Re: [CAD_CAM_EDM_DRO] Re: Low cost - EAS microstepper driver

Hi Dave,

The allegro chip 3977 is only rated at �2.5 A, 35 V Output Rating. We actually made a board for that chip, but did not find it very rugged. There is no place for the heat to dissipate well. If you look at the LMD18245, even the chip itself is made to dissipate a lot more heat. Heat is hard on electronics. With our design you can put as big a heat sink as you want to make sure the electronics stay cool. We even use a fan just incase. Our mill, the electronics stay nice and cool. You can use those small heat sinks and fan units found in PC's and won't even notice it being warm. The chips rating is 3amps at 55volts so you have much more of a margin of error. Also it is able to take 6amp spikes, so this is a rugged chip. The allegro is a surface mount plcc chip, if you physically compare the chips side by side. I think that will decide for you.

Kin

http://www.embeddedtronics.com/


turbulatordude <davemucha@...> wrote:

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "v_fong" wrote:
>
>
> Hi Fred,
>
> We came to that conclusion when we built our drivers a while back.
> Micro stepping is really the best way if you wish to use stepper
> motors. If you are able to solder, then consider building the
> controllers. We looked everywhere at the time for an inexpensive
> micro stepper setup. We ended up building them instead and now sell
> the bare boards. I design circuit boards for a living so these
> boards are very high quality and the design has proven to be quite
> reliable.
>
> Kin
>
> http://www.embeddedtronics.com/


Hi Kin,

The LMD18245 has a manufacturers rating of 3amps and 55 volts. but
the Xylotex will smoke if someone tries to run it at the 2.5 amp and
35 volt rating.

Makes me wonder if the chip can be used at the rull rating in this
appilcation ?

As Mariss has pointed out, the back EMF can spike and kill things in
circuits unless the circuit is de-rated, or unless there is some
serious protection.

Have you tested this at it's maximum ?

I think the reason I shyed away from your unit was that the h-bridge
chips are so prices. at $26.00 for a pair for one axis drive is not
as innexpensive as us cheap bas_ _ _ds want.

Dave







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