RE: [Project] Power requirements

[Keith Doxey <ukha@xxxxxxx>]

There was an article in the last issue of HomeAutomator that mentioned an
emerging standard for Powered Ethernet specifically aimed at uses like
this.

Basically a supply of 50V DC @ 300mA was available which gives 50x0.3 =
15Watts of power
15Watts of available power could be converted to 5V @ 3A, 12V @ 1.25A or
any
other combination where the total power did not exceed 15watts.

This does involve building a small Switch Mode Power Supply (SMPS) into the
device but some form of regulation would be needed anyway to overcome any
voltage drops. SMPS's are very efficient and dissipate little heat compared
to Linear Voltage Regulators.

Dedicated chips are available for the purpose but I would have to look up
suitable types.

Keith

-----Original Message-----
From: Dr John Tankard [mailto:john@xxxxxxx]
Sent: 29 May 2001 07:26
To: ukha_d@xxxxxxx
Subject: [ukha_d] [Project] Power requirements


Just thinking, how should we be providing power to our devices, the
lcd/keypad device will be installed in a two gang box, do most people
have two cat5 cables in ? We could use the single cat5 but i am
concerned about it becoming a non standard interface.

What do people think ?

Assuming we provide the power either on the primary ethernet cable or
a second cable, what voltage should we use, it should be comman for
all devices, so that one PSU can run all devices.

John




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