and $5 million dollar consulting company proposals. That's quite a redirect, but you're right, it's pretty much the same "sell you on the glitzy features, and don't read the fine print until it's too late" concept as brought me in here.
I'm right in sync with the idea of DIY, but, there's just not enough time in anyone's life to convert all their late model appliances to documented contrivances that they have hand built. Something like a PLC may make sense for a high value, unique application, but for all the ordinary stuff my vote is for maintenance and continuation of the old tech, from the before the "only lasts the warantee period" era.
There's plenty of this stuff still around, made of real metal, with relay logic, and NOS parts are appear monthly on Ebay, at very reasonable prices, and offered up by the sons and granddaughters of the old business owners and technicians who squirreled the stuff away on shelves decades ago. In my opinion, they didn't really figure out how to reliably make planned obsolescence work, down to the component level until the 1990s. In the 70s and 80s, many companies were still building the best product they could.
Even if you did rebuild your appliance with a Raspberry Pi for a brain at considerable effort, you're still stuck with the poor quality of the components and systems. My american made fridge has lasted 34 years, and was probably 20 years old when I got it, free, with the purchase of my building. Runs long and strong on R-22. Who gets even a decade from a modern fridge, pumping R134a with a malasian compressor?
Topic: Electronic clutches (Read 2630 times)