Exploring an Otis Elevator button interface PCB

[@andreasstrom6391]

The board you have there is a general i/o board , it can be programmed to output / input any function to the controller , firealarm input, switch on lights on landing floor via an external relay and so on. There is an relay version of this i/o board aswell. When doing modernisation on older elevators (new controller with old door drives for example) we use this board to simulate the i/o signals needed to get the old door drive to work with the new controller.

[@JansenYong1]

Yep exactly. Everything is software defined now. Easier to build and cheaper to produce I think

[@LordDecapo]

Thanks for this! haven't come across this board before. Will know now incase i do :D

[@miguelquazar883]

@Crafts and other Stuff Its possible. These boards can do some weird things when they are addressed improperly. Just the other day I saw one with a closed circuit on the board that was not supposed to be. It was brand new and was causing a lot of troubleshooting and lots of blown fuses. Finally found the the issue. But like I said these things can make things act up. But if it fails or creates conflict eventually a proper working elevator that uses these should shut itself down. The problem you are mentioning sounds like an issue with the electronic eye that is used for sensing people walking in and out of the cab. I will not get into detail 🤐

[@Mark_from_IT]

Thank you for posting! I was just laying here feeling lonely and depressed. Now I have 12 mins of Clive to calm me down.

[@briandeschene8424]

And remember: Most people would think it completely normal to re-watch a television program or movie they’d already seen. So to for KZbin videos. If you treat Big Clive’s postings like them, you just doubled your viewing pleasure and don’t have to wait for a new posting to not be depressed. Cheers.

[@lironmtnranch4765]

I had a longtime client who was in the elevator and escalator business; wild alcoholic guy who was full of colorful stories about his trade. There were always cool elevator buttons, panels, and other parts in his car. Three interesting things he told me. Escalator steps have teflon sliders in the bottom. If one of these is lost for some reason, "Aluminum doesn't really scrape, it *smears.* This causes damage to the entire track and rapidly wears *all* the teflon sliders on that side. The bill for fixing the system after one $10 slider is lost ran well into five figures. Second, if you see an escalator step that looks wrong relative to the others, do not get on it. If you see an elevator that the doors open while the car is still significantly misaligned with the floor, it probably means at least one safety switch has been bypassed instead of correctly repaired, so really don't get on. The last imagine being told in a rough cigarette voice, like a cartoon villain. "You know the little frame with the permit under glass you see in every elevator, with the weight limit on it? We actually test it by loading that amount of weight into it. It takes two vans and four guys with carts a couple of hours to load and unload the lead weights. Then the car is raised to an upper floor, the cables are disconnected, and the inspector says, "OK boys, cut 'er loose!" The elevator has to completely stop within X number of feet on the emergency braking system. Sometimes it doesn't catch! The car will plummet aaaallll the way down to the basement with a CRAAAASH you can feel way up at the top! Dust and sparks and shit come wafting up out of the shaft, and the inspector just goes, 'OK, call me when you're ready for the reinspection!'" Bonus one: Due to the counterweight, falling UP is a rare but actual danger. Bonus two, the techs HATED any work in the bottom of the shaft. They always had to go in first with bleach spray bottles on the end of a hose and wash the whole thing down. Turns out SO many people pee in elevators! A given in ones that homeless people can access 24h, but universal even in ritzy high rises.

[@RS-Amsterdam]

And don't forget, If the elevator is on the ground floor and when the doors open you see a bunch of corpses laying on top of each other covered in blood .... take the other elevator !!

[@straightpipediesel]

The counterweight (found on traction elevators) is 1/2 the maximum weight of the cab. The idea is to minimize the necessary friction on the sheaves, which minimizes the number of ropes needed. Therefore, if the car is lightly loaded, going up uses less power (and may even regen power into the grid) than going down, and so you should take the elevator up and stairs down.

[@brianleeper5737]

Another interesting thing is the reason why there's often a sign saying "LEAVE NO JUMPERS" in the elevator machine room. Major accidents have happened because a safety circuit was bypassed with a jumper for testing, and was left in place when it should have been removed.

[@Dime_Bar]

@@brianleeper5737 was it a woolly jumper?

[@brianleeper5737]

@@Dime_Bar Wire jumper.

[@iconoclad]

Hint: I used to use a piece of cooking foil clipped to one of my meter leads to quickly identity the general area that a trace has run to.

[@bobert4522]

Alternatively, stripping a piece of wire and splaying the individual strands into a line makes a very good trace… tracer.

[@jakp8777]

Otis Elevators has a test elevator shaft in Southington, Connecticut right off the freeway and not far from where they are engineered. It’s about 5-7 floors tall and just a square concrete elevator shaft.

[@straightpipediesel]

Being British, Big Clive would know of the Express Lift Tower in Northampton. It was actually abandoned and functionally replaced by the tower you mention after the Express Lift Company was taken over by Otis.

