DC Motor; Variable Speed Controller DIY Project. -- HELP!

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  #1  
Old 08-06-13, 04:18 PM
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Question DC Motor; Variable Speed Controller DIY Project. -- HELP!

Hi everyone,
I'm in need of some help. I'm a bit of a fish out of water with electronics.

I'm working on a project to build a "Roto Molder" for casting art pieces. I am trying to build a machine to spin molds similar to this YouTube video:
Moohead Rotocaster - YouTube

This person's Roto Molder is a massive machine.... and while i'd love to have one like that; I am building something smaller using wood.

I have a DC motor from a treadmill for this project. It is a Pacific Scientific motor ( PWM 3636-5250-7 ) ; 2.3 HP, RPM 3590, Volts 124DC 16.8AMP treadmill motor.
Here is a picture of it:
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I have a couple questions.

What is this piece on the motor?
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It was explained to me as a controller tail; but it seems to just connect to a metal plate that is screwed into the motor.... so i don't understand how it can relay info to the motor to control it.

and...

Due to my ignorance of electronics, I am trying to find a way to use this motor as a variable speed motor, without killing myself. I would like to be able to slowly turn the project at speeds from a crawl to moderately fast. My understanding is that I can buy a TREADMILL DC MOTOR CONTROLLER, like this from ebay: MC 60m Icon Treadmill DC Motor Controller MC60M | eBay
and attach a POT 5k dial to it, like this: Amico 3590S-2-502L 5K Ohm 10-Turn Rotary Wire Wound Precision Potentiometer Pot - Amazon.com and then connect a power cable, and this would achieve my goal??

If i used a 1k, or a 10k POT, would it achieve slower speeds of rpm's? (i just need the motor to slowly spin the project)

Is this thinking right? or would anyone have any recommendations on how to achieve this?


also; as a potential upgrade, could i add a simple power on/off switch like this: Amazon.com: Attwood On/Off Toggle Switch with Metal Handle: Sports & Outdoors in line to the controller unit? and possibly a timer to shut it off after 20-30 min?


as an alternative.... (simpler for me to implement)
could i use a Step Less Speed Controller, SE - Step Less Speed Controller - Electronic, 15 Amps - Amazon.com to adjust the speed of the motor, by just plugging a power cable into this unit, and then splicing that power cable to the red/black wires of the motor? (possibly with a timer on it again to stop it after 20-30 min?)


Thank you for any advice!!!!!! I highly appreciate anyone that can get me going in the right direction to a working unit. Thank you, Thank you, Thank you!

Cheers!
 
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Old 08-06-13, 08:38 PM
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Hello Theory13,

The mystery piece appears to be an optical or Hall effect sensor, there was probably some sort of disc on the motor shaft that passed through the slot every time the motor shaft made one rotation. One side of the slot is an infrared LED that shines across the slot to a photodiode, when the path is clear the signal is on, when it is blocked the signal turns off.

As for the rest of the circuit there are many details missing (specifically whether it not the motor driver is the right current and DC output to drive the motor you have), but as both pieces came from a treadmill i have to believe you're in the right ball park. If the circuit is designed for a 5k pot then a 5k pot should give you the full range of speed control. The pot is a dial that as you turn it one way the speed goes up, if you turn it the other way the speed goes down.

You seem to havd the right idea, you can try and ask for or find specs for the motor driver to see if it is sufficient for the motor you have, of you can just buy it and try it and hope it works!
 
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Old 08-06-13, 09:01 PM
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In the first link.......the Mc60m controller is only good for 8 amps which means it's not big enough for your application.

The second link shows a fully enclosed 15amp variable controller which is not only too small to run your 16.8amp motor...... I believe it's AC only.

I've been searching around. The variable control you need is not going to be easy to find. It's not a common item.

I'm still looking.
 
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Old 08-06-13, 09:22 PM
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Hi mnmattmn,
thank you so much for the explanation on the optical effect sensor. yes... there was a disk with lots of holes in it (i forgot about that), that i removed because it was just flopping around loose. -- Now that makes sense. So it seems that I'd say, its safe for me to remove that.... as i try to move forward with that motor (for my purpose).

Thank you for your response and information!! I appreciate it!
 
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Old 08-06-13, 09:37 PM
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Hi PJmax,
Wow. thanks so much for the information you've already shared. I'm glad i didn't buy one of those controllers!
Ahhhhh.... i see... so i need to find a 16.8 amp or higher variable controller, that is also DC.
 
  #6  
Old 08-06-13, 10:33 PM
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PJmax,
maybe i'm going about this the wrong way?
would you have any suggestions for a motor and controller that might be able to variably rotate max 150 lbs? (it'll probably even be under 100 lbs.)
maybe there is another product i could hack to steal it's motor from? like a sewing machine? or a microwave?
.
Thanks so much to anyone for any advice.
 
  #7  
Old 08-07-13, 03:05 PM
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Update on the project;
.
.
I wanted to thank everybody for all their help and advice on this topic.
.
I got a hold of the electrical engineer today that was in charge of these motors for the treadmill company that they were created for, and he clearly knew the motor inside and out. He was extremely helpful, and went out of his way trying to help me with a solution to this project.
.
I basically came away realizing that this motor is not the right one for this project.
The cost of acquiring the controller was going to be a problem (possibly over $500), and even then, i was going to need to run a series of pulleys to convert the timing of the power (rpm's) of the motor to my requirements.
.
I've ended up purchasing a different motor that i think is more inline with what i'm needing. It's a turnkey solution for me that is already assembled. Rotisserie_motor It was more than I was hoping to pay, but all other solutions from companies like grainger, mcmaster carr, and others were proposing orders in the +$500 range. so at just under $200 for motor, taxes, & shipping ($195.05 total out the door).... this seemed like a solution for me.
.
my budget originally was in the $40-50 range --- but researching and pairing up controllers and motors was becoming time consuming (for me/learning as i went; 5 solid days so far, with no results), and i didn't feel confident solving my problem in this way.
.
Again, I thank you for all the advice that was shared. I appreciate what I learned through all of this. Clearly this is a group of good and knowledgeable people, and look forward to learning more from you all on these forums. All the best to you guys/girls on your projects!! --- Cheers!
 
  #8  
Old 08-07-13, 04:35 PM
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You made a good decision. You would have been hard pressed to find a DC controller for your old motor. If found.....it would have probably been upwards of 150.00

They call that a rotisserie motor. That would make a pretty potent BBQ motor.
 
  #9  
Old 08-07-13, 06:04 PM
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...yup! apparently its for BBQ'ing whole pigs! yum!
 
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