Turning a spinning wheel electric

Long story. The short form is that I'm going to add a pulley that will spin the big wheel of the spinning wheel (which is called the fly wheel) in order to motorize the whole wheel. Yes, I know, commercially made "espinners" aren't run that way, been there argued that.

I've not done much electronics or robotics type stuff. So I'm constantly running into new road blocks as I work my way through it all.

I've mostly got it figured out which motor I need.

I need to to turn off, turn on (via switch), and spin at a variable speed, controlled by either a knob or (preferably) a foot pedal (like a sewing machine).

I'd been planning on using an Arduino Uno, but its looking like that in order to wire in the variable speed I'd need a separate speed controller? Does this sound right? Or am I over thinking it and I can do it all with the Uno?

You should be able to use the PWM to control the motors speed.

I agree with Jack. Since the motor will only travel in one direction, PWM and a MOSFET would take care of the motor driving, as long as it's a DC motor.
A pedal incorporating a pot would be fairly easy to implement for the speed control user input.

OldSteve:
I agree with Jack. Since the motor will only travel in one direction, PWM and a MOSFET would take care of the motor driving, as long as it's a DC motor.
A pedal incorporating a pot would be fairly easy to implement for the speed control user input.

Please define "MOSFET". I'm still trying to figure out most of the acronyms!

I ran across THIS, which should be easy enough to turn into a pedal if I understand it right.

And yup, DC motor, THIS one infact.

ruthcatrin:
Please define "MOSFET". I'm still trying to figure out most of the acronyms!

I ran across THIS, which should be easy enough to turn into a pedal if I understand it right.

And yup, DC motor, THIS one infact.

A MOSFET is a type of transistor - Metal Oxide Semiconductor Field Effect Transistor.

An Arduino pin has limited current capabilities, so the MOSFET is used, connected to a pin, to actually drive the higher current motor.
I'll draw up a quick diagram and post it shortly.....

Ok, this whole 1 post every 10 minutes thing is beyond annoying....

Gripe out of the way, thank you! I have a feeling I'm going to be doing alot of posting of questions over the next few weeks as I pull this whole thing together and try to assemble it without frying anything.

ruthcatrin:
Ok, this whole 1 post every 10 minutes thing is beyond annoying....

Gripe out of the way, thank you! I have a feeling I'm going to be doing alot of posting of questions over the next few weeks as I pull this whole thing together and try to assemble it without frying anything.

Ha. Yeah that used to bug me too. Doesn't happen any more. In fact, I'd forgotten all about it. It might only happen while your post count is below a certain threshold. Not sure.

Here's that simple diagram, (attached).

MOSFET Motor Drive.JPG

I just checked out your links - that throttle control is pretty much what I was talking about - a pot operated by a lever. Should be easy to use it as a pedal.

And I see your motor is geared for 500 rpm. That's about 8 revs per second. It sounds fairly good for what you want. You wouldn't want it to go any faster than that, I wouldn't think.

Edit: On second thought, if you want to use a small pulley on the motor and a large one on the wheel, that motor might not be fast enough.
It would pay to do a few calculations first. Step 1 is to work out the maximum speed that you want the wheel to turn at. Then decide the approximate size of the pulleys you want to use. Then, choose the motor.

For instance, if you have a 10:1 pulley ratio, the motor will need to turn 10 times as fast as the actual flywheel. A 500rpm motor would only give a flywheel speed of 50rpm, less than 1 revolution per second.

Awesome on the throttle control

And good on the motor. Figuring out the maths to figure out what I needed out of a motor was a massive pain. Wish I'd thought to wander through here then (I found another forum, but apparently not one thats frequented much any more, the folks responding were helpfull, but a wider variety of response would have helped). And yup, thats actually a bit fast if I did my math right, but it gives me room without being excessive.

Ok, looking at your diagram, and additional other info on MOSFETs. Can you point me towards one that'd be appropriate for what I'm doing?

ruthcatrin:
Awesome on the throttle control

And good on the motor. Figuring out the maths to figure out what I needed out of a motor was a massive pain. Wish I'd thought to wander through here then. And yup, thats actually a bit fast if I did my math right, but it gives me room without being excessive.

Ok, looking at your diagram, and additional other info on MOSFETs. Can you point me towards one that'd be appropriate for what I'm doing?

Ruth, check the edit on my last post regarding the motor.
Any logic-level MOSFET that can handle 5A or more would do. That's well over the current of the motor you linked, but it's best to wait until you're sure about the motor before determining the exact MOSFET.
I'm in Australia, so don't have the same suppliers to recommend one for a particular MOSFET. I guess you're in the US. Someone else might be able to help with that.

N.B. A 'logic-level' MOSFET switches on at a lower voltage than a standard one, making it well suited to switching with an Arduino.

If you Google "foot pedal potentiometer" you'll get lots of hits.