[@piratetv1]

That's only 5-7 floors? It looks so tall from the street

[@jakp8777]

@@piratetv1 it’s not that tall. Not much benefit in having it super tall.

[@jakp8777]

@@straightpipediesel so testing was done in England but now Connecticut?

[@dashcamandy2242]

I completely forgot about that until I read your comment. I've driven past it a few times, but since I'm rarely in that end of the state, it slipped my mind. I remember hearing about the fire on the news.

[@brian9731]

Regarding any wire acting as an antenna/aerial - I worked on an access control system in a large TV studio complex. In a few places, doors would spontaneously unlock as frequently as every few minutes. The system would register the pressing of a Request-to-exit button except it hadn't been pressed. We eventually put it down to RF or electrical interference from high current cables in the vicinity. Using earthed/grounded screened cables worked in some locations but not others and using a small capacitor helped - to "slug" out the input but again, not always. A bloody nightmare all told. I have only come across anything similar on a house alarm where the house was near the London underground. Years later, I bought a house by the Underground - all my alarm circuits are wired in screened cable and I have no problems.

[@Anamnesia]

The "smart" KONE lifts in our building have Manual Call Points with a large numeric keypad, where you call the floor number you wish to go to, the the lift system figures out which path you need to take. For example; If you're on Level 4 & press '1' & '2' (for Level 12), then one of four low-rise lifts will be called to your floor. Once inside the low-rise lift takes you to Level-9 (transition level) & the internal Lift display will tell you which high-rise lift has been called to meet you on Level-9 so you can transition you to get to your final destination. The entire Lift system is quite "intelligent", but that's just a brief description on how the "smart" lift works. BUT, one thing the Building Owner has discovered since switching from their KONE maintenance contract, to a different Lift maintenance company is; KONE have "Chipped" their switches! Meaning: If a button 'fails', you have to buy a KONE button in order to replace the faulty keypad keyswitch!

[@gordonborsboom7460]

Learned this from Apple perhaps?

[@bigclivedotcom]

Kone are notorious for locking their systems when they lose a maintenance contract. Fortunately the geeks in the industry have ways around that.

[@mrfrenzy.]

Some italian made entrance door openers do this. The installer can set a pin code which means no one else can service the unit. Often times the service contract is so outrageous the building owners will scrap the units and replace them with another brand.

[@ChuckyF711]

@@bigclivedotcom Kone, like all major players in the industry, have their own unique control methods (Otis RS14 for example..) It’s no harder to work on a Kone lift than any other (perhaps easier if know what doing). All that locked out is the ability to change parameters not the fault and general diagnostics.

[@rolfs2165]

My university got a new control system for the main building, where you select your destination on a touch screen (which also has TTS for the entire menu, which is really well done - you have a big button on the side that you press and then it goes through all the options reading them out, and you press again to confirm) and then tells you which of the six elevators to take. When we initially got it, you used to be able to make a "group call" (i.e. have one lift go there without any additional stops), but that got locked out after students used it too much.

[@endlessoul]

Thank you for wiring up the button. Satisfying to see the press illuminate it.

[@gordonborsboom7460]

Had to take the stair the other day while changing out a 5 HP VFD driven motor on a rooftop. The Thyssen Krupp elevator tech was trying to fix a malfunctioning key pad. It is amazing how much electronics is in a modern elevator. Thanks for the diversity Clive.

[@jtveg]

One takes for granted the incredible amount of complexity required for conditioning and addressing a simple push button switch. Thanks for sharing. 😉👌🏻

[@UhrwerkKlockwerx]

I’d love to see more videos regarding elevator control equipment. I actually am a former elevator enthusiast and can say that it is super fascinating, especially the older electromechanical relay control panels!

[@matthewmoore2839]

As a hobby that must have its ups and downs.

[@Mark1024MAK]

@@matthewmoore2839 - groan 😂

[@vlfreak]

@@matthewmoore2839 it could open doors at other levels tho 🤔

[@sarah1390]

I have for a while now watched the Mr Matt and Mr Chay channel and they specialize in Old Electromechanical elevators and they also rescue old elevator equipment from the Skip for exploration.

[@andarthome142]

What's this video kzbin.info/www/bejne/aZvCZ3ulr8aZo6M

[@jimsvideos7201]

You pushed the button at the start and the elevator still hadn't shown up nearly 13 minutes later. I guess you'll have to take the stairs.

[@R.Daneel]

You leave the stairs where they are! They'll need them if the elevator is broken.

[@throttlebottle5906]

@@R.Daneel bah-dah-dum-tis, drum roll

[@blackness010]

I work as a elevator tech. It uses dip switch for address, every floor has a specific address which you change with dip switch . It can do more than buttons. And it is still use in Otis with newer system. Awesome system. Kone uses similar system for buttons.

