Removing the IR lights in a Foscam FI9805W

A year or so ago we bought a CCTV camera for the house, as we seem to have oiks throwing stones at our patio doors every year or so, and we wanted to at least know what they looked like.  We got a Foscam FI9805W which is a high definition, weather resistant, motion detecting WiFi camera that allows us to connect to it from anywhere – and fairly cheap and cheerful, but seemed to have what we needed.  In general, we’ve been happy with it, but it has one really annoying deficiency.  At night, it turns on a bunch Infra Red LEDs, and ta-da, night vision.  The trouble is, that the various bugs and spiders quite like the warm light, and fly/crawl up, and the motion sensing triggers.  Roughly every minute or two, all through the night.

My first thought was to use an external IR light, and one quick ebay later we had one.  But, it turns out if you turn off the IR illuminators on the camera, it turns out it also leaves the IR filter in place in front of the lens, so you see nothing.

A quick web search shows that similar issues with other Foscam cameras.  The IR cut filter is triggered by the IR illumination tuning on, so if you turn it off, the cut filter stays in place.  I can see how it happened – first came the illuminators, then the IR cut filter was added.  But, it’s really annoying.  The web also has some guides on how to bypass the LEDs, but not for this model of camera.  So, for future searchers (yes, this WILL do damage to any warranty!) …

First, remove the sun cover and unscrew the front glass lens cover :-

Then, remove the four screws holding the illuminator and camera boards into the camera

Now the illuminator board can be detached – there are four screws, and two cables (one with yellow wires, the other with red) to be removed – watch the cables; the plugs are hard to remove and I suspect that it would be easy to break them.  I had a temporary hope that one of them would be the LEDs, and the other the sensor, and one could just be left unplugged.  No joy.  They both appear to have power and ground, with the yellow one also having an activation line.

The aim here is to take the LEDs out of circuit, but leave the sensing working.  The LEDs appear to be in 6 parallel sets of 6 series connected diodes with a dropper resistor across the end of each. Tracing the circuit is a pain as its a multi-layer PCB.  The dropper resistors are easy to find as they are just the 6 biggest ones.  In the picture below, they are labelled R3 and R7 on the left hand side half way up, and R17, R18, R5, R2 on the right hand side running from half way down downwards.  They all need to be taken off – not too tricky with fine nose pliers and some care with a fine soldering iron.  Keep them if you ever might want to reverse the process.

I did hope this would e enough, but it wasn’t quite.   The trigger is now floating unconnected unless activated, and needed to be tied to the power line.  So, I added a 220k ohm resistor from between the +Ve rail and the old resistor feed.  there is no easy way to find the +Ve line, so I traced through a set of the LEDs until I found the end of a chain of 6, that was a sensible distance from one of the resistor feeds.  If you find the same board as me, you can see this below.  Note that the upper lead of the resistor is soldered to the lower of the pads for the resistor, even though the photo makes it look like it is the upper one.

In customary fashion, reassembly is the reverse of the above.  And … it works exactly as desired.  The IR control now affects only the IR cut filter. 

If you wanted to be able to switch this all back to the way it started, you could put a waterproof switch on the back of the case, switching a replacement dropper resistor in and out – the pull-up resistor could be just left.  But, I can’t think why I would want more video of flying insects & spiders!