>
>
> HEY......
>
> That's not nice!....
> I know that developing take time...
> But EMC programmers doesn't charge for many hours they 'wasted'. ... and
> support and... ... ..
> If you have enougth money to buy $7000 machine then there is stupid
> think to save $97 here...
> But if you check what is most popular EMC2 usage then you (surprising)
> find out that the most is used on small bench mill's. And I think that
> mill's are homemade build and they are cheap. And over that $97 can be
> big amount to pay.
> So there are many builder wanted to make personal small mill with at low
> budget. If there are someone that start to earn money with own CNC then
> they soon realize that 'old one' is to slow, to unpresise, wear so
> fast.... and wil make or buy better one.
> So please make difference betwen hobby users and serious biznis use. The
> only EMC2 is cheap (free) for both.
>
> And I didn't say that Hardware need to be free! Just some PROVEN schematic.
> As I find no good EPP expander I just drawing one and wan't to do that.
> And schematic will be free.
>
>
>
> ... and I live in Earth. (still :D)
>
>
So I use EMC for hobby stuff here at home. I have also used EMC for business
use in R&D machines and I have been very happy with it. When I first stared
using EMC when I was a freshman in college I didn't want to spend any money
buying other people's hardware, I just wanted to make my own to "save
money".
The first machine that I made was a servo machine so I made a step/direction
input closed loop servo controller from scratch using FETS and an AVR
microcontroller. At the time I thought that I was saving money by making my
own board because the parts for each board (single axis) only cost like $17
or something like that. But I had a 4 axis machine so just hardware cost my
like $68 and the quality of my board was not that great.
Then lets consider how much time I spent neglecting my engineering homework
to build the boards, I think it had to be more that 10 hours for each board,
lets say that I don't value my hobby time much and it is only worth about $2
and hour (I value my hobby time much more than that now). So it cost me
about $80 of my time as a very conservative estimate (How much did I spend
on tuition that semester? and I'm neglecting my homework). So now I'm into
this project $143 and it works ok but feels very home grown. And after all
this doesn't include all the equipment that I purchased to make the boards
for the original development board. I spent lots of time hooking a serial
cable up to my servo drives to tune them through a TTY interface.
Lets fast forward to a couple of years ago. At this time I was a graduate
student and still broke. I was building a new machine and thought that I
could save some time by purchasing some off the self components. I never
really analyzed the cost of hardware on my previous project, I just thought
that I could make the hardware for so much less than buying it. I discovered
the 7i43 ($79) and the 7i30-4($89) boards from Mesa Electronics. So for
$168 I purchased an off the shelf 4 axis closed loop servo system with 24
additional I/O points. I couldn't believe how affordable this solution was.
I was even more blown away after I got the boards and stared using them. I
hooked the boards up to my old machine and I couldn't believe the improved
performance over my DIY drivers. For any new machine I make, hobby or work,
I will use off the self hardware to save time and money.
Now if I had could go back and do it all again I would still make my own
hardware the first time because I learned so very much from doing it but I
have to admit that I wouldn't have saved any money. So if your argument is
about saving DIYers money then forget about it, because in my experience it
open source boards don't do that. However I agree that you learn a whole lot
from building your own hardware.
I would suggest that people who are trying to just bodge together a quick
low cost machine just use stepper motors and the parallel port. If you need
more I/O points then add a PCI parallel port card to your computer (I know
that requires you to have used a computer with open expansion ports, one
reason why I would never use a laptop for EMC). Another option for
non-real-time I/O and functions is to use and Arduino board connected to the
USB port. Take a look at http://axis.unpy.net/01198525592. That whole
solution is completely open source and you can do what ever you want with
it, it will be fast, but just not hard RT.
If you want to build some hardware just for the fun of it and to learn
something then I suggest looking at the wiki here:0
http://wiki.linuxcnc.org/emcinfo.pl?EMC2_Supported_Hardware under the
heading "DIY hardware known to work with EMC". There you will find some info
on the Pluto FPGA setup, an opensource FPGA based solution for EMC. You
should be able to build your own board with the info from that project, but
I wouldn't suggest doing that if you don't have lots of time and money to
trow at it. If you end up doing that please share your results.
But as far as the parallel port expander goes, the most common solution is
simply to add another parallel port to that machine. If you don't have an
expansion port in you computer you may want to reconsider you choice of what
computer to use. Please consider that a parallel port expander would require
an new driver to be written and maintained. The driver is problably a much
bigger challenge that the expansion board.
Sorry if you have made it is far sorry that I have rambled on forever on a
list that I don't really have any business posting on. I have probably
violated some written and unwritten rules of the list, sorry for my
ignorance.
Slavko good luck with your project.
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