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Dr.Arz
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Slow high torque electric motors for stirrer?
Where can I get high torque low RPM electric motors, with or without rpm adjuster? I know brushless DC are most ideal and freely adjustable for
stirring purposes and they give extremely high torque even too much but they tend to be expensive.
What I am looking is something OTC. I can get 600-1200 watt continous use eletric motors from pumps and other stuff for very low price (10-50) but
they all work at 50hz which is just total kill for overhead stirrer.
Air fan motors turn slower than that but they are weak too. 40W may not be enough to turn against the vacuum seal friction.
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Magpie
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I agree that there is a need for such a stirrer. I have a Wheaton overhead stirrer but it is designed for tissue slicing, I believe. It's great if
you want high rpm (500-1000) but not so good at low rpm, say around 100.
I would like to build my own stirrer. But, as you say, I need to identify the right motor. Ideally it would be controllable.
[Edited on 28-10-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Oscilllator
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I personally use a "WICTA DC GearMotor 12V" that I bought for an unrelated project. The thing is 12V but it runs fine on an 18V cordless drill battery
and is virtually unstoppable. Seriously, if you want a motor to stir a 1L flask of wet concrete than this is the motor for you. It cost me $14AUD, but
you might be able to get it for less, depending on where you look.
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Magpie
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Oscillator that sounds like a great price.
Perhaps you have identified a good source for all that is required, ie, a cordless drill. It would have everything: low rpm high torque motor with a
chuck, speed controller, and battery. 
(I'm assuming the above motor would be brushless, but I don't really know if it is or not.)
[Edited on 28-10-2014 by Magpie]
[Edited on 28-10-2014 by Magpie]
[Edited on 28-10-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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diddi
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raid an old printer and get a stepper motor. the stepper motor driver circuits are available complete for about $5. infinitely variable speed and good
torque.
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Oxirane
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Stepper motor sounds good too.
But if you have got common 220V electric motors, what if you put a reduction gear between it? A 5:1 ratio would already bring it to 600rpm. I use RPM
around that for most everything I do and if you get 2-3 sizes of small gears you could vary the speed easily. Gearbox is not hard to construct and
small gears suitable for that are available all around. If you go hardcore, 3D print them.  A small electric motor from drill, pump, fan etc. is very cheap and can probably be found from junk and with reduction it gives huge
torque, most likely even that 40W fan motor would be enough. Beware it won't run your setup off the table it it gets stuck. 
[Edited on 28-10-2014 by Oxirane]
[Edited on 28-10-2014 by Oxirane]
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zed
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Air motors are wonderful. Explosion proof too. Problem is, they require a lot of air.
I have a pretty nifty compressor, but at its maximum output, it still isn't really adequate to supply enough air to even a smaller air motor.
So, do you have a big-ass air compressor? Or, a couple of smaller, but pretty good ones?
[Edited on 30-10-2014 by zed]
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jock88
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Cordless drills can be found in the dump sometimes as the batteries have given out.
The one with a torque setter on them would be great as you can limit the torque of needs be.
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careysub
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Although repurposing junk into something useful is an admirable and truly rewarding activity, the investment in time (finding that "cheap" motor,
adapting it to the task) can be significant.
You can set an upper limit on cost at $19, and make the process of acquiring by considering the cheap Harbor Freight variable speed drill:
http://www.harborfreight.com/38-in-variable-speed-reversible...
Using the trigger lock you can set it run at a continuous, fairly slow speed.
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Magpie
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I looked at some cordless drills at Ace recently. These were brand-name drills like Milwaukee, etc, and were about 3-5 times as expensive as the HF
Drillmaster.
The Ace drills had a 17 or 18 position ring that is used to set the speed. Then there is a high and low range switch giving you a total of 34-36
different speed settings. I assume that these drills are DC brushless.
The HF Drillmaster has a cord so I'm assuming it is an AC motor likely with brushes. I think that we agree that for lab stirring brushless is
desireable (or mandatory) as many of our concoctions are flammable. Correct me if I'm wrong.
