So I don't know if it's been done before (probably has) but I managed to make an auto turntable. This is my first try (and I haven't watched any tutorial videos) so be nice please. :)
The cool thing about this is it works with no lapis required which is good for me cause I'm playing Better Ore Distribution and have yet to find a vein. Anyway without further ado here it is.
Note that the timing turntable is on it's longest setting to make soul urns. One before the longest seems to usually make planters. The disadvantage of this setup is precision. Sometimes it goes too long and turns the urn into a clay ball. But that's not so bad cause you just go to the hopper underneath and grab all the clay to reload.
I've used a similar build. I prefer timing off a turntable and a Block Dispenser/cotton array to using a BUDdy block. What I've found is that there's always a little wiggle to the timing: It seems like you either undershoot and sometimes get a vase, or overshoot and sometimes get nothing but clay balls.
My turntable/wool+blockdispenser pottery occasionally produces vases as well. I've figured out by now that it seems to happen when I leave the world and return. It just screws up the timing. Fortunately the stuff it makes isn't fed into a kiln automatically, so I can just destroy the vase and recreate two urns.