AVR-Chat

Hi,

   Your method of checking voltage to determine cutoff would work 
somewhat for LiIon cells but not so well for NiMh.  NiMh have a pretty 
flat discharge curve and their charge curve is best served by monitoring 
temperature rise, the "peak" voltage of an NiMh is subtle and not always 
easy to catch without some pretty good charge circuitry.  I'd have to 
look up the optimal temperature rise to detect a full charge, I forget 
the details.  Check out battery sites to get more charge details.

DLC

On 3/14/10 6:45 AM, syberraith wrote:
> I'm unsure if I want to go straight to my final design in one step.  I might want to build a simple/limited version first.  For my most simple version I have the current being regulated by a linear regulator, and all the controller needs to do it turn it off when the system reaches a set voltage.
>
> More elaborate versions could include such things as pre-testing charge state, and automatic discharge of any remaining charge before charging.  However, my goal at the moment is just to get a simple one done and working.
>
>
>
> --- In AVR-Chat@yahoogroups.com, Philippe Habib<phabib@...>  wrote:
>    
>> I think that pretty much anything with an ADC would be enough.  You
>> could also get something with built in PWM so you could vary the
>> charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,
>> and 32HVA, HVB are designed to be chargers.  You could also go with a
>> general purpose device.
>>
>> Finally, although you can get by with a 6 or 8 pin chip for what you
>> want, you might want to go with more pins so you can dedicate pins to
>> the programming header.
>>
>>
>> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
>>
>>      
>>> I want to build a battery charger with a bit of intelligence, just a
>>> bit.
>>>
>>> I would like the charger to check the battery voltage every so
>>> often, one a minute at most, and if it has reached a set value, I
>>> would like the charger to shut it self off.
>>>
>>> I would also like charging to commence with a push of button to
>>> prevent a power interruption from starting a new charging cycle.
>>>
>>> To accomplish this I was wondering what device would be
>>> appropriate.  All it has to do is control a relay, and have a single
>>> ADC.
>>>
>>> Any suggestions?
>>>
>>>
>>>
>>>
>>>
>>> ------------------------------------
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>        
>>      
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
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>
>    

-- 
Dennis Clark
TTT Enterprises