Vasile Surducan wrote:

> > Vasile, 24v at only 300mA is well within the
> > range of the cheap circuit with a pre-wound
> > inductor costing a few cents. Two transistors,
> > cheap inductor, no need for a chip or otherwise.
> > I've spent years winding ferrites too and its
> > nice sometimes not to have to do it. :o)
> >
> > If REAL efficiency is needed I would PWM the
> > solenoids direct like Alexandre suggested, as
> > you can give them full current for just long
> > enough to "pull-in" and about 1/3 the current
> > for holding.

>   Roman, 70V to 24V and 24V to 5V using two
> separate supplys, sound for me a little strange
> even at 300mA.
> One transformer with two output coils, one for
> +24V ( and/or driver) and another for +5V sounds
> better. At this current, efficiency of up to
> 85%...90% can be easily obtained.
> The solenoid ( or transformer as I suggested,
> to isolate the output ) is not a big deal, small
> core, tiny wires. A HV driver can drive directly
> the transformer. Resonant solution may minimise
> the input current and increase the efficiency.

Sure. But winding a dual output former is
scary for some people and always takes time
to wind it and tune it. Then which rail do you
regulate? The 5v is only 30mA and regulating that
one will allow the 24v 300mA to be very sloppy.
Or regulate the 24v rail and use a 7805 etc
for the 5v rail? That's 2 chips and a special
transformer now. :o)

I just got a smile from the thought the
2-transistor circuit we all worked on might get
used for a "real" project ha ha! :o)

> Just a thought, don't kill me [grin]
> I'm glad you're OK.

Thanks for the concern! :o)
I don't kill people, well maybe if you get on
the back of my bike ha ha!! Seriously I ride
VERY safe with a passenger.

Did you like my RC solenoid driver circuit?
-Roman

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