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RE: Finally a cheap possible wearable solution?

got any sources for a 12v output switching regualtor?

-----Original Message-----
From: Jason Fox [mailto:]
Sent: Monday, February 24, 2003 12:07 PM
To: 
Subject: RE: Finally a cheap possible wearable solution?

This will certainly work but there are some considerations.  There are two
main types of regulators, linear and switching.

Linear regulators work basically by knocking down your input voltage to the
output voltage, this is done by turning the excess energy into heat ( =
wasted energy unless you are making a pocket warmer).  All linear regulators
have some amount of voltage differential between the minimum input and the
output, for example a 12V output you would have a minimum input of about
12.7V  This minimum input voltage is important because at this point your
output voltage becomes unpredictable, meaning that you really can only drain
your batteries down to the minimum input voltage.  Your efficiency on a
linear regulator is dependent on how much energy you waste by turning it
into heat.

A switching regulator does a DC-AC and then a AC-DC conversion process.
Because of this double conversion process (and some electronics inside) you
have a nice input voltage range (9-18V, 12-30V, etc are common) that can
actually be lower than your output voltage.  This is great for battery
applications when your batteries can discharge to a voltage level lower than
your electronics, you can use the full operation curve of the battery.
Their efficiency is almost entirely dependent on the design, 70%-95% are
common.  The down side is that they are usually much larger and much more
expensive.

For testing purposes you may be able to get by with a linear regulator, but
for any sort of regular usage you will be much happier with a switching
regulator.

- Jason W Fox
- Electronics Engineer
- (202) 404-3736
- SPG, ENEWS, Code 5707
- Tactical Electronic Warfare Division, Naval Research Lab
- Washington, DC

-----Original Message-----
From: Jeremy [mailto:]
Sent: Monday, February 24, 2003 15:44
To: 
Subject: RE: Finaly a cheap possible wearable solution?

"It might not hurt, though, to use a 13.2v or 14.4v battery, and run it
through a 12v regulator." - exactly what I was thinking.

-----Original Message-----
From: ben [mailto:]
Sent: Monday, February 24, 2003 10:47 AM
To: ; Jeremy
Subject: Re: Finaly a cheap possible wearable solution?

It may not be neccesary to regulate the voltage from the batteries, I'm
still
not sure.  Generally, 12v is roughly the same thing as 11v or 13v, so the
psu
will PROBABLY accept it (Bryan seems to agree with this), but we can't
really
know until somebody tries it.

It might not hurt, though, to use a 13.2v or 14.4v battery, and run it
through a 12v regulator.  This would probably allow you to discharge
further,
and still meet the 12v input of the psu.

My first step, once I have a working system, will probably be to hook a 12v
4AH NiMH battery (since I've already got the cells) directly into the psu,
and measure my uptime while performing something intensive, like a kernel
recompile.  If it's not satisfactory, I'll experiment with regulation and/or
other batteries.

-ben

On Monday 24 February 2003 14:07, Jeremy wrote:
> I was thinking about this this morning and I was
> think that I would have to build some sort of voltage
> "regulator", but I am not expert on batteries. even with
> the 12v power supply... (which I assume is expecting 12
> volts dc input) I would have to regulate the power from
> the bats. I can't remember the information from my basic
> electrical course.
>
> I am going to do the same thing as you.. I am going to
> start puchasing my parts run the puppy off AC till I get
> linux working. I will probably get it all together in a
> project box of some sort then worry about DC power.
>
> I will post my parts list after work tonight.

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