Homebrew PCBs

Hi all,

I am lucky enough to have gotten a few HP plotters.  these are the 
ones with the multi pen carosel.  I need to check each to see if they 
are all the same model.   The paper moves back and forth under the 
pen and the pen moves side to side.

Anyway, I am thinking of doing something with them.  one idea is to 
unload them on E-bay, another to see what steppers are used.

the last is to modify one for making PCBs.

the connectors are GPIB or some such odd type.

any suggestions ?

in reading the list there is the pen filled with resist idea and the 
coat the board and scratch off the coating idea.

has anyone modified one of these for drilling ?

Dave

have similar.
steppers not too much interesting i think.

mine has rs232.
gpib may be hart to interface, no idea what io cards cost.

did not try drilling.

regards
st

I used to use an hp 7475A plotter for pcbs and I found it difficult 
to get good results. It is very hard to plot double sided pcbs. Even 
if you get that to work, you still need special pens that are 
resistant to etchants. I decided to look on Ebay for an Okidata Laser 
Printer and print to Jet Print Photo Graphic Image Paper. I haven't 
looked back since. Genaro

GPIB interface cards are -very- expensive, $300 ISA and $400 PCI, same
price new or used.

However, a GPIB plotter may fetch a good price on eBay, as long as you
emphasize that it is GPIB. There are still a lot of places using it on
test equipment and plotters.

I mistakenly picked up a GPIB plotter (HP 7475a) at Boeing Surplus for
$20, then after finding out the price of the interface cards I sold it
on eBay for $75. To a business less than 2 miles from Boeing Surplus!

Have you checked out the Scratch 'N Etch idea for making PCBs? There
are some sample etches in the Files (or maybe photos) section.

They are not strong enough to use for drilling. You'd have to rebuild
them entirely, only using the electronics/firmware to drive larger
steppers and more robust mechanicals. Might as well build it from scratch.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" <dave_mucha@y...>
wrote:

> Hi all,
> 
> I am lucky enough to have gotten a few HP plotters.  these are the 
> ones with the multi pen carosel.  I need to check each to see if they 
> are all the same model.   The paper moves back and forth under the 
> pen and the pen moves side to side.
> 
> Anyway, I am thinking of doing something with them.  one idea is to 
> unload them on E-bay, another to see what steppers are used.
> 
> the last is to modify one for making PCBs.
> 
> the connectors are GPIB or some such odd type.
> 
> any suggestions ?
> 
> in reading the list there is the pen filled with resist idea and the 
> coat the board and scratch off the coating idea.
> 
> has anyone modified one of these for drilling ?
> 
> Dave

--- In Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@y...> 
wrote:
> GPIB interface cards are -very- expensive, $300 ISA and $400 PCI, 
same
> price new or used.
> 
> However, a GPIB plotter may fetch a good price on eBay, as long as 
you
> emphasize that it is GPIB. There are still a lot of places using it 
on
> test equipment and plotters.
> 
> I mistakenly picked up a GPIB plotter (HP 7475a) at Boeing Surplus 
for
> $20, then after finding out the price of the interface cards I sold 
it
> on eBay for $75. To a business less than 2 miles from Boeing 
Surplus!
> 
> Have you checked out the Scratch 'N Etch idea for making PCBs? There
> are some sample etches in the Files (or maybe photos) section.
> 
> They are not strong enough to use for drilling. You'd have to 
rebuild
> them entirely, only using the electronics/firmware to drive larger
> steppers and more robust mechanicals. Might as well build it from 
scratch.
> 
> Steve Greenfield

Darn,

I guess I may pull one apart for parts and see what the others bring 
on e-bay.

I am surprised no one figured out some better way to work them.

Being a moving paper unit, I can see the limitations.

I'd like to make a simple pcb drilling unit out of one, but if the 
gantry is not strong enough, which was only designed for a pen, I 
need to do something else with them.

I gave one to a friend who made a cable and then used it for plotting 
his cad drawings.  he is happy with it.  He  said hte HP-IB and GPIB 
were the same.

Dave

In a message dated 7/18/2003 9:49:58 AM Central Standard Time, 
dave_mucha@... writes:

> another to see what steppers are used.
> 

That plotter has servos with encoders!  Whiz-bang thang, it is!  Too compex 
for ignoramouses like me, so I sold mine for $50 + shipping!  %-wise, one of my 
best-ever deals!  Original cost:  $0.00 ! ! !


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 7/18/2003 9:49:58 AM Central Standard Time, 
> dave_mucha@y... writes:
> 
> > another to see what steppers are used.
> > 
> 
> That plotter has servos with encoders!  Whiz-bang thang, it is!  
Too compex 
> for ignoramouses like me, so I sold mine for $50 + shipping!  %-
wise, one of my 
> best-ever deals!  Original cost:  $0.00 ! ! !
> 
> 
> [Non-text portions of this message have been removed]


If it has encoders then it is pretty valuable.  at least to me.
it would be a great start for a pcb driller.  encoders help make the 
unit more accurate than steppers.

even without the encoders, the DC servo motors can be used as a 
drilling head.

I guess when I pull it apart, I'll find out !


Dave

if it is anything like the one I tore into the "encoders" may surprise you
on that one they were an odd type with raised spiral magnetic arms 
spinning over opposite spiraling traces on the pickup board with a
daughter card to convert the signals 
nothing like the slotted disk optical encoders I was expecting

you might be able to use the motors with the original main board and
build a stronger gantry to hold the drill rig ,HP claims a resolution of 
1/40th mm on those plotters but the motors aren't any bigger than they 
need to be to move the original parts (paper and pen holder)
maybe if you use a belt reduction to get more torque and scale up
the HPGL output to get it back to the right size?


Brian
-- 
"Nemo me impune lacesset"

> > That plotter has servos with encoders!  Whiz-bang thang, it is!

> If it has encoders then it is pretty valuable.  at least to me.
> it would be a great start for a pcb driller.  encoders help make the
> unit more accurate than steppers.
>
> even without the encoders, the DC servo motors can be used as a
> drilling head.
>
> I guess when I pull it apart, I'll find out !
>
>
> Dave

On Sat, 19 Jul 2003 11:46:41 -0700, Brian Pitt <bfp@...> wrote:

> if it is anything like the one I tore into the "encoders" may surprise 
> you
> on that one they were an odd type with raised spiral magnetic arms 
> spinning over opposite spiraling traces on the pickup board with a
> daughter card to convert the signals nothing like the slotted disk 
> optical encoders I was expecting
>
> you might be able to use the motors with the original main board and
> build a stronger gantry to hold the drill rig ,HP claims a resolution of 
> 1/40th mm on those plotters but the motors aren't any bigger than they 
> need to be to move the original parts (paper and pen holder)
> maybe if you use a belt reduction to get more torque and scale up
> the HPGL output to get it back to the right size?
>
>
> Brian

but maybe then it is much easier to use one of the free designs on the web, 
which use steppers.
some use very simple stepper controller circuits on lpt.

if interested in stepper control please read "control of stepping motors, 
david jones, university of
iowa, dept. of computer science." this document you can easily find with 
google.
i like it. shows control circuit optins and also copes "how to increase 
performance/speed" issue...

but i like the 7475a plotters and i would keep one if you can interface it.
you can use it for other things (like plotting aerofoil shapes for making 
foam wings for rc plane).
it is also one of the old good things from hp, before they changed from 
"product orientated" to "consumer orientated".
before charly came etc..


i don't believe this servos can be run at 20000rpm or so. so use as i 
spindle is not good i think.+


regards
stefan