An electrophoresis controller for use with an electrophoresis apparatus having a gel matrix disposed between electrodes for separation of particles along with a tracking dye. The electrophoresis controller includes a sensor system and a controller. The sensor system includes a support, a light emitter, and a light receiver. The support includes a first portion positionable on a first side of the gel matrix and a second portion positionable adjacent a second side of the gel matrix. The light emitter is positioned on the first portion of the support for emitting light onto one side of the gel matrix. The light receiver is positioned on the second portion of the support adjacent to the other side of the gel matrix for receiving light from the light source as it is passing through the gel matrix. At least one of the light emitter and the light receiver includes a light guide having a first end and a second end. The first end is positioned on the support and facing the gel matrix, and the second end is remote from the sensor system. The controller is operably connected to the sensor for monitoring a change in the light from the illuminated gel matrix due to migration of the tracking dye into the illuminated gel matrix and received by the light receiver.