Re: [CAD_CAM_EDM_DRO] Re: testing with multi-meter - GECKO

On Sun, 20 Apr 2003 20:22:40 -0000, you wrote:

>"turbulatordude" <davemucha@j...> wrote:
>
>> if you have a line on the pin 7 shut-down, pull it off and re-test.
>
>Sigh!!!! This will involve some work as the screw terminals are not
>directly accessible.
>
>BTW, in plain words, what is the advantage of connecting terminal 7?
>The Gecko will work fine without bothering to connect terminal 7
>
>BTW2. This is a separate problem, but had connected one motor cable
>wrongly (but which is not the cause of the original problem - x-axis
>silent). Taking the Gecko output terminals as A-A'(phase A) and B,B'
>(phase B) this faulty cable was wired such that one coil is connected
>to A-B and A'-B'. I expect that this will produce silence at the
>motor, but no, it produced violent vibrations at the motor. WHY?

The phase sequence was way off.

Given a stepper with 4 poles, you want to have the stepper phase
sequence 1, 2, 3, 4. The reason that it goes from any one position to
the next, say 2 to 3, is that the magnetic fields are more
"attractive" (pun intended) to the rotor....

Wiring the phases backwards, say that you have a stepper connected so
that the resulting sequence is 1, 3, 2, 4 will give you that sequence,
maybe... However, getting the sequence really wrong can produce a
situation where a backwards movement is more attractive than a
forwards movement (done that when playing with unknown steppers).

So you have a forwards movement, 1, 2, 4, 3 and from 3, it's equally
good to go back to 1, since the whole thing repeats...

1, 2, 4, 3, 1, 2, 4, 3 However, that 1 position (and there are many
of them, is not the next 1 position, it's the previous one....

let me explain a bit, the motor only has 4 electrical poles, but they
are arranged in sequence around the motor... so they look like

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

If you are at pole 3, then you can go to pole 4 because pole 4 is more
attractive, 3 is off, and 2 might be repelling you....

However, miswiring the motor can cause you to jump to 3 from 1, then
back to 2, then if you switch 4 on, you can easily go to the back
direction 4... This will happen especially if there is a load on the
motor. Only by having the rotor go to 1, 2, 3, 4, 1, etc... in
sequence, will the motor really turn...

Hope that makes sense.

Harvey

>
>Thank Dave, others
>
>Andrew
>
>
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