Thursday, 22 March 2018

Re: [7x12minilathe] Re: Mini-Mill CNC, First Test of X-Axis.

 

Those 6 and 8 wire motors have 6 or 8 wires for a reason.   If gives the user a choice.    

All motor have two coils.   If they run the ends of the coils out of the motor there are four leads (as each coil has two ends) this is the normal case.

But what if you place a center tap in each coil?  Now you have six leads.   Why one Earth make a center tap?   It gives the user a choice 
(a) he can ignore the center tap and even cut the wire off and have a four lead motor or
(b) he can use only 1/2 of the coil feeding power from the center to one end.  Of course this makes the motor half as powerful but it can also rotate faster with coils that have much less inductance
(c) there are other options but they don't apply unless you are designing your own motor driver which is a specialist engineering job.

With 8 lead motor they go one step farther.  Rather then center tapping each coil they cut it in half now you have three options.
(a) connect the cut coils back together and make a normal four lead motor
(b) use just one of the half coils (not a great option because as in "b" above the motor is only 1/2 as powerful.
(c) use both half coils in PARALLEL.   This is a very attractive option as it greatly reduces the coil inductance as in "b" but lets you use all of the motor's designed power.

If yu download the PDF manual for the driver it explains this.  

But in ALL of the above cases the driver sees only four leads because you have connected them, cut them off or whatever before connecting to the driver.   So in effect all motors have only four leads

Most motors have 4 leads but if you have an 8 lead more




On Thu, Mar 22, 2018 at 4:53 AM, Tim Iafolla iafollatim@yahoo.com [7x12minilathe] <7x12minilathe@yahoogroups.com> wrote:
 

I'll just add one thing to Chris's excellent explanation: modern stepper drivers have 4 motor output pins (usually labeled A+, A-, B+, and B-), but stepper motors will have 4, 6, or 8 input wires. 


If your motor has >4 wires you'll need a multimeter to figure out which of the 4 wires to connect. There are YouTube videos showing how to do this, but basically you're trying to find the 2 pairs of wires with the lowest impedance between them—those are your A and B pairs.  The other wires can just be twisted together in impedance-matched pairs.  

Tim

Sent from my iPhone

On Mar 21, 2018, at 10:32 PM, Chris Albertson albertson.chris@gmail.com [7x12minilathe] <7x12minilathe@yahoogroups.com> wrote:

 

When you work with stepper motors you don't actually interface to the motor.   You interface to the driver.   The driver connects to both your power supply and to the motor.   The driver is so simple you don't need a drawing as there are just two interface pins

1) "step" the leading edge of a pulse will cause the motor to move one "step".  typically a about 0.9 degrees or less.  These are switches on the drive that set the step size.
2) "direction" this pin is either high (5 volts) or low (grounded) and determines in which way the motor steps CW or CCW.

That's it.  two pins..   If you want the motor to rotate at 60 RPM then you send step pulses at (say) 400 pulses per second.  The motor stops when you send no pulses.

Given that you are using a modern driver,  the above is all you need to know.




On Wed, Mar 21, 2018 at 6:26 PM, 'Johannes' johannes@lavoll.no [7x12minilathe] <7x12minilathe@yahoogroups.com> wrote:
 

Hi Mark

I have worked with 555, but not with stepper motor, can you give us a drawing ?

/johannes

Fra: 7x12minilathe@yahoogroups.com [mailto:7x12minilathe@yahoogroups.com]
Sendt: 21. mars 2018 10:52
Til: 7x12minilathe@yahoogroups.com
Emne: Re: [7x12minilathe] Re: Mini-Mill CNC, First Test of X-Axis.

RE: pulser for simple stepper control. I made one for zero dollars -- I already had a 555 timer chip, and my electronics scrap box had the perf board, resistors and capacitors I needed to make a simple clock generator. A slide switch allows me to select the direction, and I can adjust the clock rate with a pot.

I used the thing to run a stepper as a low-speed diamond grinder for shaping and sharpening carbide scrapers. I bought a set of 6" diamond lapping disks from a lapidary supply outfit, 150 grit up to 3,000. The low speed keeps everything cool (particularly since I run the bottom portion of the disk through a pool of water). It does a good job for me. I made a simple arbor to mount the disks using my lathe.

The ebay pulse generator looks like a good value if you're not able or willing to DIY one.

Mark

 [Non-text portions of this message have been removed]




--

Chris Albertson
Redondo Beach, California




--

Chris Albertson
Redondo Beach, California

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