I am looking to make a bed lift for in a camper van.
I have bought 4 electric curtain rails with a belt inside:
that i want to mount vertically.
And bought 4x this motor to drive them:
Now i want to make a lightweight bed frame from aluminum extrusion and lift it using above components, on each corner a track.
I will make foldable metal arms so the bed will rest on these arms when fully down so the weight will not break the motors or tracks. It is not supposed to lift a person on the bed.
Operating it by two buttons to rise and lower the bed.
What components would i need to complete this project? I prefer readily available modules for the motor controllers as i don't want to make a circuit board.
You need drivers for the steppers. A4988 or DRV8825 drivers would work. Pololu sells the drivers and has really good instructions on their use. You will also need some sort of switches for homing the steppers at power up. They can be mechanical switches or magnetic or optical sensors.
If you use an Uno a CNC shield may make wiring things easier. It has places for 4 A4988 or DRV8825 stepper drivers and connections for 3 limit switches.
As the board would be powered off after use and the bed would be either up or down.
Of course there can be a situation that the power gets cut when lowering the bed.
Would manual lifting and lowering be a option, without limit switches?
I found this set, would that be sufficient for this?
You need drivers for the steppers. A4988 or DRV8825 drivers would work.
I have the feeling that OP needs much stronger steppers than a 1-2A one, considering they want to lift a complete bed. Though it's hard to say without knowing the torque the steppers need, and that depends on the mechanism used and the weight of the bed.
mikeisahappycamper:
The steppers have a reduction so i am hoping they will be able to handle the weight. The bed will be lightweight, hoping on a maximum of 15kg.
SO much depends on your mechanical connection to the stepper motors!!!! Make the mounting so you can use larger motors if necessary.
In engineering there is no place for "hoping", but there is ample room for "testing".
In case of your bed: start by designing the bed & a way to lower/raise it, then get the weight. Don't forget the mattress, blankets, pillows, cuddly toys, books, and whatever there may be in the bed. Double that final number for a bit of a margin.
Design a raising/lowering mechanism. Based on that, find (measure, calculate) the torque your steppers need to each raise 1/4 of the weight you calculated before. Double that torque - mind that your bed will NEVER be balanced, one corner can easily have double weight. Maybe triple that, to allow for some more friction.
Now you have the required torque, that allows you to select your steppers.
As you have your steppers, you now know the rated current of them, which finally allows you to select the stepper drivers.
Original drive motors are 45w to 75w, not sure what they mean by that.
Offhand I'd imagine them to be dc permanent magnet brushed motors.
However, I'd imagine they are also gear reduction.
Point being, as pointed out previously, your motor selection seem far short.
Well I've already got the motors and just received the stepper shield. I will make the frame and see if the motors can hold it, otherwise I can switch them to a stronger variant.
Still thinking how to connect the motors and end switches to the board, could I run it from utp cable or would there be too much current running through the wires.
So a update from me regarding this. I've assembled the guide rail, modified the motor shaft and connected it to the cnc shield.
I also added some weight (7kg) to see if it would hold. As the gear ratio is 50:1 it's not particularly fast however by adding end switches it would be a case of pressing a button once and all 4 motors would lower or rise at the same time until they hit the end switch. Any thoughts on this?