The single most important condition for a successful synthesis is good mixing - Nicodem
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careysub
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Brushless is no doubt better - but if this really is absolutely necessary you must also confirm all your electrics are sparkless (fume hood fan,
lighting, hot plate if using, etc.).
Checking some cordless drill specs (like 12V Black and Decker) I see that they are NOT brushless. So being cordless is no guarantee.
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diddi
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stepper motor controllers are externally clocked which means that you can control the RMP infinitely from 1 rev per day to thousands RPM (eg hard
drive 7200rpm) a lot of steppers use 4 wires which is a common output config for the generic stepper control boards. you can obtain quite high
resolution of angular step with very little investment. many steppers have a resolution of 1.8degrees/step (200 steps per rev) but the stepper
control circuitry is able to generate a series of microsteps (which sort of feels counterintuitive to a digital motor) by tweeking the overlap of
power to the motor coils . so you can get smooth stepping rotation with up to 200 x 16 increments per 360 degrees. torque is good, but the holding
strength is compromised at the pseudo analog positions between native digital steps (but this would not be a problem in your application)
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violet sin
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I service our ac screw guns at work. They have brushes for sure. Same goes with the rotozip (drywall router by dremel). I don't know of a single
brushless version we use.
Also magpie, the 17-18 position twist ring is most likely setting the torque before the clutch slips. Saves you from snapping bits or screw heads
off. Should be 1 - 3 speed slide selector, depending on the model. With the torque selection shown on the ring as a series of numbers followed by a
drill bit icon, and maybe a hammer icon as well. Numerical slip for installing fasteners(screws), drill icon is for drill bits with max torque and a
hammer icon for the hammerdrill setting for concrete or long screws.
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Magpie
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Yes, I see. Thanks.
There is quite some information on YouTube about cordless drills and how to disassemble and hack them. Here's an informative one that shows that
Milwaukee makes a cordless drill that is brushless:
https://www.youtube.com/watch?v=x-OkkjXVfGw
The single most important condition for a successful synthesis is good mixing - Nicodem
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chemrox
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I have one I'll sell you. It's cone drive stirring motor for when the material is too viscous for stir bars.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Magpie
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diddi I think a stepper motor would make a fine stirrer based on what I have read so far. Do you have to buy a separate power supply/control board
for these motors, or does that come with the motor? Would an arduino work? What is the user interface with the controller?
The single most important condition for a successful synthesis is good mixing - Nicodem
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diddi
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I bought 5 of these recently:
http://www.aliexpress.com/snapshot/6208985439.html
the board has direct connection to a range of steppers and offers up to 16x intermediate steps as per my previous post. it will break the budget at
nearly $2
the power supply is quite easy. I use old computer power supplies. they work fine and with the number of putas thrown away it wont take long to find
one.
the stepper motor connects to the driver board via a standard 4-pin connector. the stepper has an array of coils inside which are wired in 2 "banks"
1 pair of the 4-pin wires drives each bank. the controller board send alternate signals to the banks which advances the stepper 1 step. this
"advance" signal is driven by the "clock" input on the controller board. you can use arduino if you like, but by far the cheapest and easiest is just
to drive the circuit off the old faithful NE555 and 2 small caps and a resistor (another bank buster at about $1)
you really don't need the high resolution stepping ability of the controller board for a stirrer, but it is simple to invoke, by adjusting the inputs
on the board. variable speed stirring is easily accomplished by adding a single variable resister ("pot") to the 555 circuit across pins 7 and 8. if
you want to be fancy, you can even use a counter/display chip like ICM7217 to display revs to about +-.01 RPM
any more details I can help with?
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Magpie
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Thanks diddi for providing all that information - it will take me a while to digest it as this is all new to me. Then I'll probably have more
questions.
I'm surprised at how little money may be needed to put together a rather nice stirrer. It looks like a fun project.
The single most important condition for a successful synthesis is good mixing - Nicodem
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diddi
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well I am now inspired to build a demo on a prototyping board, so I can show and label the parts. I have a pair of steppers from a HP scanner and all
the other bits lying around, so hopefully I can post a pic in the next day or so.
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Magpie
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Wonderful! That will really help me.
