If you want to download any files, such as schematics, consider a small fee, 100 SEK perhaps but choose the amount after your own abilities. Customers will of course download for free.
A donating diyaudio.com member (the star under your name in the posts), will also download for free. In that case state your username so I'll can check this.
If you use the paypal button, please notice that SEK is the currency which I want you to use. Notice also that Paypal accepts credit cards also without any need for having an Paypal account.