Dan Tye wrote:
>
> Hello PICsters!  I was wondering if anyone has experience with parallel port
> isolation.  Here's the deal, I have a design where I have many 17C756 based
> peers on an RS485 network.  I am distributing power (24V DC) to every device
> on the network and every device contains regulators to derive their specific
> needs from the supplied 24V and ground.  Great, now I don't have to worry
> about differing grounds, right?  Wrong, unfortunately I cannot completely
> isolate this system from external grounds because I need to communicate
> through a peer to a printer and a PC.  Question is, how can I isolate the
> printer interface from the rest of my bus?  I am thinking now to comm via
> i2c to a 17c756 that will then output the data on one of its I/O ports as
> parallel data, but I will have to isolate somehow, maybe through
> optocouplers, but I don't know much about them.
>
> Any ideas?
>
> +++++++++++++++++++++++++++++++++++++++
> ++      Dan Tye
> ++      Chief Engineer
> ++      Tel-Tron Technologies Corporation
> ++      220 Fentress Boulevard
> ++      Daytona Beach, FL 32114
> ++      Phone: 904-255-1921    Fax: 904-258-3782
> +++++++++++++++++++++++++++++++++++++++
 Use a a 4N35 Optocoupler (pinout is in DigiKey catalogue)  use it to
switch the ground, that also enables you to switch higher currents
(relay etc.)  logic level in , high = good ground. Use a 670 ohm
resistor on the input, as if it were an LED

Daniel Jircik
pannomat @swbell.net


SUBSCRIBE PICLIST