Re: FS: New 4 axis microstepping driver $45.00 USD

Hi,
Fred wrote:

>A 24 volt ac transformer is just
> about right for a power source (plus a bridge and a capacitor).
> These transformers are readily available in 2-4 amps and contribute
> to a very inexpensive solution for a do it yourself project.

Please be aware that 24VAC when filtered and rectified becomes
about 34VDC. If the transformer were rated for 110VAC to produce
24VAC, and you used 115VAC or 120VAC (like I have), then you would
surpass the 35VDC *absolute maximum* limit of the A3977SED driver
chip. And this doesn't even include powerline surges or BackEMF into
the equation. A simple 24VAC transformer setup is probably not the
best solution for this chipset, unless the DC voltage is regulated,
or some other mods are made.
Now, an 18VAC transformer will produce about 24VDC after
rectification and filtering. Again the same powerline and BackEMF
problems must be considered, but starting at 24VDC gives much more
leeway with bacKEMF and any powerline surges that might come along.

Jeff
http://www.xylotex.com


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith" <imserv@v...>
wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, John Johnson <johnatl@m...>
> wrote:
> > Fred,
> >
> > There are several of these drivers available on the
> > internet. Can you tell us what distinguishes yours from the

others?

> >
>
> Sure, I'd be delighted to. First I have only seen 2 similar drives
> offered for sale, the Xylotex and our earlier 3 axis controller-
> driver board. There may be others, but I'm not aware of them. I
> don't know of any other A3977 board that has 4 axis. There are

some

> driver kits, but as John Stevenson mentioned these particular chips
> are difficult to solder at home. Most of the other stepper drives
> available are either more than $100 per axis, or they are
> unipolar/phase drives, and generally are limited to full or 1/2
> stepping.
>
> Next the boards do use the A3977 microstepping chips. Over the

last

> year or 2, these have been shown to be an improved solution for low
> power applications, such as desktop Sherline and Taig milling
> machines, and small CNC routers. A 24 volt ac transformer is just
> about right for a power source (plus a bridge and a capacitor).
> These transformers are readily available in 2-4 amps and contribute
> to a very inexpensive solution for a do it yourself project.
>
> The board and components cost about what we are selling them for
> (maybe even a little more). We had the components and decided that
> it was more useful to use them for a new "do-it-yourself" CNC
> product, rather than to just dump them on the component surplus
> market.
>
> We do offer support to our customers. Our user forum has specific
> discussion of the how-to, why's and wherefors associated with all

our

> products.
>
> Thanks for the chance to clarify the value of our product.
>
>
> Fred Smith - IMService
>