Re: HP plotter servo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Don" <donkiwi@y...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <davemucha@j...> wrote:
> >
> > Hi all,
> >
> > I pulled apart an old HP plotter ......
> > Has anyone ever tried to use the plotter motors ?
> > > Has anyone ever hacked the controller board for these for CNC
> use ?
> > Any ideas what to do with them ?
> > Since I have three more plotters I'm not sure if I should pull

them

> > apart for parts or just junk them.
> >
> > Dave.
>
> Dave,
> This is the idea that gave me the CNC bug many moons ago.
> I still haven't shaken it and a relapse was brought on recently

with

> the imminent delivery of a free HP 7475A Graphics Plotter. I

already

> received the (Operator's) Manual.
> Hopefully, the motors in mine are steppers, for simplicity.
> To keep things simple, I will use the output motor phase signals

and

> add a simple Driver Stage (eg. Higher Voltage stage with 4x
> darlingtons to bigger steppers). I intend to stick with the HPGL

and

> drive it as a Plotter as designed.
> The original cheap Plotter that I first played with was on a SHARP
> MZ700 64kB computer circa 1978. It had 4 wee coloured ballpoint

pens

> in a rotating chamber. Motors were driven by 5V TTL Hi levels on

the

> phase wires!
> A BASIC command such as "CIRCLE 5,46,0,360,0.2" (Draw a circle with
> centre at X=5,Y=46, Radius:123,Start Angle:0,End Angle:360,Step
> Angle:0.2 degrees) involved sending ASCII codes
>

for "C","comma","5","comma","4","6","comma","0","comma","3","6","0","c

> omma","0",".","2" to an onboard interpreter).
> HPGL may well be interpreted onboard in vintage plotters in a

similar

> way. Axis co-ordination being done onboard.(A reason to stick with
> that command format.)
> There are a few different ways of achieving extra controls. Pen-
> Up /Down is readily available (including successive Pen-Dns!)and

the

> pen change movements can be modified also. (The SHARP simply drove
> the pen carousel against an off-plot-area stop with the pen up.

Each

> motion against the stop indexed the carousel to the next pen by a
> simple mechanical ratchet.)
> Pen cleaning movement routines are often available for playing

with,

> too.
> I scrapped the SHARP project because it only addressed -480 to +480
> clicks on X-axis. HP7475A does -32767 to +32767 clicks per axis, so
> 32" at 0.001" resolution is possible!
> Don't throw those boards out yet! They may be smarter than you

think.

> (Or throw them my way.)
> Anyone wanting to share manuals/info/hardware/ideas on plotters,
> please keep in touch. Hurry, though, because I just ordered a 4

axis

> Xylotex Driver, and am in danger of going mainstream unless
> encouraged. :)
>
> Cheers, Don.
>
> P.S. Photos will be forthcoming, Dave, but I don't seem able to

post

> to Files area ....

Does your manual have schematics ?

It may be possible that the boards are similar. I can get you
numbers off the boards.

I am going to put them on E-bay if I can't get someone to get me a
schematic or trace out the connections. For the $35 bux or so for
the 4 I have left I can buy a Xylotex and use my steppers.


as for posting pictures, the files area is closed to public posting.
unfortunatly, it got filled and no one deleted stuff.

There are a few other yahoo groups you can post, one is

http://groups.yahoo.com/group/CNC-pics

Or send them to me and I'll post them.

Dave