Re: Modular 3, 4-axis Bi-polar Chopper Driver Help

First off I would like to thank you for the thorough response;
it's great to finally find a place that people actually answer
questions. I still haven't made my mind up whether or not to
build this board; I have a couple more questions.

1.) On Steve's board schematic for the drive it says "When using
more than one board remove r10 and link c14 on additional boards."
Then right below it, it says "Also link sync pins", could someone
explain this?
2.) What is Rx1? It says it's optional and it's only required if off
board current control signal?

Thanks

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <info@t...> wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "learningcnc"
> <learningcnc@y...> wrote:
> > I want to build the 4 amp 48v driver and parallel card on Steve
> > Blackmore's website http://www.pilotltd.net/cnc.htm his design is
> > based off of Hans Wedemeyer's design http://www.hans-
w.com/cnc.htm
> >
> > 1.) Can these drivers fry my motherboard, if so what can I do to
> > prevent it?
> > 2.) What would be a good power supply?
> > 3.) Should I use a separate motor power supply for each axis?
> > 4.) Are there any design changes I should make?
> >
> > I'm not an electrical engineer and I have a lot more time then
> > money right now so any advice is much appreciated.
> >
> > Thanks
>
> 1. As Steve points out the design is not opto isolated so your PP
on
> your PC is at risk. The design assumes all grounds (motor ground,
PC
> ground, circuit ground are all common. If they are you should have
> minimal problems with fried parallel ports. If you are concerned
buy
> a cheap add-in port card and run from that. You can add a 74lS541
> octal buffer chip between the parallel port pins and the motor
drive
> circuit to give you added protection and better drive
> characteristics. It has 8 inputs and 8 outputs. It needs to share
a
> commmon ground with the PC
>
> 2. Virtually any power supply that puts out unregulated DC at the
4A
> or greater range. You can use a regulated supply, switching
supply,
> simple transformer and bridge/filter cap combo. It does not have
to
> be finely filtered or have a regulated output. There are some
> surplus 48 regulated supplies avaliable since that is a common
> voltage in the phone industry. If you do use a REGULATED supply
put
> a high current (12 to 20A) silicon rectifier in series with the
> regulated output to keep back motor EMF from raising the DC voltage
> above the regulated output and reverse biasing the pass transistors.
> Check www.mpja.com for surplus power supplies.
>
> 3. While there is nothing wrong with using separate supplies for
> each axis it is ususally more convenient to use one large supply.
> Either approach works fine. If using separate supplies they need
to
> share the same ground if using Steve's circuit.
>
> 4. I have not built Steve's circuit but others have and can offer
> advise on design changes but the design appears well thought out.
> You should consider opto isolation on any limit sensors you plan on
> using with your PC port.
>
> I AM an EE but there are many days I wished I were not and that
> computers were still just science fair projects! The feelings pass.