Homebrew PCBs

Those puppies are faster than grease lightning, they use the structure used 
by pin diodes. I use the 1N4007 to switch rf signals by controlling the bias.

At 05:31 PM 6/20/2005, you wrote:
>maybe this has been discussed but why not use mosfets instead of the
>NPNs?  If you can turn them fully on they will run a lot cooler with
>little voltage drop.
>
>Also, how are you limiting current?
>
>Will the 1N400x be fast enough to supress the spikes?  I thought one
>needed to have schottkys for that.
>
>Reasons to use a PIC (or other micros) is so you can do microstepping
>which makes for a much smoother running stepper and you can use PWM
>(aka chopping) on the coils to allow higher voltage and thus more
>power.  But I'm sure that's all been discussed before.  by the way,
>some of the newer 8 pin Z8s have a tansimpedance amp build in for
>current sense - perfect for a stepper controller.  I'm thinking of
>prototyping with one.
>
>The allegro chips do this pretty well also and allegro is very easy
>when it comes to samples.  I'd look at the A3982, it's new and comes
>in a soic package which is much easier to solder than the older A3977.
>  They'll send 3 units if you ask nice.
>
>Phil
>
>--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan <robert.hedan@v...>
>wrote:
> > TIP31, I've included a parts list on the schematic in the CNC folder
>of the
> > Files Section.
> >
> > Transformer 24V 1.5A
> > 4070 XOR
> > 4027 Flip-flop
> > MCT6 opto-coupler
> > 1K 1/4W resistor
> > TIP31 100V 3A
> > 1N4002 100V 1A
> > Steppers 24V, 36/72ohms, unknown amperage, obsolete model SP57B by
>COPAL.
> >
> > Robert
> > :)
> >
> >
> >
> >
> >
> >
> >
> > What are you using for driver transistors there?
> >
> >
> >
> >
> >
> >
> >
> >
> > Be sure to visit the group home and check for new Links, Files, and
>Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> >
> > If Files or Photos are running short of space, post them here:
> > http://groups.yahoo.com/group/Homebrew_PCBs_Archives/
> > Yahoo! Groups Links
>
>
>
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBs
>
>If Files or Photos are running short of space, post them here:
>http://groups.yahoo.com/group/Homebrew_PCBs_Archives/
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
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Cecil Bayona
KD5NWA
www.qrpradio.com

'Never argue with an idiot. They drag you down to their level then beat you 
with experience.'