I have a question regarding the project I'm working on. I have to motorize wardrobe, because it is kinda heavy to move it.
I have figured out, how to attach motors and what stepper motors (NEMA23, 3Nm). I need, but now, I'm struggling with sensors, to make it easy and safe to operate.
I wanted to use 4xTTP223 touch sensors behind thin pieces of wood veneer (two on each side of the wardrobes so I can open it from either side ((I'd like to place them on the wall, so I don't have to deal with moving cables))), 3x End stop sensors to make it stop in end positions and a current sensor for motors if the wardrobe would hit smth so it will stop automatically (hoping, that my thinking behind it, that the motor will draw more current if they are getting overloaded).
The problem is, that it is a lot of things I need to connect to arduino, so I will use Arduino Mega and other problem is, that the cables can be pretty long (dimensions of one wardrobe are roughly 90cm wide, 2m long and 2,3m tall). Im especially worried about the touch sensors.
Do you have any suggestions, for a solution? Maybe I can use a second Arduino (as shown in the picture) and make it communicate with the main one, which will be mounted somewhere on top of the ceiling, so it is close to digital stepper motor drivers (DMT556) and the endstop sensors (their position is showed on the edge, but in reality, they will be closer to the chain drive).
Thank you very much, I'm new to whole mechanical and electrical topic and I would like to consult the solution with someone more experienced.
Why stepper motor instead of normal gearmotor? Do you need to know position when moving?
Those touch sensors are probably not best choice, especially with long wiring.
Use good shielded cables for limits and sensors.
I would try to design the setup one way or another with just one arduino, connecting two together with certain distance in noisy enviroment is only complicating things further.
I don't think you can get good current-sensor feedback from stepper motor setup, they don't work like "normal" dc motors. They are drawing current even when still. Your driver is limiting it based on your settings.
No no, I definitely dont want to ask for design service, Im really sorry, that it sounded like that, I'm really sorry. I want to work on it myself, but I'm newbie to this, so I wanted to ask for some tricks, if somebody encountered same difficulties
I thought about using normal geared motor, but it is kinda harder to understand, what the motor can or cant do and since Im in foreign country, its harder to find it and order it, also I wanted to have more control about the speed, and steppers can usually deliver their peak torque in much lower rpms, so stepper motor was easier to find and buy.
And since you are asking, maybe it is good idea, to implement the precision movement, so I dont have to rely only on the endstop sensors (and I saw, that they could be weak link in the chain, because the wardrobe is really huge and heavy and some small endstop wouldnt be long-term solution, or more like the movement of such a heavy thing wouldnt stop immediately, so it would hit and maybe break the endstop, so I will rather use it use as a backup, if the precision positioning failed).
Shielded cables sound good, I will definitely create a test bench before actual instalation, So I can proof the concept and test, that the sensors can work over 2-3m
That's not really true. It's much harder to understand what steppers can do. Gear motor has a gearbox with a correct ratio for speed and torque. Speed can be also reduced with motor controller when needed. You have options of AC or DC. Also you can use current-sensing.
Think of linear actuators.
Steppers are complicated, for that load you need huge power supply and expensive drivers.
Stepper draw always it's set current, independently if moving hard or staying still.
Think twice before deciding. I woul'd never ever use stepper to do what you are building. I use them in CNC with a positional precision of 1/10mm.
For endstops you can use springy mechanical switches, optical switches or hall sensor.
You can slow down movement when coming near to endstop, not to hit it "full speed". Can be easily done time based without extra sensors. As extra security you can have current sensor.
Ps. My electric gate (linear actuator without encoder) doesn't have any sensor switches, it's all done with current sensing. It stops when current spikes. If it expects (time based) that it is about to hit mechanical end it slows down and when current spikes, it reverse for few millimeters.
Hmm, now you really got me. I thought, that it will be easy with the stepper motor, but the benefits of basic BLDC seems much higher I will give it a shot and try to find some suitable BLDC motor to buy. Or do you have some tip, where to look for motors? When it comes for parameters, Im looking for smth with around 100-150 RPMs, preferably 10mm shaft and around 1.5 Nm. Im also not sure, if creating own 3D printed gearbox would be fine for longevity, so that's also why I wanted to use just the stepper motor without any gearbox, because it has 10mm D shaft and there is almost nothing that could go mechanically wrong.
"1.5Nm"?
I don't know anything about your mechanic parts. What are you actually trying to move??
I imaginedt that you have some kind of "sliding room"...
Anyway, you are not limited to bldc, just normal dc motor or even ac-motors are ok.
With factory gearbox, that's the most stressed part.
Hihi, when I did the calculations, it came out around 1-1,5Nm. I’m moving wardrobes. On the picture you can see two "boxes" which are actually made from steel profiles, the vertical ones are 5x5cm, the horizontal ones at the top are something like 5x10, so the actual weight of that can be very high, I assume it can be around 300 maybe 400kg and when we measured force needed to start moving the wardrobe it was around 6-7 kg empty and without the wooden parts, so I assume it will be a little bit more.
It will be maybe a bit harder task, then I thought at the beginning, but we will see. I will definitely post the result.
Numbers don't match.. Or you use lead screw ?
Anyway, don't let motor specs fool you. Dc motor can have nominal torque of 1Nm, but stall torque of >10Nm. Nominal means you can drive it 24/24 without heating it too much.
$30 cordless battery drill have around 50Nm max torque.
Wait, you mean it is too low?
I want to move it with 8 teeth sprocket wheel (08B chain) and the wheel is around 35mm in diameter. The good thing for me was, that the wheel and the shaft on the stepper match, so it will be much easier to connect. Also, another good thing is when the motor is not in use, I can turn it off on the stepper driver, so it won't consume that much power. And lastly, if something goes wrong, it will be much easier to move the wardrobe when there is no gearbox or anything like that I guess (that's why I dumped the idea with the lead screw, which would be probably the best solution otherwise).
Only you can know if it's correct... Looks low to me for the 300-400kg weight to move, but I don't know your mechanics. You can get that from toy-motor.
Shaft coupling should not be an obstacle if you manage to build all this. Normal dc motor doesn't consume anything when not running, stepper does if you don't disable it from driver.
Manual moving without gearbox is advantage ofcourse.
Ahh, no it really should be that low, because the wardrobe is hanging on heavy-duty linear rails, on which they are moving and with hand scale we figured out, it takes just around 6-7kg to move. And if I use a small sprocket it takes just around 1.5Nm to move.
I would definitely do it differently if it were a project for my home, but it isn't and I also don't have all the fancy things to build it, as I am in a different country, so I am trying to find the easiest solution which will do the thing.
I think I have an answer for what I wanted (and also many more questions that will be lying in my head from now on ), but I will give it a shot and we shall see how it goes. I will let you know, how it went.
I will give it a shot and try to find some suitable BLDC motor to buy. Or do you have some tip, where to look for motors? When it comes for parameters, Im looking for smth with around 100-150 RPMs, preferably 10mm shaft and around 1.5 Nm. Im also not sure, if creating own 3D printed gearbox would be fine for longevity, so that's also why I wanted to use just the stepper motor without any gearbox, because it has 10mm D shaft and there is almost nothing that could go mechanically wrong.
), but I will give it a shot and we shall see how it goes. I will let you know, how it went.