Why does a dc motor "stutter"

[jackyson]

I have a 12v motor, scavenged from an inkjet printer (there isn't a model # on the motor). I have a pulley set up on the motor, that moves a load of about 375 grams. When I connect the motor to 12v, the pulley "jumps"(like a stepper motor) about a mm or so, but then stops, and wont move any more until it is disconnected and then reconnected to 12v. Why is this happening? I wasn't expecting this to happen, but actually I am building a small scale cnc, so this is actually pretty useful. The only thing is, I need a way to make this more precise, so that I can tell how much the motor moves each "jump". I would also like to know, if it is possible, how to make the motor run continuously, without stuttering.

 

[Minder]

It shouldn't, what is the exact nature of the motor?
Sounds more like a stepper motor, if anything?
The CNC system would need to be pretty small if it is a stepper of that size, which they often are from prointers etc.
M.

 

[kellys_eye]

How many wires come from the motor? If it's more than 2 then it's as @Minder suggests, a stepper motor.

If there are only two - and some printers use normal motors mounted with slotted opto-couplers - then the motor could just be stalling under load and may require reduction gearing to increase torque.

 

[BobK]

Does it run continuously when not loaded? If not it likely is a stepper, or a brushless DC motor that requires external electronics to run it. A picture might be useful.

Bob

 

[Bryan McMullan]

I'd be willing to bet it's your power supply overheating or something.

 

[duke37]

I have never used stepper motor but this sounds as if it is one.
You can probably find the steps/turn by energising one winding with a steady current and counting the number of 'cogs'.

 

[Minder]

.
You can probably find the steps/turn by energising one winding with a steady current and counting the number of 'cogs'.

Can also be done by simply shorting the winding's and spinning the shaft.
M.