With no external power supply except RS232, you may use H11L1
optocoupler and schmitd trigger. Less than 1mA photodiode current. Up to
115 Kbps.
Vasile


Peter Crowcroft wrote:
>
> We are trying to develop a kit where we need to implement an electrically
> isolated serial port between a kit and
> a standard PC serial port.
>
> We have a circuit using opto-couplers (4N25's) but it is not reliable. It
> seems too
> dependant on the IC parameters so that changing the opto-coupler for
> another of the same type affects whether the circuit works or not. Is has
> to do with the turn-on and turn-off delay times of the opto-coupler.
>
> Does anyone have any suggestions or even a (reliable) circuit to do this?
> There is no power supply available on the PC side except what comes out the
> serial connector.
>
> Any advice gratefully accepted.
>
> regards,
>
> Peter Crowcroft
>             DIY Electronics (HK) Ltd
>       PO Box 88458, Sham Shui Po, Hong Kong
> Voice: 852-2720 0255   Fax: 852-2725 0610
> Web:  http://kitsrus.com     Email: peter@kitsrus.com
>     Number One in Electronic Kits Worldwide
> ------------------------------------------------------------------
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads