Re: Camtronics 5A Stepper Motor Driver Board - Power Supply Current Requirements?

----- Original Message -----

> From: "Matt Shaver" <mshaver@...>
> Question:
>
> The instructions that come with the board lists one of the specifications
> as ".5-5 Amp Output Per Phase With Two Phase On". If I were to adjust the
> drive current to 5 amps for all three motors, and all three motors were
> stopped at a half step position, would the total current draw be 30 Amps
> (5A drive current x 2 phases on x 3 motors)? Some links I looked at to
> understand steppers and half stepping mode:
>

That is a good question and I don't know the real answer. From my
experience the input current draw is less than the total of what each axis
is set for added together (3 axis's set at 5 amp each draws less than 15
amp). On my power supply I have a number of seperate circuits with
individual breakers. When I was running 3 axis's at 2 amp each and was
connected to a 3 amp breaker I would pop the breaker occasionally. I am now
running 2 axis's at 4.92 amps (all I can get the controller to go up to) and
the 3rd at 4 amps and it is all conected to a 7 amp breaker and I have never
tripped it. I sort of asked Dan about this in determining what value to use
for a particular motor and despite his best efforts I am not sure if I
understand, but basically the draw is less than the amount the axis is set
for as the chopper circuit turns the current on and off so if you are set at
5 amps it is not a continious 5 amp draw, but a momentary 5 amps then 0 then
5 amps then 0 . . . . . . The result is the power supply sees a draw
less than the combine total setting as the 3 axis's are not all on at the
same moment.

> I'm hoping to use this board to drive the original stepper motors on an

old

> Bridgeport BOSS4 mill. These are really large motors made by Superior and
> also Sigma. I was wondering if any one knew what the correct drive current
> was for these. In the maintenance manual they talk about adjusting the
> current to 8 Amps, but the original drive circuit was the RL type and the
> Camtronics board is a chopper.

I set the motors to 75% of their rated current when using uni-polar motors
in bi-polar mode. This seems to jive with what I have seen when both motor
ratings are given.

Tim
[Denver, CO]