Re: [CAD_CAM_EDM_DRO] Re: FS: New 4 axis microstepping driver $45.00 USD

Ref the over volt question, i bought a 2x12v 9.37amp toriodal transformer
from Maplins, this when rectified gives me 36v on 24v input which is too
much for my hobbycnc board so i just used the 12v, it still gives me a
healthy
28v without load (post rectification) which is more than enough for the
chips and keeps me happily within limits in case of spikes etc.

Nick

----- Original Message -----
From: "jt4897" <johnt@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, March 20, 2004 4:23 AM
Subject: [CAD_CAM_EDM_DRO] Re: FS: New 4 axis microstepping driver $45.00
USD


> I think in this case it is not simply about exceeding the
> manufacturers limits but rather that we are talking about
> home built power supplies and that for the Allegro chip
> 35V cannot be exceeded. I think that Jeff can attest to
> that as an expert.
>
> My power is quite good and my provider (Hydro Quebec) says
> that for a normal 120V supply the voltage can vary between
> 106V and 127V (marginal) and that normal would be between
> 110V and 125V.
>
> Doing some math we can see that at 24VAC x 1.414 = 33.936VDC
> But that would be based on 120VAC in - what happens when
> it jumps to 127VAC? My DC could jump to 35.9156. That's
> about 1VDC more than it takes to blow the drive and yet we
> are still within the acceptable limits of service. Now
> add back EMF.
>
> Personally I'm running a 22VAC transformer and I feel like
> I've pushed the limit (aprox. 32VDC). I think Jeff
> recommends 30VDC as a limit.
>
> There is a circuit around somewhere from Mariss (of Gecko)
> that shunts overvoltage to ground. Great! But most
> users of these drives are probably like me and haven't
> built it. :-( Most of us want to snap the pieces
> together and go, safer to recommend 18VAC or 24VDC and
> leave the limits to those that are more daring.
>
>
> -John
>
> PS: Some UPSs allow you to set out voltage but many
> cheaper UPSs I wouldn't trust to hold it 120V.
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith" <imserv@v...>
> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "jeffalanp" <xylotex@h...>
> > wrote:
> > > 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.
> >
> > Jeff,
> >
> > I agree whole heartedly. If local line voltage exceeds 120, it is
> > probably a good idea to consider a step down transformer for any
> CNC
> > equipment, this is very common practice on commercial machinery. I
> > would also recommend a UPS type setup on your computers as a UPS
> will
> > usually have some voltage regulation to maintain supply voltage
> > within a narrow range. Surge protectors at a minimum.
> >
> > It's a good idea not to exceed the manufacturers limits on any
> > electrical equipment.
> >
> > > On Wednesday, Mar 17, 2004, at 17:40 US/Eastern, Fred Smith wrote:
> > > >> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith"
> > <imserv@v... wrote:
> > > >>>> We have a limited edition, 4 axis, microstepping driver
> > available.Based
> > > >>> on
> > > >>>> the Allegro A3977 chip. The board is rated at 2 amps per axis
> > > > and
> > > >>>> maximum of 35vdc. This is a promotional item and is subject
> to
> > > >>> prior
> > > >>>> sale. Quantities are very limited.
> > > >
> > > > Info at: http://www.cadcamcadcam.com
>
>
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...,
timg@...
> Moderator: pentam@... indigo_red@... davemucha@...
[Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>
>
>