Re: [CAD_CAM_EDM_DRO] Interfacing EMC with Bandit drives

A UCN5804 Ic will give phase drive for the bridgeport drivers.

I make a card which has three axi converters on it for this purpose.
Connector K8 which takes the phase signals to the bridgeport drivers plugs
right onto my card, making this an easy solution to drive bridgeport mills
with other step and direction controls. You simply run wires from the step
and direction control to the input terminals for xyz step and direction
signals. You also need regulated 5 volts which is available from the
bridgeport power supply or any other source like an old PC power supply.

Tom Eldredge

----- Original Message -----
From: Jon Elson <jmelson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, April 12, 2001 1:20 AM
Subject: Re: [CAD_CAM_EDM_DRO] Interfacing EMC with Bandit drives


>
>
> Jack Ensor wrote:
>
> > The Bandit in discussion here is on a Bridgeport mill and I would
> > like to hopefully replace the control circuitry with a PC while
> > retaining the present Bandit drivers and thought that EMC may be the
> > appropriate software for this.
> >
> > The Bandit driver uses a sense resistor for sensing current and
> > controls it by varying the duty factor of the voltage pulse applied
> > to the motor windings. The control board does put out a command
> > coupled into the driver board via an opto-isolator to cut the holding
> > current in half.
> >
> > I found that the resolution is .0002 in. per step and the rapid
> > traverse is 60 ipm. This calculates out to a 5 Khz for the step
> > input. It would seem to me that the chop frequency should be several
> > times the max step frequency. I don't know why they used 5 Khz, it
> > is very noisy.
>
> Ah ha! The trick is, that when the machine is moving fast, the current
> never builds to the limit value, therefore, the switching is disabled a
> the higher feed rates. That's how they get away with the low freq.
>
> > There are 5 input signals to the Bandit driver. The position signal
> > input consists of 4 opto-isolators. A move signal is coupled to the
> > 5th opto-isolator which terminates the hold mode. After the move
> > signal is goes to zero, there is a 5 second delay via a 555 timer
> > before it reduces the current to the hold level.
> >
> > The step signal sequence into the two channels is as follows:
> > A B
> > 01 01
> > 01 10
> > 00 10
> > 10 10
> > 10 00
> > 10 01
> > 00 01
> > repeating beginning with 01 01
> >
> > Direction depends on which way you go through the above sequence.
> >
> > With this information, can EMC handle this task? If not, what other
> > software might be appropriate?
>
> Yes, for the most part, EMC can do it. EMC has been modified to generate
> phase signals like the Bridgeport BOSS drivers use. I think it is the
same
> scheme, but it looks like the Bandit half-steps, while I think the BOSS
> is full-steps, only. The code could be changed for that. But, it is VERY
> easy to convert step/direction to phase signals. There are many chips
> that can do this. I'd swear I had a drawing on my web pages of a circuit
to
> convert step/dir signals to full steps that only requires 2 chips, but I
can't
> find it now. To do half steps, it is just a tiny bit more complicated.
> Controlling the hold mode logic with a timer chip would be trivial.
>
> Jon
>
>
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