[@Supergamer-tx9qf]

I have a Otis series 5 elevator panel I got from eBay, any idea how I can wire the position indicator to display numbers?

[@tonysever9217]

Clive you would not believe how complex the hydraulic units are. imbedded units , ive worked on the programmable motor starter units from the 2000s. ive changed fields now . still love electronics , thanks brother. WE are all brothers in electronics. thanks.

[@experimentalcyborg]

> WE are all brothers in electronics Until you have to fix the previous guy's mess of course 😂

[@JoeyClacton]

I can’t be the first to write this… But I love that Otis have a headquarters in Reading. EVERY TIME I see that in an elevator I start singing.. Sitting On The Dock Of The Bay.

[@davemugridge]

It looks like the serial interface is described in US Patent 4622551. The LM393 corresponds to the dual comparator shown in the patent. (Apologies if this is a duplicate, but I posted this information earlier & it didn't appear).

[@fazergazer]

We still use OTIS elevators in my building. At least 40 YO and going strong, of course with required maintenance! Would love to see the other bits reverse engineered. Highly enjoyable as always!

[@patrickjmorgan]

If they are 40 years old, then they wont be this typoe of s**t. i started working for Otis as an apprentice in 1972. The stuff they installed then could be replaced or maintained by any company. This latest stuff cant.

[@Kae6502]

When I worked in maintenance many years ago, I got called to a two story building who's second story call button wasn't always working. Suspecting bad contacts in the switch, I took it apart and found an unused set of N/O contacts. I switched the leads to them and it worked just fine! Having a bit of fun, I installed the Down button upside down and anounced that I just added a third story to their building! But, after having it pointed out that people would now have to take the stairs down to ground level, I destroyed my imaginary "third floor" and installed the switch the right way around. :D

[@neontime]

You were right first time about the QG transistor.. It is an NPN bipolar with integral base resistors. Type is RN1427.

[@PAINC4K3]

I also work for Otis and the thought of sending you some PCB's crossed my mind quite a few times, figured it wouldnt be interesting enough tho. Guess i was wrong lol.

[@bigclivedotcom]

Some of the lift stuff is quite interesting. A good example of industrial control circuitry.

[@jasonkuehl639]

An interesting bit of circuitry! My initial thought was wondering if there was some way I could put this to use, but then I figured the circuitry is probably specialized to the point that unless I had an elevator, there isn't. Very neat use of switching to 0v to turn the led on to note the call is accepted, though, I may be able to use that bit in an upcoming project!

[@alexanderkupke920]

Also that board is already an older design. These days with certain microcontroller modules readily available, you could do similar things with those as well, likely a lot cheaper and flexible. Those things are designed to be somewhat robust and fail in a mode that does not cause the elevator to get stuck closed.

[@0miker0]

So much protection everywhere on this circuit and very thought out. You can tell it was designed to not fail for a long as possible.

[@Black3ternity]

Uh I really dig this stuff. Not an electrician, nor technician. Work in IT. But this stuff fascinates me and is it's really interesting to see how these industrial applications differ from the regular mainstream-stuff you can buy for your home. I appreciate the insight and if you have more of this or thinking of doing more, I am happy to watch it. I would be interested in a "deepdive" from you into various industrial systems that we "normies" would never see :-)

[@Alacritous]

Otis is an old monolithic company that would use proprietary and obfuscated protocols and hardware to prevent secondary markets from forming around their products and prevent unlicensed mainentence from happening. Same as the auto manufacturers and farm equipment manufacturers. Someone is going to make money servicing that equipment and by God it's going to be them.

[@almostanengineer]

In the case of an elevator or escalator, I would hope it would be them

[@almostanengineer]

I don’t think it’s possible to be older than Otis in the Elevator market 🤔

[@ke6gwf]

I used to take care of the equipment in a large old industrial laundry, and the Milnor washing machines were made this way. Everything from bearings the size of your car rims, valves, motors, relays and contractors in the relay logic control system, etc, was custom made and generally only available through them. Relays would have multiple stacked contacts on them, requiring 3 or 4 cludged relays to replace it if you didn't have the OEM one. I loved the machines, they were very well built, because they wanted you buying their parts for many years! Lol

[@mortenhattesen]

@@almostanengineer in the aircraft industry, third party maintenance is the norm. They obviously have to be certified for the aircraft type and conform to standards and regulations. No reason not to allow the same for elevators.

[@snakezdewiggle6084]

Back side reminds me of a keyboard pcb. Of course multi layer + high current = built in obsolescence. You don't see large 317's and uC on the same board very often. Thanks Clive, that was educational.

[@analogMensch]

The 0V line on the button connections is used for touch buttons with no mechanical switch inside. There are also some duo colored buttons on the market, so the button will be lit all time and change color when it is pushed. For the special buttons like emergency call I'm not sure if the LED circuit if driven all the time or if they just use the 0V terminal.

