Buying advice: lift 5 kg / 50 cm / 1 sec, controlled by pc

Hello there!

I need some buying advice…

What I want to do:
[li]Lift a weight of 5 kg over a distance of 50 cm within about 1 second (from bottom to 50 cm height; even 2 secs would be okay)[/li]
[li]option a: when there is a power outage, the weight should drop to the bottom (==> no motor break)[/li]
[li]option b: when the weight is larger than 5 kg, feedback to the controlling computer (this especially applies in a case where there is an obstacle in the way of the weight lifting up: I want to have the weight going back to the floor then)[/li][/ul]
All this should be programmable (computer, arduino, raspberry, …?).

What I found out:
If I omit option b (which is okay for now), it seems that a step motor would be a good solution. But in that case…
[li]can a step motor hold a weight over a long time span (an hour)?[/li]
[li]I do not know how to control such a motor with enough power. Option “AMIS-30543 Stepper Motor Driver Carrier” seems to be powerful, but how to control it from a computer? “Pololu Dual VNH5019 Motor Driver Shield for Arduino” seems to be the most powerful option, and is controllable via an arduino, but can it control step motors?[/li][/ul]

Servo motors seem to be a nice solution, too - and it seems as if a “Power HD High-Torque, High-Voltage Digital Servo 1218TH”, controlled by a “Micro Maestro 6-Channel USB Servo Controller (Assembled)” could provide me with all necessary options, right? The YouTube video is very helpful. But is option a feasible? What does the motor do when the power supply fails?

As you probably see by my questions, I am a beginner in motor-things. It would be nice to get some advice and a product combination recommendation!


Hello, Dan.

It sounds like you are trying to lift a decent amount of weight, so if you want to use a stepper motor, you will probably need one that is on the more powerful side. When picking a motor, I recommend calculating the torque requirement of your system then choosing a motor that exceeds your requirements. You might find this force and torque blog helpful.

If you decide to go with a stepper motor, the VNH5019 motor driver is intended for brushed DC motors, and is not really suited for driving a stepper motor. The motor driver is something you should select based on the specification of your motor. Once you decide on a driver, you will want to make sure that the device you are going to use to control your system can send the appropriate signals to the driver you select.

Servos do not sound like they would be suited for your application; they don’t hold position when powered down, but are not meant to be backdriven. Since you want your system to hold the load in a position, you might also look into some kind of braking mechanism.

- Grant

The mechanical power required to lift 5 kg 50 cm in 1 second is 25 watts: (mg)*h/t. An ordinary servo might provide 5 watts, so that is out of the question.

If you figure motor and driver efficiency of 80%, allow at least 35 watts of electrical power. A medium sized brushed DC gearmotor (say 1.5 inches in diameter) can provide perhaps 60 to 100 watts of mechanical power, at least for short periods