Re: emitter followers / Darlington - need help


Jonathan Kirwan wrote:

....


Why the 47k R1 though?

It pulls the gate of the IRF530 up when the TIP31A is off. Otherwise,
you'd have a similar problem as before. The value of 4.7k is a guess.
You could try the 2k, as well. Should be about the same behavior, I
was just trying to lighten the load on the parallel port a little bit.
R1 will need to be smaller values for faster operation, I suppose. I
didn't look at the IRF530 capacitance; and for now, I don't care to
find out. But it will limit the turn-on rate of the IRF530, which
could be a small problem. Would need to know a lot more about what
you are wanting to try, though. And by then, there would probably be
a much better topology to use. So why bother, for now? Mostly, I'm
just wondering how that seems to work using the parts you have on
hand.

Jon



Gotcha. Thanks.

Basically just trying to learn. I'm using a lamp for now... once it
works properly, I'll use my motor, with capacitors to smooth out the
power.

I already built a 555-based PWM thingie off a schematic off google;
that works great. I just thought with a parallel port's 8 pins, I
could potentially control 8 motors simultaneously, from a DOS program
on my laptop. It's a learning exercise (and I have so much to learn!)

Michael

.

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