So I am fabricating a dumbwaiter and I need a control system. I am using a 200kg winch to power the lift. The winch comes with an upper limit switch and a wired up/down/stop controller.
I will need to install 2 lower limit switches and 1 additional upper limit switch. I purchased 2 wall mountable push button switches that have up/down/stop buttons and I also got some magnetic switches to stop the motor in case the shaft doors are open.
I need to wire the push button switches so that if a person upstairs is pushing the up button and someone downstairs is pushing the down button only one will work at a time.

The motor is very slow and the travel distance is only about 3 meters (counter height 1st floor to counter height 2nd floor). The lift will only be used for plates of food and not for sacks of flour so I don't need an overweight sensor.

Should I go with an arduino or should I go with relay logic? I am a home electrician so I have no problem working with 220v single and 3 phase. I am not skilled with circuits and small electronics but I have made some very basic kit circuits recently and this is a great opportunity for me to learn more. Could anyone provide me with a diagram on how this could be done?

Much Thanks

 

Here's a simple relay interlock circuit that should do what you want.
If either of the Up or Down buttons is pressed, then the opposite direction buttons are inhibited.
The relays can also be SPDT as desired.

You could also use discrete logic circuits or a micro processor for this purpose but that's probably overkill (although those approaches may be somewhat cheaper).

 

Mucho kudos to you Crutschow. Problem is the only circuits I have made are an led and a parrot sound push button which came from a kit. I actually mapped the circuit out on a bread board instead of using the circuit board in the kit so I could try to understand it better. I still have a lot of learning to do and unfortunately I need to install this in about a weeks time. So I am thinking of having someone build it for me with relays.

If its possible I would like to build it myself but I would need more to understand it from a perspective. Do you think it would be easier for me to do this with an arduino or with relays since I am completely knew to both.

 

Do you think it would be easier for me to do this with an arduino or with relays since I am completely knew to both.

The learning curve for a relay is about 10 minutes.
From scratch, the learning curve for an arduino is probably a few weeks to a few months (or more).
So take your pick.

 

There is also a Smart Relay if you are at all familiar with PLC logic.
Max.

 

Here is a circuit that I think will work.
When you push the UP button, relay 1 operates and its 1A contact holds it on and removes power from the relay2 (DN) circuit.
The UP relay will stay on until the UP Limit switch is opened by the elevator hitting it.
Similarly, for DN.
So only one way can be used at a time to avoid confusing the poor elevator
The extra contacts are wired to suit the motor and that will depend on what it is.
Of course, the relays could be mains AC ones,so remove the back EMF diodes and run between Active and Neutral if that is the case.

It could be fancied up with indicator lamps across the relays. Also, an UP and a DN push button would be fitted at both floors. I only showed one of each.

 

Hi

Any circuit safety requirements for dumbwaiter controller? Door cutoff switches? Fuses? Maintenance?
If so, recommend using relay based circuits as much as possible.

eT

 

Thanks tp everyone for all the replies. I have seen some really cool videos about interlocking circuits i don't have any idea how to set one up yet.

and

. If anyone knows of a video which breaks down how they work and how to wire one please post the link.

I'm not able to find the meaning of all the symbols posted by crutschow yet. dendads diagram is a bit hard to read but I recall most of the symbols so I will just try to work out how to wire this one up.

But I was thinking about dendads comments and recalled this video about latching relays in an old lift. And I was thinking couldn't the relay just switch between 2 circuits so that opening one would close the other. and the limit switch would break the latch. Or maybe thats what dendad meant? Also anyone have a brand or a type of relay that could do this so when I go to the electronics store I could show them. (BTW I live in a third world country so most things are not going to translate very well to local language.

 

No Safety requirements. I will make door cutoff switches. But I have worked on a professionally built dumb waiter and they seem to break down every week because of the door cutoff switches. This lift is a very short height and the load is very light weight.

