Re: [CAD_CAM_EDM_DRO] Re: Parallel port relays - kit

Hi Dave,

It's not really a software problem, unless you mean giving serial port
choices for pin drivers.

If you really had to have a "dongle" for a serial port, there are at
least two output lines, CTS & DTR, that can be used to drive external
devices. Trouble is, they are (or should be) +- 12V signals (RS232).

A level converter is a chip used to go to/from TTL logic and RS232.
MAX-232 comes to mind.

http://www.lookrs232.com/rs232/level_converters.htm

However, a series limiting resistor and a clamping diode into a driver
IC or transistor should work as well. Lots of low cost PIC circuits
(and uP) use this for a cheap serial data input.

On the software side, it's as easy as a port write or two at the serial
ports control address.

Alan KM6VV

>
> This is where my WISH LIST for software developers comes in.
>
> I would like to have a serial port connection run the relays. many
> relays are for things that do not have any timing issues, coolant
> pump, vacuume, clamps... etc... Having use of relays on the serial
> output would offer some neat possibilities.
>
> Maybe for that EMC port......
>
> There is 12 volts inside the PC, so that is not an issue.
>
> Dave
>