[@millomweb]

Dad's approach to towns is to park in the multi-storey car park and park on the top level - yes even if it was a split level car park, he'd go up that last 'half' level. Next, after all getting out of the car, we'd walk the periphery of the top level and admire the views ! It was no different in Blackpool. Having done this there, we walk to the lift and pressed the button. The lift never came. We eventually walked down a level and managed to use the lift from there. On returning to the car in the evening, yes, the lift wouldn't take us to the top floor. So we had to walk up the last flight of stairs. On passing the lift to get to the car, I stopped - and pushed the landing doors open ! Yes, they weren't locked ! I guess the lift had a lock problem on the top floor and they'd disabled calls to that floor. This I guess was back in the 1980s.

[@omegaofmankind693]

I worked for Dupar there competition, the floor switches we commonly use are just a i/o mechanical switches all the logic is done in the elevator control module.

[@ian-c.01]

It makes me smile to hear you saying 'lift controller' because I know that will probably confuse some people across the pond ! I sit through a lot of videos made by people who are constantly misusing English words and I am constantly translating in my head words like 'shop' for 'workshop' and 'side' for 'end' ! It amazes me in this time of international internet that so many people have such a poor grasp of the language they use daily and don't even care, I mean why do they call it a 'hot water heater' instead of 'water heater' ? I wish there could be a standard English language that was taught wherever they speak English.

[@ke6gwf]

I wish everyone in the world would speak English and stop learning their own languages! /s ;) When you consider that there are many types of heaters, "heater, hot water" makes a little more sense. It is the heater that produces the hot water, as opposed to the heater that heats the air, or thaws out the ice etc.

[@ASlutty9SUnit]

This sounds like it's meant to be derisive against American English, or people who don't understand their own form of English, but I can't tell which.

[@whitesapphire5865]

There was a time when all English speaking countries spoke "English" English, but, and especially the USA (before it became United), as these countries strove for independence from Britain they electively changed the language they used, to make it a unique version of their own. The sad reality is that the original English is now being eradicated, courtesy of the internet, Microsoft and Apple, et al. and supplanted by US English. "Old" English will cease to be by the second half of this century.

[@ASlutty9SUnit]

@@whitesapphire5865 ​ "Original" English. I'm sorry, but Anglo-Saxon hasn't been used in over 1200 years! What in the good graces do you mean, "Original" English? Even British English is just a Nordic, French, and Latin bastardization of Anglo-Saxon! Which, in and of itself, had varied forms based on where you lived! You could probably have communication between a West Saxoner and a person from Mercia, but it'd still be akin to a British person talking to someone in Ireland! (Or someone from Australia, god save you then. THAT'S some bastardization lol.) Now I do agree that modern bastardization is not something I'm overtly happy about. But the whole "Brit-English best" thing has always sat off with me. tl;dr: English has never been static, period. You're wrong if you think so. But at least American English isn't Australian English, so we should all be happy about that.

[@ke6gwf]

@@ASlutty9SUnit the funny thing is, it's the UK English that have slaughtered the language in his example, because the guy who invented the "lift" (in the US) called it an "Elevator", so calling it a Lift is slang and not its proper name lol

[@taliakuznetsova7092]

Cause of your videos I bought a nitecore tube recently and 10/10. Charges with the same cable as my phone. Nitecore Tip SE is what I got. My old keychain touch activate light was dieing and now its fantastic. Adjustable modes, can charge in my truck while driving, long battery than the button cell, no more accidentally activating when my knee touches it. Great utility light tho not heavy enough to put in my fire gear. You do more unintentional advertising than you think. Next thing you know I'll be buying elevator parts.

[@RobertLeBlancPhoto]

Ah, the good ole RS-14 button board. There's literally millions of them out there, and whenever there's an issue with a hall button not working, it's almost always due to a damaged button, and not this board. I have literally seen hall stations driven into with vehicles or man lifts, destroying everything, and I can just change the buttons and it all works again.

[@alessi4249]

I once worked for Otis elevators, they wanted me to come up with a slogan. I thought I had a great one - Oatis elevators, they never let you down!

[@nicku33]

RIP Normie

[@casemodder89]

so as you dont even know the spelling - i guess you never worked for otis !?

[@brian_abroad]

Just for fun; How about, “Otis Elevators, where ups and downs drive our success.

[@CharlesPruden]

I believe that they use a proprietary protocol so you can't use a different manufacturers parts on its network.

[@omegaofmankind693]

If one of my clients wanted there button face we had an adapter to use them on our dupar switches. We had similar things for MAD buttons

[@orac229]

My POE gigabit switch blew up the other week. At the 52volt input (not the power supply) on the main board it has 2 bypass/decoupling capacitors that blew a hole in the circuit board, almost all the way through the board and the tracks connecting them. Huge evidence looks like water was the cause but it is not located near a source of water or moisture.

