On Thu, 22 Oct 1998, Nigel Orr- Underwater Acoustics Group wrote:

> At 10:50 21/10/98 -0400, you wrote:
> >Read the data sheet for the 3700 first.  I use it in my application, but
> >you need a pull-up resistor and capacitor too.
>
> Pull-up resistor on the output?  Can't I just use port B pullups (dragging
> the relevance back to the _PIC_list!)

I've had to use the external resistors and cap for proper operation.
Besides, isn't the pullup on Port B for output only?

> One other question- the threshold voltage in the 3700 is 6V- I know from

The threshold voltage for turn-on is 4.23V when used with a AC input.  Of
course you need to put a limiting resistor on the input side to reduce the
current to a level where ytou don't burn the device out.

Read the last page of the data sheet!  It shows a sample circuit,
equations for the resistor values and so on.  Remember to figure the
power dissipation in the rsistor and choose accordingly.  If you don't
understand it, please e-mail me.

Rob


>
> Nigel
> --
> Nigel Orr                  Research Associate   O   ______
>         Underwater Acoustics Group,              o / o    \_/(
> Dept of Electrical and Electronic Engineering     (_   <   _ (
>      University of Newcastle Upon Tyne             \______/ \(
>