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Tech Tip 16

Compact Fluorescent Interference


SYMPTOMS

  • TV, VCR or other remote controls quit or do not work correctly, i.e. channel switching
  • Loss of control from infrared detectors such as automatic doors or position sensors
  • Compact fluorescent bulb or high efficiency fluorescent lighting located in the room

CAUSE

  • Fluorescent lamp emits high frequency infrared light on infrared remote receiver

SOLUTIONS

  • Relocate lamps to reduce their light from hitting the receiver
  • Replace lamps and/or ballasts with different brand or model

BACKGROUND

Compact fluorescent light, CFL bulbs and some fluorescent ballasts increase lighting efficiency by driving the lamp at frequencies higher than the 60Hz utility power. They produce light that looks constant to the human eye. Careful examination of the light with instruments shows some ripple at twice their switching frequency.

Some of the light from all lamps is infrared and not visible to humans. The infrared light from these lamps also has ripple characteristics at twice the switching frequency.

Most remote controls for TVs, VCRs, and CATV controllers use infrared light to communicate. The remote control receiver must be able to detect very low light levels from the hand-held remote control. This sets the stage for problems.

The infrared light ripple from the lamps sometimes is close to the carrier frequency of the remote control. Problems occur when the high frequency infrared light overpowers or confuses the receiver as in Fig 1.

 

Figure 1: Fluorescent Light Interference with Remote Controls

This causes loss of control, volume drift, channel changing, and related problems for TVs VCRs. Similar problems occur for other consumer remote control products.

Commercial and industrial buildings can experience similar problems. TV stores are especially susceptible. Sometimes motion detectors for automatic doors are affected. Infrared position sensors may also be affected.

SOLUTIONS

Unfortunately, it is difficult to predict problems without detailed technical information. There is little coordination between lighting and remote control manufacturers to prevent problems. Some lights are more likely to interfere than others. Some remote controls are more sensitive than others.

For residential problems with TVs, the offending bulb may have to be moved so it's light does not land on the TV. A different lamp shade might help. Another solution is to try a different lamp brand or model. These may prevent unnecessary service calls from TV repair shops.

Commercial and industrial applications should consider possible impacts in advance. Most lighting catalogues will show the switching frequency of the high frequency ballasts. The infrared light frequency will be twice the switching frequency. Check with controller specifications to avoid problems.

The information and diagrams presented herein are for general educational purposes only, and should not be relied upon as instructions for customer self-wiring. Customers should at all times seek the assistance of qualified electricians or utility personnel for all wiring projects.