| Backup power on this network: |
 | Is power rated to exceed total devices loaded | |
| Batteries are regularly tested, otherwise 100% charged | |
| Secondary not primary power, AC power is still available if a UPS fails | |
| Tested running servers and routers for 30 minutes without AC power |
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|
| For this network's two main servers a higher-end domestic unit has proven sufficient. A 'server farm' might prefer larger
rack-mounted UPS's for mission-critical hardware. In the home many older or smaller models, less than 800 VA, are sufficient
to protect a small computer. Replacing the batteries of older UPS's is often cheaper than shelving a unit you know was working for
a high-powered replacement that might be 'over the top' compared to its actual requirements.
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| Power control for better connectivity
|
| A UPS can also be used to power devices up or down under certain conditions, if its drivers include a controller. Even
if your UPS doesn't offer advanced options, there are other affordable devices that will do the job, such as the Ocean Controls KTA-223 (pictured).
|
| This method works with a controlled UPS or a Relay Controller connected to the power input of an ADSL router. Write a shell script to:
|
|
| Poll your ISP's DNS for the address of a well-known site, | |
| Do nothing if an address results. Connection is OK. | |
| Disconnect power to the router for five seconds if the poll fails. | |
| Repeat these steps every 30 minutes or so, as a scheduled procedure. |
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|
| Networked power control
|
| So far things will work with just a USB-serial controlled UPS or power relay. The
KTA-223 can also be fitted with an Ethernet 'Shield' enabling control by several computers with existing network
hardware. For mission-critical networks this means added protection in the event of failure of the first computer
connected to the controller. Many UPS vendors ship network controllers with higher-end models for the same reason.
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| A new program or 'sketch' had to be adapted from existing open-sources to get the controller to respond to network commands,
and testing with a 'web-page' interface (my own code, works in IE/Mozilla). The web interface does not run on a computer or server,
but comes directly from the controller (using basic 'read char/send char' routines). A standard HTML form is used to
switch Relays & Inputs.
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