[@gregorythomas333]

When you started describing it the first thought was this resembles a CANBUS :) I would love to see a comparison with the Chinesium made one to this Otis made one.

[@Ravenor907]

Your voice is so damn soothing. Reminds me of my Welsh Grandpa. Maybe consider making audio books my friend.

[@markiangooley]

2003 on the board. I wouldn’t be surprised if they’re still using the same board in new equipment: hey, if it works well…

[@PAINC4K3]

We do still use them, and yes, they still do their Job perfectly fine ;)

[@randycarter2001]

Another reason for the 0v feed to the button. Solid state touch senors would require power. These would have no mechanical movements. Either detects the physical touch on metal or the presence of a human just above the pad.

[@Mountain-Man-3000]

Don't anger the Elavator Mafia Clive...

[@usdohs]

They do have a CAN version of this board called a cf14, for can fixture instead of remote serial. Everything Otis does is proprietary due to competition in the marketplace. Rs485/422 protocols actually are used for some things, but still in proprietary ways.

[@stewartthompson72]

For a small system this seems like overkill, but I guess in a large building with many floors and multiple Elevators, it becomes more efficient. Very interesting Clive.

[@campbellmorrison8540]

You have done well to get as far as you have, drives me crazy trying to reverse these types of boards and once you have you still have no idea what the SW is doing. Its all very clever but OMG its just too hard, really makes me wonder about the whole idea of right to repair,

[@marcelpalmen]

The data protocol was already used on Otis controllers in 1989. It was on another PCB, but they are basicaly the same.

[@jkbrown5496]

30 volts likely for an old network in an elevator shaft. I remember reading a Dick Morley (Father of the PLC) column where he mentioned they went with, either 12 or 15 volts, for the network comes on the original restaurant ordering registers his team developed due to the noise the line picked up running through a restaurant.

[@matthewmaca6675]

Deviant Olam has some great talks about elevators

[@martinlouden9005]

I feel elevated Clive, you must have pressed my buttons!

[@johndododoe1411]

Having designed my own protocols for circuits, I wonder if the OTIS protocol includes error correcting codes to ensure noise cannot change or block commands. After all, this is safety critical machinery, and nobody wants the STOP, ALARM or OPEN buttons to get lost or added by trivial faults.

[@dickcheney6]

Buttons that are safety critical probably would have separate lines.

[@livingdeadbtu]

Most networked devices are something like this.... Button at address 7 pressed ACK (host) If it didn't work Button at address 7 pressed Nothing (no response from destination) timeout on random counter button at address 7 pressed NAK (host) - (Was seen but garbled, not understood due to stomp traffic) timeout on random counter Button at address 7 pressed ACK (host)

[@mumbaiverve2307]

Very interesting video ! I have seen some cheap fire panels which use serial communication for connecting various nodes ( smoke detector, glass switches, etc. ) They were running a UART Rx/Tx with an optocoupler to switch 24V to get distance. The baud rate was less than 9600 IIRC. There was a master/slave protocol, with the main board pinging each node and waiting for a reply. Otis make large revenues on their AMC , so i guess it makes sense for then to use proprietary protocols. Also AFAIK CAN bus needs to set unique priorities for each node, and it may not make sense here because each floor switch would need the same priority; (maybe someone can correct me on this) Would be interesting to see if BC makes a follow up video on this.

[@R.Daneel]

I think I heard someplace that Otis used neon indicators that didn't light up BECAUSE you pressed the button, putting your finger near the neon caused it to strike, and the circuit saw THAT as a button press. No moving parts. (boy... was it "The Acme School of Stuff"? A fantastic Canadian science show from the 80's. Definitely worth a search for that. You'll love it in the first 2 minutes).

[@bigclivedotcom]

The Otis touch buttons. They were powered by a DC voltage just below the strike threshold of the neon, with ground referenced AC superimposed on it. When you touched the surface you provided a capacitive coupling for the AC that triggered the neon, and it then latched a series relay.

[@tze-ven]

That SOT23 with QG marking code might probably be RN1427. It is a NPN transistor with built-in bias resistors.

[@brian9731]

RS485 or some variety of it is used in all sorts of security applications like alarms, access control etc and also for fire alarm datalines. You could use IP but that would then tend to depend on someone else's infrastructure for their operation. For safety in lifts and for security and safety in access control systems that kind of dependency is not good.

[@scratchdog2216]

My G'Pa was an Otis installer then inspector for years after WW2.

[@channelundefined9735]

I have a newer revision of this board, stamped 2014. It appears that they changed some of the layout and replaced the main chip with a different model. The data connections are now labelled "CAN H" and "CAN L". The main chip has also been replaced with an Atmel 90CAN32 which has a CAN controller. Maybe Otis recently transitioned to CAN based modules. This would possibly make it easier to send our own data to these modules and control them.

