Hello!
So, I've got this desire to be able to move my grow lights up or down about 6 foot throughout the course of the grow.
My thought process was to have a stepper motor that rotates to either take up the rope holding the light, moving the light higher, or rotates to release rope holding the light, moving the light lower.
The struggle I'm having is placement of the motor in relation to the applied weight holding/moving the light.
Initially my very simple thought was to place a spool on the end of the stepper motor, and have the rope wrap around the spool according. But a direct weight placement on the drive shaft of the stepper motor would cause an uneven weight distribution on the shaft, and what I would assume to be not good at all. In other words, if the light is hanging from a rope that's wrapped around my motor shaft, there will be an uneven (downward force - gravity) applied to the shaft. This is not desirable.
So then my thought process was, in order to get even weight distribution on the shaft - I would need it to pull in parallel with the shaft - and in comes the Idea of a threaded rod. A threaded rod would achieve the weight distribution solution I'm looking for, but I'm not sure how I'm going to get 6 foot of travel distance unless I've got a 6 foot threaded rod... which seems impractical?
I'm thinking there is a combination of gears, or something that I can use, to make this happen - but I'm at a loss for what the answer is?
I figured someone on this board probably has the experience, or engineering background, who can quickly identify a solution? My I'm being too optimistic!
Either way, I appreciate any help you can provide!
Thanks.
Issue has been fixed in rel 3.29f uploaded yesterday
Hello,
Found the issue with the Hbridge setting, going to fix it in the next release!
Absolutely.
And as someone who's spent a portion of time traveling across the world, I think your ability to communicate these concepts in your non-native language -ENGLISH AT THAT - is remarkably well. So cheers to that!
This makes perfect sense to me. Thinking out loud - I can set a min of -120, and a max of 120, for a total travel of 240. And this setting will allow me to go down -120 and up 120 from initial position. I get it. I think the more stable approach would be to set the initial position (min = 0) at the very lowest I want it to ever be, and then move it up until I hit my top threshold, which value I'll place for the Max.
Ops... I see a SW problem there :).
Apart from the SW issue which I'll try to replicate and fix, the HBRIDGE has a Min and Max value in which the output is allowed to range. For example if the Max is set to 30 and the Min is set to zero, then the motor is allowed to rotate in one direction because it assumes to be in the position Zero, as it cannot go below zero it is free to run only in one direction. This can be changed by setting the position manually as you tried to do.
In practice, it is important to define the Zero position in the Software which will correspond to actual zero position of the motor then tune the Max according to that position. Notice that the Min can also be a negative number.
Hope this makes some sense, I'm fighting with the English language.
Regarding the SW issue, can you send the screenshot of the Hbridge Hardwaresetting you are using, would like to replicate the error if possible.
Yep, I took note of that but bypassed for the time being as the light will only ever be moved manually (no automation algorithm involved). BUT! The switches are so cheap and can be here tomorrow - so I went ahead and ordered some. One thing I don't quiet yet understand is when does an HBRIDGE end up "Out of Range"? It seems I cannot move the motor one direction, without first moving it in the opposite direction? Why is this?
Also, the "Reset HBRIDGE Position" button doesn't work for me - give Internal Server Error:
Minor issue, I was just hoping to understand the logic behind "Out of Range" when trying to move the motor.
Thanks!
Very good!
Forgot to mention about the end switches... It's very important to find a way to install the end switches, they are normally used to stop the motor at a certain point but most importantly as safety feature.
Alright. So I've got a 12v DC wormgear connected to the relay and it's operating as an HBRIDGE as it should! GREAT!
Now I'm just waiting on a shaft to get here then I can put this thing into action!
Thanks again!
I seee... I do know how to rig up a series of pulleys to multiply the applied force if necessary. My main challenge was to figure out a locking mechanism.
I'll check this out!
Thanks!
I found this, it uses worm gear, which in some extent are self locking:
30 lbs are not so ligh, anyway it all depends on the diameter of the spool. Larger spool diameter will require more torque on the motor both to bring the lights up and to hold them, but it will go faster. Smaller diameter will lower the requirement of the torque on the motor and will go slower. There are several types of this motors for different cost/torque requirements.
So, the light would be about 4 lbs currently. But lets say I wanted to be able to support 30 lbs.. I don't feel safe leaving that load on the shaft of the motor. I'm trying to think of a ratchet/locking mechanism - or a brake - something that will allow it to rotate both ways, but hold it once powered down. What comes to mind is a ratchet/locking mechanism like that used in a winch - but I'm not sure how to engineer it so that it will go both up and down. Or maybe there is some other way to go about applying a brake when not moving up or down. Hmmmmm..
Ahhh. Good catch about the free-fall of the lights after you "free-them". I was trying to come up with some locking mechanism that works both ways but have not yet arrived at that solution. I didn't think about the fact that the motor will be free spin when current is not applied. The DC motor sounds like the most ideal route. As far as precision, I would like to be able to move it to within +/- 2 inches. Really though, it's not that important.
Also, not needing the additional driver is a big plus.
I guess for now I'm off to find an ideal DC motor and gearbox/locking mechanism.
Thank you sir!
Hi There,
I like this idea to automate the light height, it does make sense for plats that grow tall very quickly (for sure not for salad ;).
I agree about the shaft with the bearings, looks like a good solution, simple enough. This might allow to use also two spools to better balance the light.
For the transmission of the rotation from the motor to the shaft I normally use this type of couplers:
There are different size with different holes diameters on each side.
They also allow to have not perfect alignment of the shaft and the motor rod.
Clearly this is ok for not so heavy load and no so big shaft :), there is no reference in you post about the weight of the lamps.
Does the stepper motor have a mechanical gear reduction?
I ask this question because without the gear box the stepper motor will move quite freely after you "free them" and your lamp will fall down.
Initially I used to control my greenhouse window with a stepper motor, but lately I implemented other controls using normal DC motors, there is a big variety of DC motors with gear boxes, the DC motors do not require special drivers. Furthermore the reduction box keep them in place. They are not as precise as the stepper motors, but is the precision required in this application?
Below a video that I made some time ago about it.
Alright, so I've got the idea to put a shaft between 2 bearings mounted on the ceiling, and have a spool on the shaft to hold the rope of the light. This way the gravitational load is placed on the shaft, who's load is placed on the bearings mounted to the ceiling. ... Now to devise a way to turn the shaft. ...