I think a lot of the foot pedals use heavy duty pots which are used to control the current directly. If you're just using the pot as an input to the Arduino, you don't need a heavy duty one.

Something like this foot pedal should work. It's kind of pricy. I bet there are less expensive pedals which would work.

I think this MOSFET would work for this application but I hope someone will confirm this.

DuaneDegn:
I think this MOSFET would work for this application but I hope someone will confirm this.

That looks perfect Duane. And since it can handle a continuous 22A even at 100C, suitable for any motor that Ruth might use.

I would recommend getting a pre-made pedal if you could find one - mechanical stuff like that that's simple conceptually can be a real pain in the ass if you don't have access to machine tools.

The current on that motor isn't that high, so you shouldn't have any trouble finding a logic level MOSFET that'll work. Be sure the MOSFET is actually logic level (Rds(on) specified at Vgs=4.5V or lower, according to datasheet). A lot of unscrupulous vendors sell IRF510 modules as if they're okay for use with Arduino, but they don't turn on all the way with 5v. (As it happens, I sell logic level MOSFET's on breakout boards in my tindie shop big ones and little ones). Since you're controlling the speed with PWM, it's best to leave some extra margin. If you want a through-hole stand-alone part, I like the IRF3708PBF - it's available in TO-220, very beefy, and it works decently even at 3.3v on the gate (making it one of very few through-hole MOSFETs that works with 3.3v or lower).

Oh, and you want to switch the low side of the motor, not the high side - to switch the high side, you need a P-channel MOSFET (more expensive for equal performance), and you'd need a transistor to control the gate, because "OFF" for a P-channel MOSFET would be the positive supply voltage, (+12v), which you couldn't connect to Arduino directly... (N-channel mosfets switch the low side, P-channel for high side).

50-100rpm is the range where most experienced spinners that I talked can treadle (pedal) their spinning wheel at (I've never calculated it for myself, and cannot now due to ankle problems), so I used 75rpm to calculate from. So I want a velocity of 4.65 ft/s (1.417 meters/second?) if I did my math right.

The weight of the flywheel is 1.234kilo with a diameter of 14.25" (36cm)
torque 22.21k/cm

Pulley size is yet to be determined, and yes I understand that will make a difference

And yup, I'm in the USA, but that gives me a starting point to look at thank you!

Try this one

as long as the DC voltage level is in the right range.

Duane & Crossroads, thank you for the links!

DrAzzy:
Oh, and you want to switch the low side of the motor, not the high side - to switch the high side, you need a P-channel MOSFET (more expensive for equal performance), and you'd need a transistor to control the gate, because "OFF" for a P-channel MOSFET would be the positive supply voltage, (+12v), which you couldn't connect to Arduino directly... (N-channel mosfets switch the low side, P-channel for high side).

Thank you for the links, but that last paragraph lost me again (not hard to do, sorry), "low side" and "high side" of the motor?

ruthcatrin:
Thank you for the links, but that last paragraph lost me again (not hard to do, sorry), "low side" and "high side" of the motor?

With no MOSFET

+12V
|
Motor
|
Ground

With high side MOSFET

+12V
|
MOSFET (P-channel)
|
Motor
|
Ground

With low side MOSFET

+12V
|
Motor
|
MOSFET (N-channel)
|
Ground

DrAzzy:
Oh, and you want to switch the low side of the motor, not the high side

DrAzzy, this was covered in the small diagram I posted, using an N-channel MOSFET for low-side switching.

And now there are a choice of two suitable MOSFETs - Duane's recommended FQP30N06L, and your IRF3708.
Either is fine.

Edit: Then there were three. :smiley:

CrossRoads, your suggestion is cheapest and smallest, but being surface-mount it's harder to solder, (real tricky on veroboard), and can't easily be tested in a breadboard before soldering up a final circuit.

Ruth, take your pick.....

And as mentioned, the circuit I drew is low-side switching. Ignore the P-channel and high-side switching stuff - it'll just confuse you for no reason. :slight_smile:

OldSteve:
And as mentioned, the circuit I drew is low-side switching. Ignore the P-channel and high-side switching stuff - it'll just confuse you for no reason. :slight_smile:

Hah, thats not hard! I had done a couple of little kids kits, literally just plug point A to point B and presto have a little robot sort of thing. I didn't realize what I was getting into!

ruthcatrin:
Hah, thats not hard! I had done a couple of little kids kits, literally just plug point A to point B and presto have a little robot sort of thing. I didn't realize what I was getting into!

Nothing is ever as easy as it seems from the outside. :slight_smile:

Still, in this case it's pretty straightforward. That circuit isn't too hard to put together, and from the programming point-of-view it's fairly easy too.
Basically, you just use 'analogueRead()' to read the input from the speed control pot, which returns a value in the range 0 to 1023, then 'map(,0,1023,0,255)' to convert the 0-1023 to 0-255, then 'analogWrite()' to send the value to the PWM output pin and the MOSFET.
We can guide you along the way.