The single most important condition for a successful synthesis is good mixing - Nicodem
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diddi
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well here is my demo. it runs!
using standard motor
MINEBEA NEMA 17 STEPPER MOTOR 42MM 4-WIRE
as used in lots of printers etc
speed set is really slow (about 20 rpm) but easy to change. the torque was so strong that when I tried to grab the gear and stop it, I cut my finger
to bleeding
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Magpie
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That's awesome diddi. I'm going to start scrounging parts right away. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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I had unbelievable luck this morning. I walked into Radio Shack to see what parts they had. While there I mentioned to a young man that I was
looking for a junked printer and a junked computer. He just happened to have 5ea in his apartment and offered to give them to me for free. I took
2ea. He works for an internet service co. and offered me more parts and technical consultations also. What a deal! I gave him $5 and felt guilty.
I've already torn apart the small HP Invent printer (2007 model). I salvaged 2 stepper motors and 3 ss shafts, plus some nylon gears. One shaft is
1/4" x 16". The motors have the following numbers:
motor #1: C9000-60005; 1030048; 3H2911 86
motor #2: C9045-60001; 1030151; 3H2263 86
Do these numbers mean anything? Can they be used to find the motor specs? After seeing the stepper motor identified below I think these may not be
steppers.
The 2nd "printer" is actually an HP copier. I just pulled off a serious stepper motor:
MINEBA "ASTROSYN" STEPPER, type 17PM-J802-G1VS; NO. T5815-01 A; DWG NO. AX05 0204 A; 3.1V; 1.14A; 1.8 deg
This motor is a cube about 2" on a side w/laminations; there's 6 wires coming off from a plug-in
[Edited on 2-11-2014 by Magpie]
[Edited on 3-11-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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diddi
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MINEBA "ASTROSYN" STEPPER, type 17PM-J802-G1VS; NO. T5815-01 A; DWG NO. AX05 0204 A; 3.1V; 1.14A; 1.8 deg
same brand as mine- the 17PM shows it is same type as well. 1.8deg = 200 steps per revolution. the rest is junk to do with the shape of the gear on
the end etc. the only problem is it is the 6-wire type and the controller board I showed is the 4-wire sort, but that is fixable by omitting 2 wires.
this site
http://www.eminebea.com/en/product/rotary/steppingmotor/hybr...
has the data. my interpretation is that 1 pair of wires can be made from pins 1 and 3; the second pair is pins 4 and 6. this converts back to 4-wire
model so you can use the controller I used! the capacitors and resistors for the 555 circuit can be ripped out of any computer power supply, and
since you now have 2 of those, you should look for values of the capacitors of around 10 - 47uf @ <50V (need 2, same or different). resistor (for
non variable speed might be about 2.2K (red, red, red) or if it is to be variable speed, raid an old stereo/radio etc and get the volume control
dial. it will have 3 tags/wires attached. I will post pic with variable speed later. if variable speed, you still need a resistor (<47 ohms) eg
orange, orange , black or red,red, black or brown, black, black.
if you would like a circuit board design, I can post one to scale and you can make it.
another thought: if a few are interested I can design a board, assemble the whole controller and user just plug in their 4-wire plug, ready to go.
it would be fairly lite so postage would be cheap. I am in Australia.
not that I am advertising for work. I have lots to keep me busy, but if electronics scares people off, I don't mind.
the other motors with 90xx numbers are analog motors. (no good for this application)
you can tell steppers by 1) more than 2 wires and 2) if you turn the shaft gently you can feel a sort of internal "clicking". analog motors don't
click.
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m1tanker78
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Stepper motors are great. If for some reason you can't find one or the driver, you might also consider salvaging a synchronous motor from a microwave
oven. These run at low RPM and normally connect directly to 120/240 depending on where you live.
Yet another option would be to source a windshield wiper driver motor or even a power window motor from the junk yard. Both offer high torque and low
speed. If you have an adjustable 12V power supply, you have your speed control. They do tend to sink quite a bit of current though.
Tank
Chemical CURIOSITY KILLED THE CATalyst.
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