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0-10V Photocell Troubleshooting

Last modified by Alexander Mott on 2026/05/07 22:32

Analog photocells measure light at the photocell and output a 0-10 V DC signal. On GLS-LDL photocells, this signal is output over the orange wire, with the red wire corresponding to 24 V DC input and the black wire corresponding to ground. 

Reading is Stuck at 0% or 100%

If an analog photocell (i.e. a 3-wire 0-10V photocell, not a Cresnet or internal occupancy sensor photocell) is correctly defined in the ShowRunnerCLC™ configuration but you see a 0% reading when looking at the photocell in XPanel or running the sr show photocell command, perform the following troubleshooting steps:

  1. Verify the ShowRunnerCLC™ configuration:
    1. Id should be a number without quotes matching the dictionary ID (the quoted number at the top of the photocell definition)
    2. Model can be "GLS-LDL", "GLS-LOL", "GLS-LCL", or "GLS-LEXT" for non-system sensors
    3. HostDevice should be the model name in quotes for the device the photocell is wired to (GLS-SIM, ZUMLINK-JBOX-16A-LV, ZUMNET-JBOX-16A-LV, etc.)
    4. HostPort will be 1 for most devices. Exceptions are:
      1. GLS-SIM or C2N-CBD-P where the photocell is connected to port 2 will be 2
      2. GLPAC will correspond to the number of the dedicated photocell port that the photocell is connected to (1-4)
    5. DeviceHostId is the IP-ID in quotes for the host device or null without quotes if connected to a device without an IP-ID (e.g. a GLS-SIM connected directly to the processor)
    6. DevicehostBranch is 1 for most devices, with the exception being devices on DIN-CENCN-2 net 2 where the DeviceHostBranch will be 2 and devices directly on a processor where it will be 0
    7. DeviceConnectionId will be the hexadecimal CID (Cresnet ID) of the host device in quotes
  2. Verify the photocell is connected to the correct device (compare serial numbers to ensure the IP-ID, CID, and model match of the host device matches the configuration)
  3. Verify wiring at the host device:
    1. For ZUMNET/ZUMLINK-JBOX the photocell should be using ports 4, 5, and 6 on the green terminal block, corresponding to 24V (red at the photocell), signal (orange at the photocell), and ground (black at the photocell)
    2. For GLS-SIM, there are two ports with two dipswitches each:
      1. Dip switches 1 and 2 correspond to port 1 while switches 3 and 4 correspond to port 2
      2. Dip switches are all in the on (up) position from factory, but photocells should have the dip switches for their port set to on-off (up-down)
  4. Verify signal/power at the host device:
    1. Verify the host device is outputting 24V on the correct port
    2. Verify you are receiving a 0-10V signal at the host device by disconnecting the signal wire and measuring its voltage to ground
      1. You should see a sensor reading between 10V and 0V, with 0V being the reading when it is covered up. Ideally a second person will be at the photocell to shine a light or cover it up to verify readings are changing
    3. If there is no 24V output, then the host device is probably faulty and you should contact Crestron for troubleshooting or replacement
    4. If there is no 0-10V signal, proceed to troubleshooting at the sensor
    5. If there is a reading above 24V then the cabling is incorrect (either the signal is shorted to 24V or the cable actually goes to something other than a photocell, e.g. a non-system occupancy sensor)
  5. Verify signal/power at the sensor:
    1. Verify 24V is reaching the photocell by disconnecting the photocell's red wire and measuring voltage on the cable from the host device
    2. Verify the photocell is outputting a 0-10V signal by disconnecting the orange wire and measuring voltage on the orange wire
    3. If you get a reading at the photocell but not at the host device then there is likely a wiring issue, such as the wrong cable or wire is connected or the cable is damaged in the field
  6. Check the jumpers/switch at the photocell to make sure the reading is in the correct range:
    1. Open loop 3-300fc (default)
    2. Open loop 30-3000fc (bright windows)
    3. Open loop 60-6000fc (skylight/exterior application)
    4. Closed loop 3-300fc (downward facing photocell)

Reading Reports Inverted

Inverted readings in ShowRunnerCLC™ are usually the result of incorrect dip switches at the host device such as a GLS-SIM. This can be corrected without physical access to the host device by changing the Invert property in the config from false to true

Reading Reports Higher or Lower than Expected

If a sensor is reading very high, very low, or is not reacting much to changes in light, the most common causes are:

  1. The photocell is installed incorrectly (i.e. the location is too far from a light source, the view of the light source is obscured, or the photocell is installed facing away from the light source)
  2. The jumpers or switch on the photocell (depending on whether the photocell is rated for wet locations or not) are set to the incorrect range for the installation location. The available options are:
    1. Open loop 3-300fc (default)
    2. Open loop 30-3000fc (bright windows)
    3. Open loop 60-6000fc (skylight/exterior application)
    4. Closed loop 3-300fc (downward facing photocell)