 

It may help to draw the schematic up in standard ladder style format, once you gets used to it it makes circuits easier to follow.
Here is a useful aid. p6 on.
Max.

 

Thanks that helps a lot with symbols. I think these two videos will have everything i need to know. Just need to study them.

anyone know what that chip is on the bread board on the first video? And in the other video; Is it just standard relays wired in a certain way to make them interlock? If not is there a special type of relay used?

I am using just a single phase winch for this lift.

 

Just had another thought... if a relay can operate 2 switches it could open a normally closed switch on the circuit for the button I didn't press and it could close the circuit on the button I pressed. That must be what crutschow meant and what the second video is. seems simple

I'm guessing a double switch relay allows you to set eachswitch as normally closed or open.

 

Exclusive OR should do it for one.
There are a few ways.
Max..

 

Just had another thought... if a relay can operate 2 switches it could open a normally closed switch on the circuit for the button I didn't press and it could close the circuit on the button I pressed. .

There are a few relay/P.B. interlock circuits in the PDF, starting with p6 onward.
They can be adapted for your use.
Max.

 

I did not read all the posts, but my idea is that the button will be pressed once, unless it's a double pole, double throw slide switch.

Of the button really is pressed 1, I suggest a 1 shot timer 555 which will keep the lower circuit inactive, while the upper one is active by a simple transistor.

The idea is to put a transistor, which will ground the lower circuit, while the one shot timer is active.

This can be made even simpler. The upper button can set a trigger (t trigger), while the lower button will reset it. You can connect the 2 outputs of the trigger to the upper and lower circuit, so 1 will always be off.

In order for the buttons to not work, until the lift reaches up or down, there must be a switch activating when the lift reaches up and a switch activating when the lift reaches down. Also it will require a timer 555 to delay the buttons being turned on for a few seconds until the person opens the door.

 

Arakel, I think everything I need can be done with relays. Thanks for drawing up the diagram. If the 55 is actually working on a timer I'm concerned it wouldn't be accurate.

I'll go over your diagram later. If everything can be done with relays I'd rather go ahead with it since I'm kind of understanding how the relays can do this and adding transistors in may add complication and my deadline is in a few days.

 

You can do it however you want to. But you should keep in mind the defences, like a few seconds of the lower circuit not working, while the upper door is opened and closed and the opposite. Also the lower door can not be opened until the lift reaches down and the opposite, or someone might loose his hands.

The timer will be accurate depending on the components used, nothing is perfect though. The accuracy here is not really important, because it will be a one shot timer. Whether its 10sec for the door to open or 10.5 sec, no matter.

 

See if you can organize a mechanical lock so the doors can only be opened if the lift is there. Cover it with a screwed down access plate that can be removed if need be to fix faults.
And if you add a switch on each door, have both in series, and if a door is open, all the power if disconnected.
A key operated master switch is often a good idea so it can be locked out.

 

See if you can organize a mechanical lock so the doors can only be opened if the lift is there. Cover it with a screwed down access plate that can be removed if need be to fix faults.
And if you add a switch on each door, have both in series, and if a door is open, all the power if disconnected.
A key operated master switch is often a good idea so it can be locked out.

I was thinking of a deviator key or the same principle.

 

So I took the schematic from Crutschow to a control supply shop and I talk to the head control maker. He said really fast in a foreign language that it wouldn't work for several reasons all of which I couldn't translate fast enough while talking with him. He also mentioned that there was no need to worry about someone pressing the down button while someone was pressing the up button as the motor will run in the direction pressed until a limit switch is triggered. I'm guessing this is by use of a latching relay?? I was planning to buy the equipment and wire it up my self but he said they could produce it for about 150 US in 3 days. So knowing I had a schematic that may not work and a week to complete this one I decided to let them produce it and I would try to learn from the control they provide.

So I'm posting pics and please detail what each item is and what it does.

Also he need to remove a white cylinder from the old control which came with my winch and reuse it in the control box.