[@Tocsin-Bang]

In the early days of the council tax, one local authority tried to collect from a Mr Otis Elevator. Someone spotted the name on a door in a block of flats.

[@whitesapphire5865]

Oh, I so much want to believe that to be true! It would be so typical of local authority bureaucracy. I suppose Mr Plant Room also failed to pay his council tax.

[@jensschroder8214]

The LM393 has OC outputs. Maybe an I2C protocol? This would require pullups somewhere. But then there is no short circuit when Hgh and Low are on the bus at the same time. High can be higher than 5 volts.

[@gavincurtis]

In San Francisco, the conformal coating on the elevator circuit boards protects against urine.

[@db-iu7fz]

I’d buy that for a dollar

[@Nono-hk3is]

Thank you Clive. What's the voltage on the LED pin? Does the LED pin drive the LED or just switch it on?

[@bigclivedotcom]

The led pin switches to zero volts. The 24V is always present on the led positive connection.

[@pineappleroad]

I remember that when i was at college someone kicked the ground floor and second floor call button panels (the first floor, third floor, fourth floor, and fifth floor panels did not get kicked and so continued to work normally) On the ground floor the button got misaligned, and you had to press it in a certain spot for it to work The second floor panel suffered the worst fate, the wires broke and so the panel was completely non functional, and for the rest of the college year the panel remained non functional (so when a wheelchair user needed the lift on the second floor, someone else had to go to another floor, call the lift from there, and then send it to the second floor), i left the college at the end of that college year, so i do not know if it has been fixed or replaced

[@jankcitycustoms]

I was sick once in 6th grade and puked on the sidewalk outside the building. nobody ever cleaned it up and the stain was still there my last year of high school.

[@Blackhawkso]

DeviantOllam and his elevator mate might be able the shed light on the network protocol that it uses.

[@2lefThumbs]

MOSFETS (surface mount) are often labelled with just a date code, it might be what "QG" is in your case, rather than identifying the type

[@ProtonOne11]

If they have a patent on the serial link physical layer or protocol, then you would be able to go look up that patent and see how it actually works. Connecting an oscilloscope to see if it tries to talk to another board could help as well. I'm acutally a bit surprised there are not more surge/burst/ESD protection diodes on a board like that.

[@McTroyd]

I think you're right on the money that the protocol itself is quite old, and might stem back to the days before computer controlled elevators. Since neither of us is seeing a driver on the board, I guess they're bit-banging the comm bus on the microcontroller. Maybe they're using resistor networks (like the button), and/or FETs to deal with the voltage difference. 🤷‍♂️

[@0miker0]

Not sure if you have already released or have you considered writing a book on best practices circuit design? Through the years you have reviewed really bad and really layouts and it would be good to have a book condense all of the good ideas into one book.

[@Joelsfilmer]

I second this. **Practical circuit design by and for dummies**

[@0miker0]

When I started out all I had were the hand drawn style Forrest Mims books. A great fun way to learn and it brings back nice memories.

[@mysock351C]

Looks like they like the LM317 regulator almost as much as I do...

[@misterhat5823]

It is odd that they didn't use the 78L05 for the 5V rail though.

[@davidmcgill1000]

Time to get some more PCBs to complete the network for no other reason than to say you can?

[@Sir_Uncle_Ned]

The voltages scream "Electromechanical" and I have little doubt it is, indeed, for backward compatibility with older systems. The proprietary elevator control network system makes sense because you need to get a system that works reliably as possible in a wide variety of conditions and installations while also maintaining backward compatibility. Something like CAN bus would be a good choice if you were engineering the system today, but the fact is that the systems being supported here date back to the early 1970s where there was no such thing as a computer small enough to fit in a car that wouldn't cost more than said car itself, and even if there was, it was by itself with no need to communicate with another computer. CAN bus would not be a thing until 1986 by which time the modern operatorless elevator was well established.

[@johnsenchak1428]

Got to love the Dio-Deees

[@kenjewell3889]

Is it using MODBUS RTU? I designed a 2 channel i/o Modbus board for an American elevator company many years ago now. The idea was to save cost.

[@4lecsg]

this is some hardcore stuff, I'm impressed

[@d.t.4523]

So that's why I had to take the stairs. Clive stole the button controller. 👍😃

[@UpLateGeek]

I'm guessing the reason for the proprietary network was for vendor lock-in. If third manufacturers can't just buy an off-the-shelf transceiver and throw a comms protocol library at a generic microcontroller, it's going to make it a lot more difficult for your customers to source cheaper third-party parts that work with their elevators. And if they've got a patent on the protocol, they can just sue anyone who tries to spin their own clones.

