>Hello,
>
>    I'm working on a device that uses a solenoid to spurt a little bit of
>liquid from a recipient with a nose (jet). This is working very well, but I
>would like to implement a way to the PIC to know if the tip is obstruct.
>
>    The solenoid is 24V and is fired for about 25ms with a darlington par
>with a BC548C and a TIP41C. I think that when the tip is obstructed, the
>inrush current to the solenoid is a bit higher than otherwise. If so, I can
>make something like an integrator to measure the total power (uW/h=3F) that
>was sent to the solenoid and know if the tip is blocked or even partially
>blocked.
>
>    Someone have used something similar=3F Would it work=3F Actually I

>have instrumentation to measure solenoid current to know if I'm right.
>
>    Thanks,
>
>    Brusque
>
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>Edson Brusque                 C.I.Tronics Lighting Designers Ltda
>Researcher and Developer               Blumenau  -  SC  -  Brazil
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>
> The current in the solenoid is exactly the same whether it
> moves or not,
> but its slope is not, because L changes with the armature moving. I
> suppose low L for unmoving and higher L *after* moving. If
> you look at the
> energy of the decay pulse (when you release the Darlington),
> the high L
> should give you higher energy. If the solenoid closes the
> magnetic circuit
> fully when it strokes to the end, the increase will be large,
> otherwise
> pretty small. You could measure this with a current sensor in
> the kickback
> circuit driving a simple integrator.
>