[MLB-WIRELESS] Solar components

[John Roberts]

Totally agree with the warning about 240 VAC inside various encapsulated
units, especially the double insulated ones, you may get a bite out of it
and still not trip the earth leakage breaker, if you have one.
BE CAREFULL!

	JR...


-----Original Message-----
From: owner-melbwireless at wireless.org.au
[mailto:owner-melbwireless at wireless.org.au]On Behalf Of John Dalton
Sent: Monday, 7 April 2003 12:14
To: melbwireless at wireless.org.au
Subject: Re: [MLB-WIRELESS] Solar components


It could also be worth looking at what is inside
any access point to be powered by a solar cell.

Typically wireless chipsets run off a 3.3V
power source.  The chances are that the access
point contains a linear regulator to drop
the voltage from 5V to 3.3V, resulting in
1/3 of your power being dissipated.

It could be worth removing the linear regulator
inside the AP and setting up the solar system
to generate 3.3V (or as close as you can get)
directly?  Also, look at disconnecting any
non-essential items such as LEDs.

Power dissipation for a chip is roughly linearly
related to clock frequency and quadratically
related to supply voltage (ie. P ~ f.V^2).
If the clock source for the AP's microprocessor is
independent of the WLAN local oscillator, perhaps
experiment with reducing the clock rate of the processor?
Perhaps also experiment with reducing the supply voltage
a little below specification?  Reducing the supply voltage
by a factor of 0.7 will halve the power dissipation
(though it will also slow the circuit down and may
stop it from working.  It should start working again
if supply is returned to normal, but don't blame me if it
doesn't.)  Keep in mind that it may not be a good idea to
reduce the supply voltage on the analog chips, as reduced
voltage might increase non-linearity leading to out of
band emissions.

Caveat:  I'm not sure what implications the above
may have for ACA approval of the device.
If using a switchmode regulator, heavy power supply
filtering may be required to avoid out of band
emissions.

To point out the obvious, there is some delicate electronics
inside an AP.  If you tinker with it, without knowing what
you are doing, there is a good chance you will break it.

Finally if your AP has anything more than twelve volts running
into it, you may *kill* yourself if you go poking around inside it.
(ie.  If you plug it directly into the mains, don't open it.)

Regards
John

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