From: "Dwayne Reid"

 Ray Gallant wrote:
> >My solenoid load is (24VDC, 800mA). The PWM is 20kHz, (pic driven).  The
> >opto-coupler output is 5 volts.  The FET's high level input is 5
> >volts.  Will this opto drive the FET properly? (y/n) Cost is not an
issue,
> >but performance is.  I will address filtering later!
>
> I've read some of your later responses and can offer my experience.
>
> It sounds as if you are driving a hydraulic control valve.  I do this in
> several products using a low frequency PWM current source based on a
SG3526  PWM controller.  I mention that my feedback is current rather than
voltage this reduces the inaccuracy caused by temperature changes in the
solenoid  winding.  My PWM frequency is around 500 Hz - this low frequency
causes vibration which reduces the hysteresis caused by the solenoid core
> 'sticking' in place.
>
> Now back to your FET driver.  You say that the opto-coupler output is
> 5V.  Where is the 5V supply coming from?
>_________________
Things are going slow today: had to replace the thermal circuit breaker in
my coffee machine! grrrr.
All on the high side of the opto:  I have a 24VDC.  I plan, later, to add
filter stages with plenty of bandwidth utilizing operation voltage of 5VDC.
For the moment, I have used a LM317L regulator to provide 5VDC.

Tx for the feedback, I will definitely check out this concept/avenue.
{slewrate}

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