Use of the StarDot Trigger Input in POE Cameras and Domes

The NetCamSC and NetCamSCD products use an opto-isolated input trigger, which is appropriate for POE devices.  This type of trigger input requires a small voltage to be applied across the trigger inputs in order to activate the trigger.   This is different from StarDot products which do not contain POE.  In those designs, an internal resistor puts a ‘1’ signal on the trigger, and you can short circuit the trigger input to a ground on the same connector, to generate a ‘0’ signal. This was convenient for magnetic door switches.

The same is true in the SC products, except that short circuiting the inputs will not work. You must provide a voltage between 3.5 and 5.9V. An alarm signal can provide this voltage, or you can wire another voltage source for use with the door switch. For testing purposes it’s ok to use a 9V battery as is shown in the following picture, as long as you do not reverse the + and " wires.

From telnet, enter this command (this assumes the triggers have not been altered with another command, which is the boot up condition):

Mbus /dev/io w 2 r 1

With no voltage on the trigger, you will get: 01

With a voltage applied, as shown in the picture below, you will get: 00

Note: make sure you push in the connector’s orange part with a fine screwdriver, push the wire far enough inside to make bare wire to metal contact, then release the screwdriver and give a light tug on the wire, to prove it has a good connection.

You can also access this information from the API as follows:

When the trigger voltage is present, use a browser to go to this web page inside the camera (substitute your own IP address):

You should see:



For the technically minded, POE products require a fully independent voltage, instead of a more convenient internal signal to short to ground, because a ground loop can be created back to the POE device if the camera has any power connection in common with the outside wall supply (from which the POE powering switchbox gets its power).   The external voltage can be generated from the wall supply or a battery, but it can’t make actual electrical contact inside the camera.  You can use external voltages higher than 6V.  Up to 12V can be used normally, as long as polarity is observed (connecting the + and " correctly).  Damage should not occur until +-20V is exceeded. However for proper operation you should add a resistor when you intend to use a higher voltage, as follows (the amount of current required is approximately 3mA):

6V to 10 V = 1K
10V to 16V = 2.7K
16V to 26V = 5.1K
26V to 38V = 8.2K
38V to 65V = 15K
65V to 93V = 22K
93V to 136V = 33K

Article ID: 190
Last updated: 11 Jun, 2020
Revision: 1
PRODUCT SUPPORT -> IP Cameras & Video Servers -> NetCam SC -> FAQ -> Use of the StarDot Trigger Input in POE Cameras and Domes