Does anyone have a solution on how to turn a knob? I have a stepper that I can control just fine, but I want it turn a knob (1cm diameter). Right now I am using tape, but was hoping for a more mechanical device, I have not found any solutions.
Hello
will fit a potentiometer control knob ?
If You detache the knob You'll likely find an axle. Then get an axle to axle adapter. Ebay has plenty if them.
Cannot detach knob. That would be bad. Don't understand potentiometer comment. The knob is 1cm in diameter and 8mm high.
Can You post a close picture of the knob?
tomstravelemail:
Does anyone have a solution on how to turn a knob? I have a stepper that I can control just fine, but I want it turn a knob (1cm diameter). Right now I am using tape, but was hoping for a more mechanical device, I have not found any solutions.
To describe something 1cm in diameter as a knob leaves me wondering! I have boxes of knobs and the smallest one is no where near 1cm in diameter.
Paul
It is a standard Master Lock combination lock like you use in the gym. I call it a knob because I am looking for a generalized solution. One idea I had was to use a 2-part shaft collar with one part glued to a shaft flange and connect the shaft to the stepper with a shaft coupler. But this requires a new collar-flange assembly for each different diameter knob.
tomstravelemail:
It is a standard Master Lock combination lock like you use in the gym. I call it a knob because I am looking for a generalized solution. One idea I had was to use a 2-part shaft collar with one part glued to a shaft flange and connect the shaft to the stepper with a shaft coupler. But this requires a new collar-flange assembly for each different diameter knob.
Then use a length of rubber tubing to connect the two.
Paul
Many people use a 3D-printed cup, like this:
If you want something more universal, take the sticky stuff from a "dashboard sticky pad" and mount that on a disk on the end of your motor shaft. When pressed against the center of a combination dial it will probably provide enough torque.
Find any cnc or laith machines workshop and design it on your own. Make a hole in the piece in which you will insert the shaft of your motor and then a screw to tighten it.
I guess I'm just surprised there is no 'off the shelf' solution, no wonder I couldn't find one. Of note, for smaller knobs, you can get a replacement 3/8" drill chuck for $10 that would work.
Thanks all!
tomstravelemail:
I guess I'm just surprised there is no 'off the shelf' solution, no wonder I couldn't find one. Of note, for smaller knobs, you can get a replacement 3/8" drill chuck for $10 that would work.Thanks all!
I am sure there are off-the-shelf solutions. You just don't know what to call them!
Look for "pin chuck". For a hand-held one, you can saw the handle off and mount it anyway you want.
Paul
Depends a lot on the type of tools you have available to you, and the accuracy of rotation you need to achieve, How about a cupped or two or three arm, forked adapter, larger than the largest knob to be turned, each arm fitted with a set screw?
This sounds like a way to automatically find the combination of a standard Master lock with an Arduino. Just set up the code to have the stepper motor cycle through the 64000 possible combinations. Assuming, say 15 s per cycle, sometime within 266 hours (~10 days) you will know the combination. You do need a way to test the schackle though.
thingiverse.com has 3D models for assorted scroll chucks that could be 3D printed and clamped on to a wide variety of knob sizes.
Search Thingiverse - Thingiverse
To open such a lock there is an "off-the-shelf solution" named angle grinder...
There are several easy solutions to open such a lock. And that's just a few of the many videos showing how to do it.
"Knob" infers tapered cylinder.
Typically wit linear knurls to enhance friction when gripping.
"Shaft" infers fixed diameter of some length.
A knob may have flats paddles wings etc
Look at a lathe chuck.
More specifically a scroll chuck.
If you want simple then a plastic mold over Your knob.
If you Want fine machining a small compact gripper possible
"I am sure there are off-the-shelf solutions. You just don't know what to call them!
Look for "pin chuck". For a hand-held one, you can saw the handle off and mount it anyway you want. "
Exactly what I was thinking, what do you call this! But a pin chuck just isn't big enough for a fat knob like this.
"How about a cupped or two or three arm, forked adapter, larger than the largest knob to be turned, each arm fitted with a set screw?"
Which is kind of what I was searching for, but I do not find any matches. Searching "three arm forked adapter" doesn't result in any hits. But it is the design I had in mind. So it looks like 3D printed specialized parts are my best option.
"Shaft couplers come in many many different sizes and size combinations."
While true, a 5mm to 10mm shaft coupling is hard to find, and is only optimized for a 10mm knob. I was hoping for a generalized solution, like a lightweight drill chuck or 3 finger gripper.
Shaft couplers come in many many different sizes and size combinations.
One more idea: Check out a Longworth chuck. The concept is exactly what you need. Unfortunately, the commercial sizes all seem to be way too larger for want you want. There are many tutorials on making your own, but again, may require more tools than you may have available to you.
There are also 3D printer models for Longworth chucks that might be adaptable to your needs. You would still likely need to buy the pins. Sometimes local libraries have 3D printers you can use for a nominal fee. Of course, this is all getting further from a "simple" adapter.