A burner with a flame detector is provided. An atomizing chamber has an aperture. A flame tube is in front of the atomizing chamber, adapted to direct combusting fuel introduced by the atomizing chamber along an interior of the flame tube. A photodiode circuit is located behind the atomizing chamber. A filter is adapted to filter out signals from the photodiode outside of a predetermined bandwidth. Light from combusting fuel in the flame tube reaches the photodiode through the aperture. The output of the filter indicates the presence or absence of the flame in the flame tube based on at least whether enough light received and converted by the photodiode has a flicker rate within the predetermined bandwidth.