Alarm output questions on IPC-HFW4239T-ASE

[SharkyTM]

Hello IPcamTalk folks!

I recently purchased a couple of IPC-HFW4239T-ASE from EmpireTech, and I'm having trouble understanding the "alarm out" wires that are provided. Dahua's spec sheet makes it sound like the output can deliver 300mA at 12VDC (from IPC-HFW4239T-ASE), which I need to use to drive a MOSFET that turns on some security lights.

However, the cameras don't seem to deliver any voltage, and the two cameras behave differently when the alarm output is activated. One goes from open between the Alarm_Out and Alarm_Out_GND wires to 100ohms, as indicated by https://dahuawiki.com/Ip_camera_alarm , and the other goes from open to 0 ohms, which doesn't match anything that I've found from Dahua.

Any clarification on how this output wire is supposed to work would be helpful. I'm trying to drive a MOSFET board that needs between 3.3 and 24VDC to drive the FET, so the 12V promised would be perfect.

@EMPIRETECANDY Any thoughts?

 

[KimmoL]

Quick Start Guide has picture how to connect alarm output. It give "ground" minus to relay. It needs external voltage.

 

[SharkyTM]

Thanks, I'll check that out. I have a source of 12v, so I'll size the resistor appropriately.

 

[tangent]

This type of output is often referred to as a "current sink".

 

[SharkyTM]

Tangent,
Thanks. There's so much information in different places that I must have missed that discussion. It's not an open collector, but a current sink. It'll work, but the behavior is opposite what I need (alarm output on=light off, alarm off=light on). I can spin up a custom little board to make it work, but I was hoping to be able to use a $5 MOSFET board from Amazon that I had kicking around already. I'll just need to swap the polarity of the switch with a BJT.