Emergency Brake for an Elevator

Hi Guys
I am looking to build an "Emergency Brake System" for an Elevator (Dumb Waiter, not for people).

The Elevator has a second separate counterweight cable that I want to use as the emergency brake should the main drive motor/cable fail.

The plan
The Counterweight Cable will run over a 440mm diameter Sheave/Pulley that in normal operations rotates freely on an a axle with 10" Electric Trailer Wheel Brake Drum. The Brake operates at 0-12V DC and pulls about 4 Amps maximum.

I want to set the Arduino Uno up to measure the elevator down speed using a HC-020K Dual Speed Measurement Sensor Module. This would be set up on the above Sheave/Pulley.

With some code, this would give me a RPM of the pulley

Depending on the speed, I would like the arduino to put out a varying PWM signal

The PWM signal would go to an IBT2 (BT57960) H-Bridge to produce varying voltages to drive an electric brake drum.

For Example:
If the normal speed of the elevator is .05m/Sec the IBT2 would put out 0V
If the speed increased to .06m/Sec the IBT2 would put out 2V
If the speed increased to .08m/Sec the IBT2 would put out 3V
Etc, Etc
This would continue up to the full 12V (100% Brake Applied) if needed.

The theory is that the elevator would return to ground at a safe speed controlled by the Electric Brake.

I need your help (The Community) with the project.

Please keep you replies in simple language as I am very new to arduino programming.

This is what I am trying to achieve:
If RPM is < N (normal) - BV (brake voltage) is zero
If RPM is > N - BV = 1 Volt
If RPM is still > N - BV = 2
If RPM is still > N - BV = 3
Etc
Etc
Can I achieve this with the electrical components (HC-020K Dual Speed Measurement Sensor Module and the IBT2 (BT57960) H-Bridge) described above?

Could I get some help developing the codes required to make it work?

Thanks in advance, Fred.

What is the mass of the elevator when fully loaded?
Is this is a secondary safety feature as I believe elevators are required to have an automatic brake that prevents disaster if the cable fails?

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The usual scheme is to have spring-loaded dogs to open up and grab the frame when the cable breaks and the car is free to fall. Simple, foolproof and very effective.

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What's the application?

My advice is to run away from it as fast as you can, your liability can be horrible if it fails. To my knowledge none of the Arduinos or any of its components are rated for safety applications.

2 Likes

LEt's see if we can get you started down the correct path to build your project. The obvious first step has NOTHING to do with Arduino or electricity, but will requires some thought and fabricating work on your part. The first step is to actually mount your HC-020K and associated disk so you can begin your program development.
Please post a picture when completed.

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I think maybe the laws and regulations for dumbwaiters are a bit less legal and regulatory than the ones for elevators meant for ppl.

I say meant for ppl - raise your hand everybody who ever took a ride in a dumbwaiter, or made someone else do.

a7

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Thanks Paul, I plan to build on small scale first. Will have a small motor running at variable speed with the Arduino measuring RPM on a digital display. My knowledge level should get me that far.

After that it gets tricky :thinking:. Awaiting parts to start that first stage.

Arduino should not be used for safety critical applications .
Doesn’t the lift have built in mechanical cable break brake ?

As implied you need to consider forseeable missuse as well as potential failures .
For example the power to the Arduino fails

3 Likes

The first time I’ve ever seen both break and brake used correctly in an online forum !

3 Likes

You can do ALL and test ALL with NO motor. Just use your hand to move the device.

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Parts for stage one should be here shortly, I’ll get the taco going first and run a 5V motor via a pot to adjust RPMs

Then I’ll have a go at getting the H-Bridge to produce various voltages. Will definitely need some help there😊

I like tacos.

1 Like

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