> > PWM high pulse needs to be long enough to allow L1 to draw enough
current
> > but not longer (beware saturation if using this for higher powers.)
>
> What is the effect of inductor saturation on the circuit? How do you
> test for saturation?

Oscilloscope is best bet.
Place a SMALL resistor in series with inductor.
eg if Vcc = 3v and peak current = 20 mA (intended) decide say that 0.1v
across R is ok so R = V/I = 0.1/0.02 = 10 ohm.

Monitor voltage across 10 ohm. Should get a nicely increasing triangle wave
when transistor is on. In saturation this suddenly steepens and trends
towards vertical. At such low currents almost any small inductor will be OK.
As you get slightly higher (say 100 mA plus) quite a few very small coils
MAY saturate.

Without a scope, look at overall efficiency or change of current as voltage
is increased. Scope is by far the best and easiest method.


        RM

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