Re: [CAD_CAM_EDM_DRO] Re: Stepper Motor Driver

irf needs more than logic high to turn fully on.
and you DO want the fet fully on- otherwise it's a
resistor and will dissipate heat (W = i^2R, where R is
the rds on), so then you're adding heat sinks for
sure.
so you want them fully on- then they're virtually a
switch.
the fets you have are not logic fets and you should
get the data sheet to see what the vgs is needed to
get minimum rds on - that is, what gate voltage turns
the fet fully on so it has the lowest resistance.
i totally recommend irlz54 -
BUT-
if you use the optoisolated circuit, you get to use
any voltage required on the gate of the fet, though
you'd have to supply it somehow.
again arguing for the irlz logic rets.

a 5v motor can use a 5v power supply and you won't
need any resistors in series - they just heat the
room.
furthermore, you isolate your computer from any motor
noises.
microstepping makes a motor run smoother. that's the
latest rage. this gives improved performance under
certain conditions, but won't change the quality of
the part that comes off the table.
half stepping IS valid resolution...beyond that,
microstepping is spurious on that respect.


--- Blue <jo001k1132@...> wrote:

> Hi Dave,
>
> With every new suggestion the price is going up and
> I wanted to do this
> particular machine for next to nothing, it being
> just a first machine and
> really a play-thing. The original board I posted for
> information on is under
> £10 ($15) each (that is £12 with postage)and I could
> have just thought of
> using the design, as I have about 200+ FET's IRF630,
> these are very high
> voltage (600) and 9amp. I believe they also have
> diodes built into them. I
> also have a large box of logic chips. I'm very good
> at assembling electronic
> circuits but cr*p at the theory. Even ohms law has
> never sunk in.
>
> Regards,
>
> Terry
>
> | > Hi,
> | >
> | > I thank you for the offer but I'm sure I can
> build it with
> | strip-board. I
> | > take it this company has upset you?
> | >
> | > Regards,
> | >
> | > Terry
> |
> | The Kits-r-us curcuit is the same thing, (except
> for the optos) and is
> | available for many sources.
> |
> | I do like the robotstore circuit better, but don't
> see much difference.
> |
> | Since you are not is the states, your list of
> vendors is not as large
> | as ours.
> |
> | The kits-r-us board is available from many
> suppliers, this being the
> | lowest cost in the states.
> |
> | http://store.qkits.com/moreinfo.cfm/QK179
> |
> | But, at $40 per board, I would opt for the
> HobbyCNC board for being
> | microstepping, lower in cost and with chopper
> circuitrs and not
> | needing resistors.
> |
> | Dave
>
>
>
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