This video walks through setting the Timelapse+ and camera for a day-to-night auto bulb ramp using the latest firmware with the new ramping algorithm. The new algorithm incorporates many improvements and produces smoother results with a target dark point, so you can be confident the night exposure will be exactly as desired. The light sensor is only used to guide the transition from the manually exposed starting point to the selected ending point. This gives more control and more repeatable results.
If it's too painful to listen to me talk for an entire 16 minutes, you can download the PDF overview here: timelapseplus.com/manual/TLP_Day2Night.pdf (this is my preference!)
Requires firmware version 20131202 or newer: firmware.timelapseplus.com