Having problems with new lift device power control and delivery

MisterBill2

Joined Jan 23, 2018
18,477
The pendant can easily control two single pole "double throw"relays with both a normally open (N.O.) contact and a normally closed (N.C.) contact.
The motor connects to the common connection on each relay, the DC supply positive connects to both N.O. contacts, and the DC supply negative connects to both NC contacts. So one relay operating drives "raise" and the other relay operating drives in the "Lower" direction, and if both are operated nothing happens at all. This exact scheme has been suggested and used many times on this forum. The brake-resistor string is connected directly across the motor, not only assuring correct operation, but also tending to dampen any switching spikes as the motor is switched on and off.
The challenge will be in locating a source of 48 volt coil relays with adequate contact current ratings. It may be that a separate source of relay coil power will be required.
 

MisterBill2

Joined Jan 23, 2018
18,477
The scheme I proposed DEMANDS using two separate relays. No interlocking required, though, it is inherent in the design that operating both does nothing at all.
It is exactly the same scheme as has been presented for quite a few applications.
 

Thread Starter

DevineDesign

Joined Oct 22, 2023
11
I was looking at this site more in depth and was curious if other resources were available here also. Things such as sourcing, identifying parts and things of that nature.
From what I can understand the circuit will be powered from a transformer of 48vdc secondary from a 120v mains. That will then go to my pendant and also one side of both relays with power from 48vdc to other side. Then to motor. Not sure on brake resistor fully or what they even look like, how to wire.
Who needs a beer!?
 

MisterBill2

Joined Jan 23, 2018
18,477
The transformer/rectifier source was implied at the first post, I thought, given that it was not spelled out in detail. The only wiring to the pendant would be three wires to carry coil current for the two relays, which would be close to the power source, along with the resistor to drop the brake voltage. If the transformer had a second secondary winding providing 12 volts after the rectifiers, it could allow the use of standard "cube relays" that are available from many sources and are very widely used in automotive applications, all over the world. And actually, the 12 volts could be a tap on the 48 volt portion since the relay coil operation does not connect to the motor drive at all.
 

MisterBill2

Joined Jan 23, 2018
18,477
The brake resistor will dissipate as much power as the brake, because it has to drop half of the 48 volts while the brake uses the other half of the 48 volts. The relays I am suggesting are probably the most common relays around, because of their automotive application. They are available at most auto parts stores, in addition to at electrical supply shops, and many truck stops.
As an alternative to interlocking the control relays, the two buttons on the pendant could be replaced by a spring return center off switch. That would eliminate the chance of operating both relays at the same time. It might even be a cost saving.
 

Thread Starter

DevineDesign

Joined Oct 22, 2023
11
Would it be completely nuts if I found a suitable brushed DC motor controller similar to those on a e bike? Then I could achieve the battery backup/operation and maintain control of the unit without tons of extra hardware. Yes or No? I just want this to go bye-bye.
 

Thread Starter

DevineDesign

Joined Oct 22, 2023
11
I'll listen to the forum and follow your advise. I really appreciate the time that everybody's taking specially with the real novice type questions that I've been asking. How does someone put all this together on a circuit, and inside of an enclosure. Would it be smart just to go to KB and find something there?
 

Thread Starter

DevineDesign

Joined Oct 22, 2023
11
So this is the project I need to source this power unit for. This is not just a garage build or backyard project. This will and has always had an lift capacity of well over 1000lbs. So this unit can't be any different. It will have a parts list along with cab and bom file for the build. It will most likely have UL testing for certification and sold to many medical facilities world wide. So I need a solid and simple solution to be able to start production.
Lastly, my urgency with this is due to the declining status of my health. Mostly mental. I was diagnosed with early onset Alzheimer's last year. This likely will be the last team project I will be allowed to work onto. I will get a picture of the base unit in start of the build. That way there's eyes on the space and you guys can see the general idea of what this is trying to achieve. I appreciate everyone's help through this and all the good advice.Thanks.
 

Attachments

Tonyr1084

Joined Sep 24, 2015
7,899
I am assuming you also use it to put it up.
Yes. Forgot to film putting it up. Since then I've put it up and taken it down two more times. Today I'm beginning work on a built-in set of cabinets for my wife's dining room. The space is 135 inches wide so I'm not going to find cabinets that fit. She wants it wall to wall. She also wants it in Greek motif. What mama wants - - - .
 

MisterBill2

Joined Jan 23, 2018
18,477
The two bevel gears on that right angle gearmotor are not on the shaft, nor ar they mating correctly. If the gearmotor were reversed end for end then the bevel gears can be supported by the end bearings and the tooth alignment will stay correct as the load changes.. And that does not add cost to the assembly, except for the mounting holes for the gearmotor.
 
Top