Embedded systems wrote:

> Brent, it's not the initial moment (t=3D0). But immediately after the tur=
ning
> on.
> Take a look please at his pictures showing the voltage across
> the current sensing resistor:
> http://orlandorobotbuilders.com/stuff/BIM2-01.jpg

Thanks for clarifying, I see now.
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> So, on 50miliohm and about 280mV seems to be about 5.6A after turn on and
> slow down to
> 1A in normal run.

I believe the 1A is the "hold" current he is acheiving using PWM to reduce =
power.=20
The initial "full power" period makes sure the solenoid/injector repsonds a=
s quickly=20
as possible.

> If he measured the voltage drop across drain-source in the same time, he
> may knew if that
> current is producing the transistor dissipation or not.
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>=20
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> On Thu, Nov 26, 2015 at 11:04 PM, Brent Brown <brent.brown@clear.net.nz>
> wrote:
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> > On 26 Nov 2015 at 20:31, embedded systems wrote:
> >
> > > Schematic looks good.
> > > I prefer a fast rectifying diode in anti-parallel on the load versus =
your
> > > zener on the MOSFET.
> > > Maybe you should try.
> > > At turn on you have 4x nominal current on the load.
> > > Say the value of this current.
> >
> > How at turn on can you have 4x nominal current? Inductor theory tells m=
e
> > at t =3D 0
> > current =3D 0.
> >
> > http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html
> >
> > Not being critical, I'm just curious where your idea (rule of thumb?)
> > comes from. It's
> > not uncommon to hear people associating "inrush current" with inductanc=
e.
> > In AC
> > circuits it's a different ball game, assymetric currents due to phase
> > angle at switch
> > on etc.
> >
> > Brent
> >
> >
> > --
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> >
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