Extending the Distance between a Camera and the Controlling Host System

Download PDF - Extending_the_distance_between_camera_and_host

Introduction

A variety of configurations are available for extending the distance between Point Grey cameras and host controllers beyond the maximum recommended 4.5-meter cable length specified by the IEEE-1394 standard. Depending on how far from the host system you want to mount your camera, the following components can be used to configure a solution:

• Standard 4.5-meter cable
• 10-meter cable
• Multiple cables connected to repeaters
• Category 5 cables connected by Point Grey Long Distance Repeaters (LDRs)
• Category 5 cables connected by repeaters from outside vendors
• Optical cables connected by repeaters

In the following section, each solution is compared for speed, distance, and cost. The remainder of the article explains the solutions in more detail and provides information about how to obtain parts.

Solution Comparison

The table below summarizes the solutions for camera-to-host extensions at different distances. Following the table, each solution is described in more detail.

4.5 Meter Solution

The maximum recommended distance for connecting to an IEEE-1394a and 1394b device is 4.5 meters. As part of their development kits, most Point Grey cameras ship with a 4.5-meter cable. Additional 1394a and 1394b cables can be purchased directly from Point Grey Research through our FirePRO™ line of accessories.

10 Meter Solution

Point Grey Research provides a 10-meter cable for covering a longer distance between 1394b devices beyond the standard 4.5 meters.

30-36 Meter Solutions

You can use repeaters with 1394 cables in a daisy chain for coverage beyond 10 meters. If 10-meter cables are used, we recommend using a maximum of two repeaters, which allows for three cables, or 30 meters. If 4.5-meter cables are used, the 1394 specification allows for 16 cables to be daisy chained for a maximum length of 72 meters. However, we recommend that the number of repeaters not exceed seven, which allows for eight cables, or 36 meters. As indicated by the chart in Section 1.5, this solution can become costly and impractical as the number of hops increases.

An external power supply is not always necessary when using only a single repeater. However, to ensure adequate power to the camera, we recommend powering the repeater in all cases with an 8-30 volt AC-to-DC external power supply (ideal voltage is 12V). Consult your camera's Technical Reference or Getting Started Manual for individual camera power requirements.

Point Grey Research sells the following 1394b repeaters and power supplies. Note that the 2-port repeater does not accept external power.

• * The 2-port repeater does not accept external power.

For more information about powering the camera, maintaining a connection, or using repeater-hubs to connect multiple cameras to a single host controller, consult the applicable knowledge base articles in Section 1.8 Related Knowledge Base Articles, below.

74 Meter Solution

For distances beyond 36 meters, you may find solutions with other vendors. For example, a pair of Newnex FireNEX-CAT5 S400 repeaters claims to work with a 65-meter Category 5 cable, but at a 1394a data rate of 400 Mbps. These devices are configured in a manner similar to what is described in the following section. With the addition of two 4.5-meter cables connected to the camera at one end and the host at the other end, the total distance is 74 meters.

 100 Meter and Longer Solutions

To cover a 100-meter distance, Point Grey Research offers Long Distance Repeaters (LDRs), which connect to a Category 5 cable, and provide an 800Mbps rate across the full distance. The LDR has two ports to support a pair of cameras or a camera array. To ensure adequate power to the camera, we recommend powering the LDR that connects directly to the camera with an 8-30 volt power supply. A pair of LDRs must connect directly to each other. Routing an LDR through a switch device is not supported.

In addition to the configuration above, Point Grey has successfully tested daisy-chaining two pairs of LDRs, connected by a 4.5-meter cable. The LDR furthest from the host system supported three Grasshopper cameras (two cameras daisy-chained). This configuration, shown below, can cover a maximum distance of 218 meters.

The LDR is available directly from Point Grey Research. As indicated by the chart in Section 1.5, it is a cost-effective solution for achieving a 1394b data rate over a long distance.

An even longer solution may include a pair of optical repeaters, connected with an optical cable. The Newnex FireNEX800 optical repeater claims to work up to 500 meters, and retails for US$ 798.

Synchronization Considerations

The devices described in this Technical Application Note do not interfere with the ability of multiple Point Grey cameras to auto-synchronize. For more information about auto-synchronization, consult your camera’s Technical Reference Manual.

USB Cameras

The maximum cable length between any USB node (e.g. camera to USB, USB to hub, etc.) is 5.0 m, as indicated by the USB specification. For more information about extending distances between USB cameras and host systems, refer to this FAQ on the usb.org website.