AVR-Chat

Hi Cobb,

I probably didn't explain myself too well, plus my typo where I said 
I wanted 3V from the converter, I really meant 5V.

I have 4 batteries (this is the maximum room I have in my case). The 
printer runs from 5V and consumes 3.5A peak. The idea was to connect 
2 pairs in series to give 3V, and then connect the 2 x 3V cells in 
parallel to double the capacity.

As this is a hand held device I do not want to connect all 4 in 
series and use a regulator to bring it down to 5V, thats a waste of 
power as I want maximum operating time from the device. 

Others have raised the issue of internal resistance which I had not 
considered, and suggest NiMh batteries which would mean I would have 
only 2.4V max to boost to 5V.

Cheers
Col 

--- In AVR-Chat@yahoogroups.com, "Cobb, Quentin" <quentin_cobb@t...> 
wrote:
> I don't get it.  You have four AA batteries, so you have 5v if you 
run them
> in series. You want 5v to run the printer.  Why do you need to 
convert
> anything?
> 
> 
> 
> 
> 
> -----Original Message-----
> From: C Sizer [mailto:aussiecol39@y...] 
> Sent: July 30, 2004 8:17 AM
> To: AVR-Chat@yahoogroups.com
> Subject: [AVR-Chat] DC-DC converter
> 
> 
> Hi guys,
> 
> I am designing a university project, a hand-held printer using the 
> AVR and a small thermal printer. For portability I want to use 4 x 
> 2300mAh AA batteries in serial/parallel to provide me with 3V.
> 
> The printer runs on 5V but consumes over 3.5A peak, so I require a 
DC-
> DC converter circuit (or at least a starting point) to provide 3V 
at 
> 5A peak.
> 
> Has anyone designed anything like this, or can give me some advice? 
> Maybe someone has an idea for a better battery for me to use?
> 
> Cheers
> Col
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> - Scanned for viruses by MessageLabs on behalf of Tesco 
Corporation -
> 
> - Scanned for viruses by MessageLabs on behalf of Tesco 
Corporation -