btinternet wrote:

any of you have any links a web site where I can get some idea of how to
build a automatic feeder for my koi pond?

Switch to Google and enter "animal feeders" (with quotes) as a search
term. Lots of them around in the US. (Hunters in some parts of the US
are allowed to feed game animals. Sometimes they can hunt over the feed.)

What you are looking for is the basic timing unit, if you really want
to build your own.

I found this complete unit for $50US plus shipping:
http://www.sweeneyfeeders.com/cgi-bin/sf/AF6.html

Looks about the right size for a back yard pond.