If I ever go into space I want Ed and PCBman in the capsule! ...Guys,
why is that red warning light flashing above the console that says Life
Support?
>>> david.humphreys_at_honeywell.com 05/30/02 02:42PM >>>
Ed said:
> I've got a camera that is also a "AA" battery killer,
> but if you understand how the camera works, you'll
> realize that the batteries aren't really dead!
> The older cameras use TTL circuitry.
Transistor Transistor Logic
> This requires a minimum of 5volts.
Ooopps! Standard TTL Vcc is 4.75V - 5.25V
> 4-"AA" batteries gives 6volts.
> Once the combined power of the batteries drops below 5
> volts,
Make that 4.75V.
> then the camera will no longer work...
That is why they have a buck/boost regulator in them.
When the supply is above 5V, the regulator 'bucks' the
supply (careful with the spelling there) down to 5V.
When it is below 5V it 'boosts' it up to 5V.
> but, it
> doesn't take a math genius to figure that with 4-"AA"
> batteries at 1.5volts per battery. To drop from 6volts
> to 5volts means that each battery looses .25volts
> (that's a quarter of a volt) That means that the
> battery still has 80% of it's capacity! This is plenty
> for any other device that uses "AA" batteries. Things
> like the Newt will run for weeks on old camera
> batteries! My SLR flash unit gives me almost a hundred
> flashes....my pager runs for 3 weeks on one of these
> old camera batteries!
I don't doubt that you can recycle the batteries in other
devices. They are either less demanding in power or have
a vastly different power need.
Fact is, an alkaline cell will drop its' terminal voltage
very rapidly as the internal resistance goes up. If I look
at the discharge curve for a typical AA cell and assume
250mA as a load, the terminal voltage will reach 1.25V
in 2.5hrs (based on 5V TTL min.) or 4hrs (based on 4.75V min.).
A Buck/boost circuit would extend this time even longer.
> So, don't throw those old camera batteries away! Just
> because your camera can't use it, doesn't mean that
> it's dead to everything else!
> .Ed
This is true. Your flash works because an inverter circuit
inside charges a capacitor. The circuit, to a point, doesn't
care what the input voltage is. It just takes longer to charge
if it is lower.
The pager probably uses flea power unless the vibrator motor
is activated. Even then, it is fairly small.
PCBman
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