One of the main problems with magnetic ballasts is that while they can con-
trol the current to the light, they cannot alter the frequency of the input power.
Because of this the lamp illuminates on each half-cycle of the input power
causing the lamp to flicker and produce a low humming noise. This flicker
can cause eye strain and headaches in some people and the humming can be
bothersome and distracting. Electronic ballasts control input frequency, thus
eliminating these problems. Another advantage of electronic ballasts over
magnetic is that one electronic ballast can control more than one lamp, allow-
ing for multilamp fixtures to be controlled by a single ballast.
Fluorescent ballasts come in three different types: rapid start, programmed
start, and instant start. Rapid-start ballasts start lamps by simultaneously pro-
viding voltage to the electrodes and across the lamp itself. As the electrodes
become hotter and emit more electrons, less voltage is required for the lamp and
eventually the cathodes will become hot enough to ignite the lamp on their own.
Programmed-start ballasts are more advanced versions of rapid-start ballasts.
They have preprogrammed start-up sequences designed to give superior longev-
ity to lamps. Rather than supplying simultaneous voltage, programmed-start
ballasts first apply voltage to the electrodes to heat them up for a short interval,
then apply voltage to the lamps. This helps avoid a common problem in fluores-
cent lights called “tube blackening” which occurs when the electrodes are dam-
aged from voltages without sufficient heating. Programmed-start ballasts have
the longest lamp lives and are best used in locations with lights that are
constantly being turned on and off.
Instant-start ballasts start lamps by providing high voltage directly to the
lamps without preheating the electrodes at all. Because there is no heating
time, light is produced within 50 milliseconds, thus giving it the name “instant
start.” Instant-start ballasts have the highest energy efficiency of any ballast
and the lowest cost however they suffer from emissive material defects like
the rapid-start ballasts. Instant-start ballasts are best used in lights that are
not turned on and off very often.
For certain applications where a light is intended to be constantly turned on
and off, such as a flashing light, there are ballasts that will keep the electrodes
heated even when the light is off, thus greatly increases lamp life span.
Integration into Building Automation Systems
Lighting systems provide a life safety function, assisting in security or lighting
evacuation pathways from a building. Lighting systems may be integrated with
fire alarm systems, security systems or emergency power generators. In the
56 Smart Building Systems for Architects, Owners, and Builders