Thanks for the advice boys.
I will have a look at Vems. I concidering using an EDIS-4 with toothwheel. I will have a look at the yunkjards soon.
The potentiometer will be from a old audiomixer, placed in a waterproof housing. I will place a picture as it's finished. Low budget and homemade brew.
It will look awfull, but I don't care.
CU, Frank.