Just a couple of comments:

What are you expecting D1 to do? If it is just a normal diode, all it is doing is protecting against reverse voltage. If it is a zener (or transzorb) it will protect against reverse voltage AND overvoltage. What happens if the user wires the board in backwards? Smoke methinks and the board will be damaged. Whilst the diode has done its job, you'll have a repair return and an unhappy customer. A small fuse or a polyswitch here will ensure the board fails without damage (apart from the fuse!). A customer will be much happier if he only has to replace a fuse because of his stupidity. For CE compliance you'll probably need a varistor here also.


With OK1..5 (Opto Koupler?? Sounds a little Germanic!!)
you have weeved a track from your outside world through the cpu side. Not a good idea - try and maintain as much separation as possible - even to the point of using small pads on the optocoupler and don't run tracks between the optocoupler. You're wanting the opto to give you voltage isolation so don't compromise it with your pcb.

Here's a personal comment - screw terminals are fine for small run jobs. They are labour intensive to terminate. From a service position they are a pain as there is always the possibility of getting the wires crossed. You can get screw terminals that plug in which go a long way to solving this problem though they do cost more. Otherwise for high volume production I would normally use a plug in connector with no screw terminals. A lot of my boards go to the worst places on earth and to spend more than a few minutes changing over a suspect board is way too much time. Where possible make it as difficult as possible for the user to stuff things up - there is a limit of course!