Apparatus for detecting powder flow along a powder flow path includes a light source and a light detector for detecting light from the light source directed across the powder flow path as powder flows through said powder flow path. A circuit receives the output from the light detector and determines an average or RMS of the signal received by the light detector. The circuit may determine whether there is flow or no flow of powder or whether there is a change in flow rate of powder. Preferably, the apparatus is used in combination with a dense phase powder pump, which causes the powder to flow in pulses from the pump outlet into the powder flow path. More preferably, the light source and detector are enclosed in a housing that is connected between the pump outlet and a powder feed hose which supplies powder to a spray gun or hopper.