I'm having the same issue, using ramps 1.4 to drive servo, but it's not working, before plugging it to the ramps 1.4 I tested it with my arduino uno and it works, currently I didn't test it after plugging it to ramps 1.4.
I think there's a bit of problem in marlin or something,
I can only answer your second question, I tried using inductive sensor, If you already have aluminum bed, you can just use the inductive sensor, I tried to use the inductive before and the sensor somewhat brushing with the printed parts. Aluminum being with less conductive with other stuffs but won't rust, the detection range have been reduced to 2mm, which is quite short for my own opinion.
For me, I would go for capacitive sensor, acts the same way as inductive and the range are much longer and able to detect other surfaces as well at the cost of fatter barrel
Update accordance to controlling the servo in ramps 1.4:
Actually there's another 2 pin you need to connect to the left of the reset button, connect both pin labeled 5v and vcc via jumper or anything that's suitable to supply power to the servo pins there. I got mine working fine and there's no jerking after initial movement (not tested on pronterface yet but it moves a bit when printer powered up). I'll go for servo compared to inductive although bit more complex but on a bed that is tilted a lot, it is suitable compared to inductive at 2mm range especially on my groove mount, it is about 50mm to the left of the head, quite far from it
Edited 1 time(s). Last edit at 09/17/2015 07:53PM by sarf2k4.