Friday, September 6, 2013

OpenWRT based Video Recording System - Part 1 - Hardware

An OpenWRT router can be used to capture video with a usb webcam in order to record movements in a room. The internal flash storage for the MR3020 is only 4 Mb which isn't sufficient for storing video. So additional storage is required, which can be provided by a USB flash device. However the MR3020 Router only has a single USB port, so it needs to be expanded with a usb hub. The usb hub in the images below is small enough to fit inside the MR3020, and has a built in micro SD card reader. The SD card reader is essentially a usb SD card reader connected to the 4th USB port of the hub. Removing the casing and de-soldering the usb jacks are the first steps.

The USB port on the MR3020 needs to be removed to connect the USB hub. Short small gauge wires are suitable for connecting the hub. The ground wire needs to have a short amount of wire exposed above the board, the reason for this will become clear later. The USB port can be put back onto the MR3020 board but first the power and data lines must be connected to the pins. This will restore the functionality of the USB port however it will be internal connected to the USB hub so it adds the benefit of an internal SD carder reader.

The USB port can be reattached using only the mounting tabs, and the pins that go into the board can be bent outwards. This allows the wires attached to them to be routed along the board and attached to a free port on the USB hub. The ground pin of the USB port can be directly attached the short length of ground wire that was exposed from earlier. This saves having to run an additional line. The power wire should be run back to the hub in case the hub has the capability to shut off power to the ports.

This completes the required modifications to the interal hardware of the MR3020 router. An SD card can now be used to store videos, but OpenWRT needs packages to be installed and configuration to use the SD card reader and webcam, details will be given in part 2.

The logitech C170 webcam has a very narrow field of view, probably around 45 degrees. This is problematic when trying to monitor a room as some of the room is outside the field of view of the webcam. To increase the viewing angle of the camera lenses designed for smart phones can be used. These come with a metallic ring that a magnet on the lense sticks to in order to hold the lense in place. This can be used on the logitech webcam to hold these types of lenses in place. The two vertical bezels above and below the sensor need to be cut so that the lenses sit flush.

There are two types of lenses available, a wide angle lense and a fish eye lense. The wide angle lense gives about 120 degrees of viewing angle, while the fish eye gives 180 degrees. The downside of these lenses is that they distort the image.

The fish eye lense is to the right, and the wide angle is to the left.

I installed the two cameras in the lounge and kitchen, which you can see below.

Configuring the MR3020 routers to capture video is here.

No comments:

Post a Comment