Here's my current rig. It's a P.I.D. temp controller with a 25mm ID coil sourced from an injection molding setup. It uses a k-type thermocouple for the sensor, and thus is 5 rail grounded AC current. The controller is rated at 250w, but my coil is only 150w. Ramp time is a few minutes, but I leave it on all day, so no worries there. The vaping surface is SiC, or silicon carbide.