Photo Eyes: The Difference Between Reflective and a Twin Beam
Photo eyes send a signal from one side of a gate to the other, ensuring a clear path before allowing the gate to close. A photo beam is a “safety” device because when used correctly it prevents injury to the gate, vehicles, and pedestrians.
When choosing safety devices to meet the UL325 standard, a great option is a reflective photo eye or a thru beam (aka twin beam) photo eye. Considering the following pros and cons when determining which is the best fit for your job.
Reflective Photo Eyes:
Pros:
- Only need power on the operator side of the driveway
- Easy to align
- Easy to adjust
Cons:
- Distances moving through the gate are shorter
- A damaged reflector can cause the photo eye to stop working
- Frost can be an issue when it collects on the photo eye
Twin or Thru Beam:
Pros:
- Distance between the transmitter and receiver is greater than reflective photo eyes
- Works better in inclement weather
- Frost is less of a disturbance compared to the reflective photo eye
Cons:
- Power needs to be on both sides of the driveway
- Takes more time to install
Some Tips for Installing a Photo Eye:
- Check compatibility of voltage and UL requirements of your operator prior to the installation. Specs vary as a result of the manufacturing date and the manufacturer of the operator. Some manufacturers allow for multi voltage — high, low, or both.[1]
- Operators manufactured after 2016 conform to the UL requirements and need at least one “safety” device. After 2018, two safety devices are required.
- Keep in mind, the width of the gate or entrance for most reflective photo eyes ranges between 10 to 40 feet. Anything beyond this requires a twin- or thru- beam style photo eye.
- When installing a photo eye, make sure the transmitter/reflector or transmitter/transmitter is completely level and attached securely to the post or bracket. The most common issue with a photo eye is when one or both sides shift and no longer reach the other side.
- Install the photo eye parallel and within 5” of the gate and at a height of 24” to 30” from the ground to meet ASTM F 2200 code.
- Install reflectors with a shroud or housing to protect them against rain and divert reflection from the sun. Some manufacturers provide a cover for the transmitter.
- When installing photo eyes, be aware of plant, tree, or brush growth. These eventually block the device’s line of sight and lead to service calls. Explain to customers the need to keep surrounding overgrowth trimmed back so the photo eye beam is not blocked.
- Wire the product as recommended by the manufacturer of the photo eye and gate operator.
Ensure Your Photo Eye Works Well.
Since most technical gate calls are usually “photo eye” related, we recommend a couple of preventive measures:
- Explain to your customer the importance of testing the photo eye on a regular basis by intentionally blocking and unblocking the beam.
- Be sure to tell the customer about the importance of keeping the eyes aligned and clear. This will eliminate unnecessary service calls.