Selecting a Photocell
Many low voltage situations involve very little power, so that the
photocell can be small in size, where voltages and/or currents are
higher, the photocell must be physically larger so that the
semiconductor film can dissipate the heat.
Maximum Cell Voltage
At no time should the peak voltage of the cell exceed its maximum
voltage. the designer should determine the maximum operating or
peak voltage that the cell will experience in the circuit and choose an
appropriately rated cell. Typical voltage rates range from 100V to 300V.
The following curve of power dissipation versus ambient temperature
describes the entire series of cells for operation in free air at room
ambient (25°C). Note that regardless the size, all photocells derate
linearly to zero at an ambient temperature of 75°C. The adequate heat
sinks can increase the dissipation by as much as four times the levels
shown in this graph.
What Type of Material is Best?
Each specific material type represents a trade off between several
characteristics. Selecting the best material is a process of determining
which characteristics are most important tin the application.
PerkinElmer’s standard photocells in this catalog are manufactured
using one of two different material types offered: type “Ø” or type “3”.
In general, material type “Ø” is used for applications such as
nightlights, automotive sensors. Material type “3” is primarily used in
camera, streetlight control, and flame detector applications.
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