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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 10-26-2009, 06:14 PM
shafam shafam is offline
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Default dumbwaiter control system

I am trying to build a control system for a 3 stop dumbwaiter. I would like to use latching relays and magnetic contacts for simplicity. The lift motor is a 120V reversible hoist that draws 7A. The wall switches I have are Leviton LVS-003. I need help with the circuitry design and sourcing of materials. The open door safety and the slack cable safety are in place, as is a 24V DC power supply for the relays. There are basically three circuits 1 to 2 / 2 to 1, 1 to 3 / 3 to 1, and 2 to 3 / 3 to 2 . If it were only two floors it would be quite simple. My difficulty is how to bypass the middle floor when needed. I want to stay away from electronics that because of my remote location would be unserviceable. Just simple relays and contacts. Can anyone help with a schematic and parts list. Thanks . BOB S.
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  #2  
Old 10-26-2009, 08:54 PM
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SgtWookie SgtWookie is offline
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Bob,
Are you talking about this switch:
http://www.leviton.com/OA_HTML/ibeCC...US&item=409013
The LVS-3W was the only reference I found to that on Leviton's site.

Are you in the USA, or elsewhere? It helps a great deal to know your approximate location when attempting to find suitable parts.

A motor that draws 7A @ 120V will probably draw several times that current when it's starting up. Is it a DC or AC motor?
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Old 10-27-2009, 07:57 PM
shafam shafam is offline
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Default dumbwaiter control

Yes that is the switch that i have. The motor is 120V AC. It is a geared reduction motor and an ammeter showed no extra startup amps. I'm in WV in the mountains 2 hours from anywhere, but I do get UPS and Fedex deliveries. In fact I order 80% of everything and have it deleivered. Its cheaper than a 3 or 4 hour round trip to town, and I probably won't find what I need anyway. I can put together relays, limit swithces, etc. from a schemetic, but designing the circuit is something else altogether. Thanks in advance. Bob S.
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  #4  
Old 10-27-2009, 08:16 PM
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OK, you're going to have to tell us more about the motor wiring.

Do you have the instructions on how to make the motor reversible?

Providing a wiring diagram would be very helpful. If you don't have that, the manufacturer's name and the model number of the motor could be used to find a datasheet for it.
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Old 10-28-2009, 04:48 PM
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Bob S.,

Not knowing your experience with electrical circuits I feel that I must state the obvious. Not only can 120VAC kill (and has killed) it can also burn down you house. The job you want to do is not an easy one, be careful and thorough.

An instructor I had once said, “Always assume that the person who drew this diagram up was drunk, hung over or just plain having a bad hair day and made some serious life threatening mistakes. Your life is in “YOUR” hands. Act accordingly.”

I have attached a ladder diagram, which I believe will accomplish the task at hand. I also believe that it is error free but you never know. If anyone else reading this thread sees any errors by all means... please speak out!

Do not take this ladder diagram and start wiring up your project. Take the time and make the effort to do a test mockup on a sheet of plywood using a light bulb in place of the motor. Once it is wired correctly and fully tested, then and only then begin work on the dumb waiter itself.

Not only will the mockup test the validity of the circuit but it will also give added and valuable experience.

Good Luck,

williamj
Attached Images
File Type: jpg Dumb Waiter Control 3 Floor.jpg (35.4 KB, 128 views)
File Type: jpg Dumb Waiter Control 3 Floor 120V.jpg (29.3 KB, 106 views)
File Type: jpg Dumb Waiter Control 3 Floor 24V.jpg (34.4 KB, 94 views)
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  #6  
Old 10-29-2009, 05:18 PM
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williamj williamj is offline
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Bad hair day ALERT!! Bad hair day ALERT!!

The 24V portion of diagram will not work. Apparently a relay for each floor is required. Don't know why I missed that. (bummers) Will revise...

See what I mean about mistakes on drawings and schematics?

Apologies and Mia Copas,

williamj
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Old 10-30-2009, 02:20 PM
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williamj williamj is offline
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Default revised ladder diagrams

Attached are the revised diagrams. Please check thoroughly.



williamj
Attached Images
File Type: jpg Dumb Waiter Control 3 Floor rev.jpg (37.6 KB, 257 views)
File Type: jpg Dumb Waiter Control 3 Floor 120V rev.jpg (11.4 KB, 69 views)
File Type: jpg Dumb Waiter Control 3 Floor 24V rev.jpg (41.0 KB, 85 views)
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  #8  
Old 10-30-2009, 10:17 PM
shafam shafam is offline
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Default motor info

thanks sgt...the motor is already reversible...it is a hoist motor...the type you might see lifting an engine from a car...880# capacity...16 ft +/- per min cable speed...it has a hand control that i will remove and splice my control circuit to...120v ac comes into the control and goes to two momentary contact push buttons...if you push up power goes back to the motor through one wire...if you push down power goes back to the motor through a different wire...the neutral does not come to the hand control but there is a ground wire for safety...very basic...I am very familiar with AC voltage...I wired the whole house myself...bob s.

williamj...I will print the wiring diagrams and see if I understand them...as I mentioned above, I wired the whole house myself so I understand AC and the risks...whenever possible I kill the power to a circuit before working on any wires in it...thank you very much for your time...bob s.
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  #9  
Old 10-30-2009, 10:47 PM
shafam shafam is offline
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Default 3 buttons per floor

won't it will take at least 6 ( maybe 9 ) relays???...from any floor you have two send options to the other floors, and 1 call option if the car is not on your floor...????just thinking out loud...bob s.
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Old 10-30-2009, 11:01 PM
shafam shafam is offline
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Default still thinking out loud!

and won't 2 limit swithches be required at each floor (possibly 3 on the second floor)?..one limit switch to stop travel, and one as a proximity sensor...for example...if you are on the first floor, to call the car down from upstairs you would press 1, which would activate the motor down...but if the car were already on the first floor and you pressed 1, there has to be something to prevent the motor from going down further...the same for the other floors????headache!!!thanks...bob s.
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