Here's the 'resettable' version, with 'power out' safety relay. After a power outage the AC remains isolated until 'Reset' is pressed, restoring AC power and signalling to send the car to Level 0 (unless it's already there).

View attachment 365520

If I'm following this correctly, the AC Power is dead unless the reset switch is pressed as it's run NO thru the reset relay and there is nothing that triggers that relay except the reset switch, without the switch pressed the motor has no AC.

Also when pressed, you're triggering the down relay? But only if the level_0_limit_NC is not tripped, in which case it does nothing.

Also the +12v contacts create a loop back into itself thru the switch.

Essentially, holding reset, motor gets power, trigger down relay, car moves down, hits the bottom, limit switch interrupts voltage to relay coil and shuts off relay. Let go of reset and motor loses all power, and nothing does anything.

Unless I'm completely off here.

Either way I'd scrap the whole emergency reset aspect as it's not needed. On power loss the command relays will de-energize and the car will just sit where it is, you can then just push the call button to put it in motion again.

I'll have to study the NC/NO limit switches a little more, at first glance it looks like that unless the car is fully at level 0 or 1 then the buttons are essentially dead. Of course this is mainly a problem with the power loss case.

 

i saw that...

for operation with two buttons (op/down) or three buttons (up/down/stop) circuit is very simple, which is what i posted in #32.
irving went through hassle of making it work with single button but at a cost of additional limit switches.

personally i find illustrative representation of circuits difficult to follow, but that is probably easier for people who rely on shapes of parts rather than function.

i prefer relay logic in relay ladder form - one can read it (and sound it out) directly as a set of instructions. also reading that is simple, using conventional form (left to right, and top to bottom) while using only three symbols (coil and NO and NC contacts).

the version using depictions may look easier to follow for someone only looking to reproduce it - without understanding what it does. but with wires looping around and in every direction (like maze - up, down, left, right and then again...) this is harder to read.

for example, one could literally say it over the phone:

"if PB1 is on or K1 is on, and not LS1, and not K2 then turn on K1"
or if substituting with text labels
"if button UP is pressed OR relay up is already on, AND NOT upper limit switch is reached, and not relay down is on, activate relay UP"

and listener on the other side would be easily able to sketch the circuit in real time.

that is not so easy using other representations (like what TS started with, and others adopted).

btw. if using single button per level is a must, this can be done with just relays, without additional limit switches. this makes things easier for manufacturing (complex part is pre-fabed in a form of a small enclosure with relays), this is also simpler for installation (no need to instal, setup additional switches, run cables, etc).

for simplest wiring inside the box one can use smart relay (tiny PLC) like Zelio, Logo, or whatever. logic is the same but transferred like program.

anyway, to me it looked like TS was happy with replies.

 

Essentially, holding reset, motor gets power, trigger down relay, car moves down, hits the bottom, limit switch interrupts voltage to relay coil and shuts off relay. Let go of reset and motor loses all power, and nothing does anything.

Nearly, once reset is pressed that relay holds itself on, so releasing reset continues with power to motor.

I'll have to study the NC/NO limit switches a little more, at first glance it looks like that unless the car is fully at level 0 or 1 then the buttons are essentially dead. Of course this is mainly a problem with the power loss case.

If car is between stations neither call button works so the only way to get the car moving is to bypass the NO contact of the Level 1 limit switch while pressing a call button.

Therefore a simpler reset arrangement is a reset button from 12v to the junction of the limit switches on the DOWN relay.

It's generally good practice to disable power to a motor if it was running though in this case the interlock does that so the reset relay is arguably overkill.

 

I have a feeling all these designs will not work with the geared winch you have.

Most of these designs are for a 120v motor which has a Hot and a Neutral, 220v is different as it has 2 hots, L1 & L2, as well as possibly a Neutral as well.

The elift schematic is for a 3 phase design with a motor controller do the dirty work of spinning the motor in the desired direction.

Do you have a link to the winch motor or the instructions on how to hook it up? I believe you mentioned it has 3 wires? If it's 3 wires the L1 would most likely goto a common wire, with L2 going to one of the other 2 depending on what direction you want it to spin. You don't want to treat L1 as you would a Neutral and leave it connected at all times as that would leave the other 2 wires hot at all times with 120v.

Overall what's really complicating the setup is the 1 single call button requirement. 2 buttons one for up and one for down, or even a 3 position momentary toggle switch where it naturally resets in the middle would solve most of the complexity.

 

Do you have a link to the winch motor or the instructions on how to hook it up? I believe you mentioned it has 3 wires? If it's 3 wires the L1 would most likely goto a common wire, with L2 going to one of the other 2 depending on what direction you want it to spin. You don't want to treat L1 as you would a Neutral and leave it connected at all times as that would leave the other 2 wires hot at all times with 120v

All the other designs I've seen either use a 3-pole relay and switch both N and either L1 or L2, or, as you suggest, drive a 2-pole contactor for each direction switching both sides of the motor. Obviously this is safer than switching just the one side

Overall what's really complicating the setup is the 1 single call button requirement. 2 buttons one for up and one for down, or even a 3 position momentary toggle switch where it naturally resets in the middle would solve most of the complexity.

