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
>