Hi !
I got 3 motors from a fairly new printer, I wondered if these could be stepper motors or not.
When I turn the shaft I feel like some steps at every 1/2 degrees. Is that the sound (feel) of a stepper ?
Is this 94V means they run at 94V ? That sounds crazy for such a small motor...
Also, they have only 2 pins on them.
Thanks !
No, unfortunately newer printers dont carry steppers any more, those are DC motors, what you are feeling is probably the brush's contacts in the rotor.
Hmm I was thinking about building some CNC mill with that. I guess with DC motors that can't be done, right ?
No - those are brushed DC motors, and likely rated for 6-12 volts, given their apparent size...
As far as the "feel" of the motors - what you are feeling is called "cogging", where the poles of the armature (the thing that turns) line up with the magnetic field of the permanent magnet poles in the motor. Typically in such small motors there are 3 or 5 poles on the armature, and two poles on the stator (permanent magnets).
A servo motor does have a "cogging" feel to it, but it will feel much more "precise", as the stator and armature of the stepper motor has a ton more poles.
Something to keep in mind on a brushed DC motor is that the greater the cogging effect, the more it takes to get it spinning (current and voltage)...
enjoyaol:
Hmm I was thinking about building some CNC mill with that. I guess with DC motors that can't be done, right ?
Sure it can - in fact, in most industrial CNC mills, stepper motors aren't used - because they aren't fast enough.
Instead, continuous rotation motors are used, along with pulse encoders; instead of pulsing a motor a certain number of steps (as with a stepper), the motor is instead spun (via an h-bridge or other controller, depending on the motor type), and the pulses from the encoder are counted. As the count nears the final count needed, the motor is gradually slowed down (to prevent an overrun condition - electronic braking might also be applied). By "gradual" I mean in terms of the electronics and motor; to a human it looks pretty much like an "instant stop".
I'd be willing to bet that if you examined the printer those motors came out of, you would find similar pulse encoders (as the printer would need them too)...
Well, I'm looking at the electronics of the printer and don't find much things in it (many big boards with multiple micro controllers on it, that's it).
I got one or two thing which is strange and I'm not sure what it is, I posted the pictures of the components to another section of the forum maybe you will see if that's related ?
Post is here : http://arduino.cc/forum/index.php/topic,75012.0.html
Also, when I check for something which could look like a pulse encoder for a DC motor, I see that all dc motors have a special enclosure like on this picture :
(Source wikipedia)
None of the motors in the printer look like that, that is, with a special tube that is on the right of this picture.
Edit: changed the image so that it's smaller..
Senso:
No, unfortunately newer printers dont carry steppers any more, those are DC motors, what you are feeling is probably the brush's contacts in the rotor.
No steppers? That's interesting! What the preferred method now? Servos? Are steppers becoming phased out generation? - Scotty
scottyjr:
Senso:
No, unfortunately newer printers dont carry steppers any more, those are DC motors, what you are feeling is probably the brush's contacts in the rotor.No steppers? That's interesting! What the preferred method now? Servos? Are steppers becoming phased out generation? - Scotty
Steppers are more expensive to make than DC motors, electronics is dirt cheap, so economics dictates simpler mechanicals, smarter silicon. Unfortunately DC motors wear out their brushes (stepper motors are brushless and keep going till the bearings wear out) so newer printers probably have a shorter lifetime...
enjoyaol:
Also, when I check for something which could look like a pulse encoder for a DC motor, I see that all dc motors have a special enclosure like on this picture :None of the motors in the printer look like that, that is, with a special tube that is on the right of this picture.
Edit: changed the image so that it's smaller..
That last post by mahela007 on your other thread is likely most correct - that board you have was probably (?) the pulse encoder - what was passing thru the slot? I would expect a "slotted" ribbon like was mentioned, or a slotted disk on the end of a shaft.
The picture of the encoder you posted is a more expensive industrial control - more accurate (and I think its likely a quadrature encoder - or perhaps even a binary/BCD encoder, given the number of wires). Your printer is made as cheaply as possible; its not going to have those kinds of parts in it - just whatever was made by the lowest bidder, so to speak.
I think a slotted disc was going through that. I get the disk, it's a transparent one with 4 black slots on it.
enjoyaol:
Is this 94V means they run at 94V ? That sounds crazy for such a small motor...
The 94V-0 you see on almost all PCB's has to do with how flammable the PCB substrate is (not the components attached to it)
See here: http://www.hagans.biz/pdf/ul94v012.pdf
// Per.