Load to be calculated

Hi everyone
I am being working in a project where the motor lifts the weight or aka the load, for some reasons i want to limit the lifting capacity of the motor, say if I want to lift 15kg then after 15kg it should stop. what is the best way to do this, how can i calculate current consumption of the motor so if more load abnormal current consumption or is there any easier implementation

Thanks in advance

Mount the motor on a load cell or put a load cell in the lifting line to directly measure the mass would, I think, be the most reliable.

I thought for different load different current right i dont want to mease the load in the motor i just wanna to put a limit to it so it can be same ie if current above this is consumed stop the process and give alert kinda like that

Most current is drawn whenever the motor starts spinning up. If you think that current monitoring will be enough for your project, try and find out yourself.

So you're trying to measure current, not weight?

A circuit breaker may be the solution...

Current measurement is a little "tricky", but there are a couple of ways to do it, depending on the current. A hall-effect current sensor is often the best solution, and it's generally easier to measure high current than low current.

Then you just need a relay or MOSFET to switch-off the power when there is excess current. (With the Arduino and an if-statement in your software.)

Also motors have high(er) start-up current so you'll have to do some experiments and you may want to ignore the current readings for the first second or so after starting the motor. You'd get a similar current spike if you add a load to an already-running motor. (It takes more energy to accelerate a mass than to lift it or to keep it in continuous motion.)

A circuit breaker has a little "natural" delay, and if you're using a fuse on a motor you'd use a slow-blow fuse.

There is also something called [u]fold-back current limiting[/u] and that can be built in hardware.

EVERYTHING you want to measure depends entirely on the mechanics of your lifting mechanism.


Having experience from measuring current in order to calculate weight we even patented the method. In the end the solution was no succéss due to "side effects", special action needed to awoid things like startup current, mechanical facts in the machine etc..
I agree with groundFungus, use load cells. Even there some math, some strategy, will be needed.