Really, why does that complicate things? Two extra micro switches and 2 diodes is hardly complex or breaking the bank for what I consider a sensible improvement in functionality. I note the elift schematic also has extra NO limit switches driving interlocks for doors.

Personally, if I was doing this, I would have used 2 relays to switch both sides of the motor and set direction and a 14-pin DIP microcontroller to implement the logic, and avoided all the messy wiring!

 

logic can be done with small cheap general purpose relays. when multipole is needed, there are MY4N or similar (4x C form). if more contacts are needed, two relays can have their coils paralleled and you get "relay" with many contacts. this is sufficient as a building block even for very complex logic.

the actual driving of the load itself can use power relays or contactors (and those go waaay up in terms of switching capacity). those are 3-4 pole out of box but also support aux contacts (both front and side mounted). variants with reversing interlocks exist and they are known as reversing relays/contactors. this makes it possible to drive any reversible motor, of any size, in either direction.

also limit switches with 2 isolated contacts are very common (NO/NO, NO/NC, NC/NC). this makes it possible to use one contact as travel limit and still have extra contact (in same limit switch) for logic like confirmation that position is reached. this can be used for deciding if car was to go up or down when single call button is used. using slow acting limit switch instead of much faster relay contact can make even risque circuit designs smooth and chatter free (avoid race conditions).

one thing i try to avoid is waiting. one can never have enough of time and it is silly to throw it away. for me that is reason enough against single call button. if the car is not in front of me, i don't want to thing where it may be. maybe it is resting at some halfway point. using single call button one may be forced to send the car to one arbitrary direction (such as down), then press again to make it go the other way (if you are waiting at the top). this issue does not exist with two buttons, plus circuit is simpler (is is dead simple with just two relays and two NC limits swtiches)

 

I've been playing with this puzzle in my head. The conclusion I've come to is that there is no way to do this safely with just 2 DPDT relays. You need a 3rd DPDT to act as an interlock to keep from being able to energize both relays at once.

If we game out using just 2 Relays then:

You need 2 limit switches per level, one can be a simple NC, the other must be a SPST with COM, NO, & NC legs.

1 call button per level is easily solved with using an SPST limit switch, if the car is at that level, then the +12v is sent via the NO side to the relay that sends the car away, otherwise it goes through the NC side and calls the car to it, these are fed to the + side of the relay's coil.

Once a relay is activated by one of the Call Buttons, Pole 1 of the Relay you use to latch the relay on. +12v is connected to COM, when the relay is energized it is fed through NO to a 2nd limit NC switch at that level which feeds it back into that relay's coil +, when the car arrives and trips it then the relay coil de-energizes as it breaks the +12v from the coil.

This will 100% work, in the case of a power loss and the car being inbetween stops, pushing any one of the 2 buttons will call it to that button as thats the path the SPST Limit Switch is wired to send it.

There in lies the major issue, if you call the car with one button, the minute it's in motion all 4 limit switches are closed which if the other button is pressed allows the opposite button to energize the opposite relay at the same time in an attempt to call it back and latch it on.

You'll have both relay's energized and latched on and both FWD & REV leads of the motor being powered which will result in a motor that sits there humming, drawing a massive amount of current (say 5-8x the running amps), and getting very hot, very fast, oh and since it's not a dead short, the relays will probably melt before a fuse blows.

Speaking of relays, the ones the TS showed are Leone P40FC-2C-12V. They're rated for 40A resistive, since the motor is AC and therefore inductive, it needs to be derated to 40-50% or 16-20A max. Depending on inrush and how often the lift is started it could be safer to treat these relays like they're only rated for 12-15A.

 

In my example I think that it's not physically possible to energize both relays at once, assuming the limit switches are correctly positioned. The call button can only energize the relay where the NO limit switch is closed - i.e. where the car isn't. Consider the car at level 0, then the L0_NC and the L1_NO are both open, and L1_NC and L0_NO are both closed. Both relays are off. Pushing either button will send 12v to the up relay, which energises and latches on through the closed L1_NC, starting the car rising, at which point L0_NC closes, but L1_NO is still open so no power can get to the down relay. Likewise L0_NO opens, disconnecting the up relay from the push button. Now, if L1_NO is badly positioned so that it closes significantly before L1_NC opens, and a push button is being held down, then the down relay could be energised before the up relay is de-energised, which as you say, has serious consequences. However, correctly positioned switches, where the limit NC breaks before the limit NO makes, or a DPDT or NC/NO micro-switch, addresses that issue.

 

in my version i included interlock. if the relays are an actual reversing pair, they also have mechanical interlock which prevents activation of both relays at the same time. this completely prevents shoot-through conditions even if relays are manually forced.




here is video explaining how interlocks are installed.