Homebrew PCBs

Hi Robert,

Thanks for the encouragement. Yes, I looking for a "rinky dink" 
system. It fits my basic needs.

Thanks for the link, on the stepper driver. I had seen it previously 
and that is what got me thinking that the 8 pin PICAXE with 5 i/o's 
might do the job. I understood from that write up, that for single 
stepping it took just 4 2 bit numbers along with a couple of 
inverters.

For single stepping the two lines can be used for each of the 
motors. By adding an inverter to these lines you get the 4 lines 
needed for the steppers. Since for single stepping they always are 
inverted.

The PICAXE website has schematics for this type of circuit. It uses 
a 2003 or 2803 for the low power drivers, with the spare gates used 
as inverters. It also has the short program to output the 2 bit 
pattern to drive the steppers in single step mod.

The 8 pin 3 dolalar picaxe could work for a small number of holes, 
fur to its limited memory. But the 18 pin 18X version (about 10 
bucks) has more memory and enough i/o pin to drive all 8 lines, thus 
voiding the need for the inverters.

The key here is the simplicity and light framework needed, thus the 
low cost. The trade offs include preplanning the layout and loading 
the coordinates into the Picaxe program before downloading. But once 
its done, you have permanent drill file.

Bu using one i/o line for start, goto next hole, a pc is not needed 
to run the program. the PICAXE would be all that is necessary. For 3 
bucks, yo could keep each drill program on a chip and change chips 
when needed.

There would be some initial calculations to get the stepper's 
rotation converteed to linear values, but I don't think that shuld 
be too bad.

Thanks again,

Myc




--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan 
<robert.hedan@v...> wrote:
> 1st: if Eagle doesn't produce a DRILL file, chuck it, I can't 
remember if it
> does.
> 
> 2nd: if you are going to go into programming, might as well follow 
the
> conventional technique using steppers, that way you can copy 
existing code,
> same thing for the stepper motor control circuits.
> 
> 3rd: you can use the same technique as the others, but drastically 
reduce in
> size everything, that in itself will make a LOT of things easier, 
for
> example, a 12" rod of aluminium 1/4" thick will be plenty for 
you.  Same
> thing with the screw, a 1/4" diameter screw would be fine.
> 
> 4th: make it all out of wood, REAL easy to cut & drill, using 
holes in the
> wood as bushings for the rods.
> 
> 5th: polish the aluminium rods slightly, just to give them that 
extra shine,
> which translates into less friction (maybe a little dab of 
lubricant).
> 
> 
> Myc, I've looked at a lot of ways to skin this chicken, and if you 
have a
> DRILL file, can program PICs, can download the file, can assemble 
a basic
> stepper controller like this one:
> <http://www.xavierkamial.com/Videos/Stepper%20Motor%
20Controller.htm>, then
> steppers are the way to go.
> 
> Everything is out there for a rinky-dink system, I am just looking 
for
> something with a little more ooomph.  But for drilling, el-cheapo 
steppers
> cost no more than $5.  Using servos, you'd be all alone in left 
field, with
> probably no samples from the web to get ideas from.  With 
steppers, you'd
> get pretty darn close to the same precision as a lot of us will 
get.  The
> only difference is that we will be able to maintain that precision 
over a
> longer surface; which you don't need anyways.
> 
> Robert
> :)
> 
> 
> 
> -----Message d'origine-----
> De : Homebrew_PCBs@yahoogroups.com 
[mailto:Homebrew_PCBs@yahoogroups.com] De
> la part de mycroft2152
> Envoyé : juin 11 2005 20:10
> À : Homebrew_PCBs@yahoogroups.com
> Objet : [Homebrew_PCBs] PCB Driller - Looking for comments
> 
> 
> Hi Guys,
> 
> I've been following the pcb driller discussion. I've been wanting 
to 
> build one for a long time. But so far the designs seem too 
complicated 
> or too heavy duty for my needs. And too expensive too. I want to 
throw 
> out a couple of ideas. I'd appreciate any thoughts on them. (Yes, 
> Stefan, I wouldd like yur thoughts too, as long as they don't 
include 
> anything about a chicken grill. :)
> 
> I use EAGLE free version for my boards. That means they are under 
3" x 
> 4". When drawing the layout, I set EAGLE at a 0.10" grid 
(sometimes I 
> cheat and go  0.05"). I lay out my components to fit this grid. 
This 
> works well, but I don't like to manually postion the board for 
driling 
> on my drill press.
> 
> It occurred to me that what I needed was something that could 
drill 
> holes on a 3" x 4" grid. At 0.10" spacing the grid would be 30 by 
40, 
> and on 0.05" spacing the grid would be 60 x 80.
> 
> I will say, for now, I am not interested in milling, just drilling 
> holes. And I would be willing to "pull the handle" on the drill 
press. 
> My boards are small enough with not too many holes. So what would 
it 
> take to build a grid based driller.
> 
> My first thought was converting an old printer. Attaching a small 
> dremel to the print head. I would move the print head across the 
page 
> stoping at the appropriate spot and the pulls the handle. Afte all 
the 
> holes on one line were drilled, go to the next line. After all if 
you 
> cn print a grid of dots on a page, you could move the print heaad 
with 
> simple commands.
> 
> The second idea I had, after looking at all the drivers chps and 
> software and discussion about half stepping and choppers, was that 
the 
> driller could be very light duty due to the size of the board and 
the 
> coarseness of the steps.
> 
> Looking at the old Nasa stepper design, that uses 2 flip flops and 
a 
> couple of nor gates, I realized that 2 lines would be all that i 
> really need for single stepping.
> 
> I've been playing woth the PICAXE chips. They are programmed in 
basic 
> and only need a 3 wire cable for programming. Best of all they 
(the 
> 08M)are only about $3 each, and has 5 i/o lines.
> 
> I've been thinking about using one of these as the controller. If 
I 
> download the coordinate of the holes, program, The PICAXE could 
> convert the coordinates to steps I could position the drill using 
just 
> 4 of the 5 lines. The 5th line would be an input to start or go to 
the 
> next holes. A driver chip or transistors would be needed for the 
power 
> to run the servovs. 
> 
> For the driller bed, a light duty X-Y table about 6" x 6" could be 
> driven by some small servos and screws.
> 
> It would be a small, inexpensive, semi automatic pcb driller.
> 
> What do you see as the pitfalls with these two ideas?
> 
> Myc
> 
> 
> 
> 
> 
> 
> 
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> 
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