Thanks for the info!! =20

That's cool....10ma should keep me from frying my new 628.  Last one =
sourced a bit to much :)  I can live with 3.4 uS....oh...2 million uS =
just=20
went by as typed this....swosh.....

That brings up another Question.

I just bought an O'Socpe and some places on the web show it to be 100 =
MHZ....and others show it to be 20 MHZ.  I did some math and I agree with =
20 MHZ.  It's a Tek 465 and the dial goes to .05 uS.  If .1 us is 10 =
MHZ....then .05 should be 20 MHZ..  Am I missing something here?

Thanks,
Tim

>>> mapr@COMCAST.NET 12/23/03 10:29AM >>>
If the FET you are using is a logic level like IRLR3410, you can use a 500
Ohm resistor which would limit your output pin current to about 10mA. =
Given
a gate charge of 34nC for the FET, the switching time for the FET would be
about 3.4uS (gate_charge/current_into_gate=3Dswitching time). If this is =
too
slow for the application, you can reduce the gate resistor further; the
constraints you have are the peak current your output pin can source (say =
20
to 25mA for a PIC16F876). Also keep in mind that the faster you switch you
FET, the more the chances for a di/dt induced false turn on and other =
nasty
effects.
Madhu

>-----Original Message-----
>From: pic microcontroller discussion list
>
>I'm building something similar and was wondering what resistor to
>use for my gate on the MOSFET?
>
>Thanks,
>Tim
>
>>>> mapr@COMCAST.NET 12/22/03 04:17PM >>>
>Most, but not all, Solid State Relays (SSRs) are optoisolated; essentially=

>an opto-isolator with a FET or a transistor output stage. You can get =
both
>AC and DC flavors of SSRs. Digikey has a bunch of pages of these. If an =
SSR
>is rated logic level then you can drive them directly from a PIC pin with =
a
>current limiting resistor. For the Solenoid valve you can just get a N
>channel logic level FEt and with a suitable gate resistor drive your
>solenoid to ground. For the high amp element you might consider a AC =
solid
>state relay that can be mounted to a panel.
>Madhu
>

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