[@miles_thomas]

I wonder if the network protocol is some variant of I2C/IIC (it's old enough as a protocol, and has the right sort of capabilities and properties, developed for internal network for TVs to carry the remote control button presses from prebuilt remote control receiver ICs, later used for allowing computers to interrogate the attached screen.)

[@kimchristensen2175]

The "MosFET" marked QG could actually be a Toshiba RN1427 which is a bipolar transistor with built in base resistors. So your original hunch could have been correct.

[@mrfrenzy.]

It would be easy to desolder the component and test it.

[@rexsceleratorum1632]

Technically it is not a transistor but an IC

[@kimchristensen2175]

@@rexsceleratorum1632 yes... Albeit a very simple one.

[@f.hababorbitz]

The reason for switching a positive signal on a switch is when you analyze this in a fault analysis, the probability of having a signal fault to ground is much higher then faulting to a voltage. This I learned from working on avionics. They protect against transients, as again, a fault analysis will always fault the device in the worst case outcome, as you don't know what the internals of the micro processor are, so put in overkill protection to minimize this fault possibility. Also, I was on a working group looking for a new serial bus, we tested CAN bus, the signal levels are too small, and would be upset very easy with RF radiated and conducted susceptibility tests. I don't think they use drive by wire in cars, using the CAN bus.

[@DerMarkus1982]

Clive: " ... 'cause I've already blown it up ..." My brain : "Yeah, thing's going boom! Show me, Clive! ... Oh."

[@ESCcrasci]

Elevators are becoming smarter by the year. I can't imagine an elevator that will have a Bose sound system with Google/apple assistants built-in. :)

[@greenmanreddog]

It may be that the capacitor on the switch input to the MCU is being used as a switch debounce.

[@alexlo7708]

I think PIC MCU was used as memory for how many button that being active pushed and memory of what floor number the lift was being.

[@plonkster]

PIC MCUs often have built in RS485 hardware.

[@plonkster]

@Arpad Toth Now that you mention it, I think I may in fact be confused and my original comment would therefore be wrong. Of course any chip with a TTL-level UART port can be married to the relevant line-driver and that would turn it into a proper RS232 or RS485 port. So I may be completely mistaken here. I didn't see such a transceiver chip on the board, and I'm not sure if there is a PIC controller with this built in (probably not if google serves). Some of the ARM Cortex SOCs I've seen even have a built-in CAN-controller, and you just have to add a CAN transceiver (eg MCP2551 or TI ISO1050) to finish the job.

[@d00dEEE]

How widely adopted was CAN in industrial control circa 2003? I worked with lots of automotive stuff in that era, and CAN was just becoming The Big Thing, so I would not be surprised by non-CAN car/truck boards with early-2000s copyright stamps.

[@johnsenchak1428]

The MCU maybe works like the IRQ interrupts in a Intel CPU, where it controls hardware calls for process time

[@johndododoe1411]

Nope, all that is configured on the central computer in the engine room. This is like an RGB Gaming keyboard, except only 4 keys and one color for each.

[@fonkbadonk5370]

We have been asked for a quote on a control system for a hospital elevator system recently, that is nearing the 20 year old mark by now. From the schematics we had been given, it looked like all buttons, light and numerical indicators ended up as simple discrete signals from the POV of a global controller. Including the button and level indicators for each cabin. If I recall correctly, this wasn't an Otis system to begin with, and this honestly looks horribly overcomplicated for the time. By 2003, most elevators, at least in a slightly commercial setting, would probably have used some sort of PLC overseeing the whole operation, that combined with any kind of bus would have easily coped with all inputs and indication needs. The only setting where I could imagine this kind of module making sense would be for small residential use, like 8 stories, maybe 2-4 shafts at maximum. But even then, getting all the special-operation modes across (fires or other kinds of failure) seems troublesome to me, given how little an even half-decent heading PLC would cost compared to the whole setup. Especially compared to custom made silicon and PCBs. Therefore this really does somewhat look like the attempt of some 70/80s engineers/electricians trying to force their way into the 2000s while not really keeping up with times. Am I horribly blinded here?

[@bigclivedotcom]

It's possible it may have been a retrofit controller for a traditional hard wired system. More work to physically install, but simple and often very reliable.

[@fonkbadonk5370]

@@bigclivedotcom All three are actually good arguments. And indeed, handling locally what you can does have its benefits at times. Thanks for the reply!

