RE: [CAD_CAM_EDM_DRO] Re: Don't give up!!!

Ok, so I made a mistake! Use the MPJA 7843 TR transformer for 18 volts at 2
amps and you wind up with about 24 to 25 volts DC and save money, since the
7843 TR transformer is only $4.63, a savings of $13.36. You can also change
the capacitor to the Mouser 539-CGS35V12000 for $9.46, a savings of $20.20.
This brings the hardware cost to $166.79 and the total including TurboCNC to
$186.79 which is a real bargain for CNC in today's hobby market.

Add this to a Sherline mill or a Taig CNC ready mill and you have a real
nice beginner CNC system for around $1000.00, not bad by current standards.
In fact, that seems like a system that would serve well in any small shop
for a long time. If you already have the mill you can make your own motor
mounts and be up and running quite quickly.

John Guenther
'Ye Olde Pen Maker'
Sterling, Virginia

> -----Original Message-----
> From: jeffalanp <xylotex@...> [mailto:xylotex@...]
> Sent: Friday, January 31, 2003 13:32 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Don't give up!!!
>
>
> Hello,
> Please be aware that a 24VAC transformer, when rectified and
> filtered is going to give about 34VDC. This is dangerously close to
> the 35V maximum rating of the driver chip I use on the stepper driver
> mentioned in the posting listed below (and BEMF hasn't even been
> taken into account yet). Allegro Micro. (mfg. of the A3977SED used
> on the board) suggests a maximum running voltage of no more than 90%
> of the 35V maximum (or about 30V). If the transformer was rated at
> 110V, and you used 115 or 120V instead, you'd more than likely exceed
> the rating of the chips. Unless a regenerative (returned energy)
> dumping circuit is used to keep the voltage below 35V, you may have
> problems running so close to the maximum (or just plain blow things
> up!)
>
> Thanks,
>
> Jeff
> http://www.xylotex.com
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "j.guenther"
> <j.guenther@v...> wrote:
> > Amen, and you can now get a very workable CNC conversion of a small
> machine,
> > for about $225.00 not including the machine. I have the plans for
> Dave
> > Rigotti's HobbyCNC machine and have seen one in action that someone
> in the
> > CAMS club built, pretty impressive for a plywood machine, and the
> quality of
> > the work he produces with it is outstanding. Below is my take on
> just how
> > low cost you can go for a basic beginner CNC conversion:
> >
> > Estimated Cost of a Basic CNC Conversion
> >
> > Supplier Part Number Price
> > Xylotex Driver Board
> > www.xylotex.com Xylotex XS-3525/8S-3 $85.00
> >
> > 24 Volt 10 Amp transformer
> > www.mpja.com MPJA 7846 TR $17.99
> >
> > Bridge Rectifier
> > www.mpja.com MPJA 5248BR $2.70
> >
> > 15000uf 100 V Electrolytic Cap
> > www.mouser.com Mouser 539-CGS100V15000 $29.66
> >
> > 3ea 100 oz/in Stepper Motors e-bay $25.00
> > Misc. wire, switches, connectors Radio Shack $40.00
> >
> > Electronic Parts: $200.35
> >
> > TurboCNC software www.dakeng.com DAK Eng. $20.00
> >
> > Total: $220.35
> >
> >
> > Please note that this does not include shipping, motor mounts, motor
> > couplers or a box to put the driver / power supply in. Depending
> on the
> > current levels you are using you may also need a fan for the driver
> box. I
> > did not include the cost of a surplus PC since this can vary
> greatly. This
> > also does not take into account what a person may already have in
> their
> > parts collection.
> >
> > John Guenther
> > 'Ye Olde Pen Maker'
> > Sterling, Virginia
> >
>
>
>
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