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PECUs typically use one of three devices to switch the load:
Thermal relay
Suited to use with CdS sensors, thermal relays have a number of drawbacks, principally power consumption and size and are increasingly being replaced by products, which use other load-switches. They operate by the action of a heating element on a bi-metal strip, as the strip deflects it causes contacts to make, or break.
Electromagnetic relays
Electromagnetic relays are small, capable of operation at low power and widely used in many applications. They are relatively poor at transferring high inrush loads (common to many street lighting applications) however this can be mitigated by techniques such as predictive load transfer.
Semiconductor
There are a number of semiconductor devices capable of switching street lighting loads. Triacs are most common; however Thyristors and MOSFETs have also been used. These devices are reliable, simple to control and are effective at transferring high inrush loads. It is relatively easy to implement zero-cross switching with semiconductor switches
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Consumption |
Load Switching Capacity |
Load Holding Capacity |
Size |
Thermal Relay |
Poor |
Moderate |
Excellent |
Large |
Electromagnetic Relay |
Moderate |
Moderate |
Excellent |
Moderate |
Semiconductor |
Excellent |
High |
High |
Small |
Also see
To find out more about the Zodion Lighting Controls range of Photo Electric Control Units, please browse our catalogue pages.
Our PECUs range includes:
If you have any questions, please contact us on 01422 317 317 or fill in our contact form we will be delighted to answer any questions you might have on PECUs.
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