[@twocvbloke]

I'd hazard a guess that they created a proprietary interface so that people working on their lifts couldn't bodge in parts from other manufacturers that used Canbus or RS485, so had to buy the original parts from Otis at their set prices, just a guess... :P

[@mortenhattesen]

It would be really interesting to see the schematic for the network driver 😉

[@lImbus924]

You definitely need an X-Ray cabinet :)

[@TheBauwssss]

@@manitoba-op4jx ? I must honestly admit I *am* _really_ curious how you're actually planning on utilizing the hydraulic press to x-ray the PCB? I do suppose you're suggesting we use the press for some other purpose rather than just using it to violently crush the PCB with the (likely very entertaining) application of some brute force? My apologies if my English isn't up to snuff right now, it is very late and I am really knikkebolling fcking hard, like a tired human or something, so I gotta go and take a huge fuckin' dump, brb! Thanks for reading my amalgamation of random English words (and a few other foreign ones too!) 😋👍😀🤗☺️ 🤣

[@health101DOTorg]

Would you do a for-a-fee consult? I have a simple IC555 timer circuit that controls an intermittent windshield wiper controller, and I need help in identifying which component controls the initial (power-on) pulse to its relay (it's too long compared to all the delay pulses that follow that are controlled by the potentiometer). Thanks!

[@assassinlexx1993]

Very clever but where is the control board that senses someone pissing in the elevator and the floor opens up. To send the b****** to the bottom.

[@FennecTECH]

If I recall these use a canbus network

[@carlosgarcialalicata]

What type of connectors does it use for wire-to-pcb? That is always the most problematic part of my PCBs

[@TekedixXx]

Love it! but everyone knows Dover Impulse are the best elevator switches.

[@markussommer1950]

Interesting I thought CAN or a RS485 Bus was quite a standard. Competitors use CAN for over 20 years.

[@erbenton07]

Where is the part that makes you wait forever before the doors close after you press the button?

[@bhupiistersingh4097]

Is it possible to reverse engineer it? Did any of you guys tried reverse engineering the RSL protocol?

[@andrewmain3572]

Hmmm, the first video of yours I watched was about a lift controller, a clunky elecro-mechanical gadget fixed to a big piece of slate.

[@krnlg]

That was one of the first of Clive's videos I saw too. Must be a memorable one, slate circuitboard!

[@mtreis86]

I have an idea for reverse engineering multilayer boards. If you had a small (microwave) phased array antenna receiver, and you sat the board right on top of it, I bet you could inject signals with a probe and identify the paths they take. Effectively turn each circuit trace into an antenna while it is probed. Complex but would it work? Boards that are microstrip may not but I am not sure. Once you're well above the frequency the board is designed for then everything starts coupling.

[@weerobot]

John McClane "Oh No elevators.." lol

[@dickcheney6]

Because of the Die Hard movies, when another movie or game depicts someone climbing out the top, I like to say they used the "die hard hatch"

[@mad_circuits]

The circuit looks a bit overengineered and complicated. It has to detect 4 button presses and control some data lines, right? Is it all about overvoltage and vandalism protection?

[@bigclivedotcom]

It's about extreme electrical environments, including customers walking across carpets and discharging static electricity to button metalwork.

[@markfergerson2145]

It's also about safety (reliability specifically) and security. Modern elevator systems need lockouts and what amount to passes to control who has access to which floors. The first concern means the board looks overengineered, but it's as Clive says to cope with accidental overvoltage events as well as making sure it fails "safe". There's also "debouncing" the signal from the physical button signal to the microprocessor- that's another function of the cap/resistor/diode network on the MCU inputs. The input pins typically go to an internal RS or other flip flop. (A quick video on debouncing seems called for, hint hint) The second concern is mostly handled by an external security system (look up Otis Compass) that examines requests from boards such as Clive showed us and then either allows or forbids the doors to open or the car to move.

[@mad_circuits]

@@bigclivedotcom Thank you for the answer. Wouldn‘t it be more cost efficient to use a tight full metal enclosure for the circuit board (faraday cage) and secure the switch lines with one suppression diode (TVS), each side. In addition, use a good switch metalworks isolation… ? I‘m wondering if making the circuit more complex is a good solution. Also: is using a custom chip part really a good idea? It would have been cheaper and more future proof to use e.g. a standard (one-time programmable) PIC16, there is also a read protection feature to save intellectual property.

[@Mark1024MAK]

@@mad_circuits - the chip may well be a “standard” microcontroller, but made using a mask ROM. Hence the manufacturer has used the customers part number. This is cheaper if ordered in the tens of thousands.

[@rj7855]

@@mad_circuits a metal enclosure doesn't help for suppression of electrical spikes/noise coming through the in and output wires.

[@andrewedis9907]

I'd like to see more elevator equipment and thankyou for wiring up the button it made me smile 😊

[@chilllytube]

Would there be clues about the networking in Otis’s patent?

[@stanleyknight8173]

It is only a dumb question if you don't ask. So I don't know. How many floors do you think this controller would work 4 or more. Could it work work having 4 contacts 8, 16, 32, 64 or more?

[@bigclivedotcom]

I'm not sure how many nodes the network can address. Above the limit they might use another universe (complete separate network).