There are a few things to think about before using a Lightpad. These comments are based on the LightPad Pro 12x12. Power comes from a wall transformer, and the device uses touch-sensitive controls. You cannot turn it on by just supplying power. That rules out automatic control from a timer - probably best to use a red filter or card 'shutter' below the lens. For variable contrast, you need to use below lens filters or put filters above the negative. 12x12 inch above negative sheets are $20 each in the US at the moment, and the below lens filters can be too small for 200mm+ f5.6 enlarging lenses. The unit is also some 15+ inches square and is a bit big for 8x10. There are smaller units but I have not used them.
Since I have one, I tried it as a light source for my nearly complete Beseler MX 8x10 conversion (more about that another time/place). Cranked to full power on a dense 8x10 HP5+ negative it was giving me around 20s f11 at 11x14. Not excessive, but more than usable. You would probably have to settle on a single colour temperature (4600K on the 'High' setting) for calibration.
Really nice light table, and doubles as a room light