Canon A40 - Polarity of AC Adapter?

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Edythe Woodruff

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Jan 16, 2003, 9:51:49 AM1/16/03
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Canon sells an AC Adapter for the A40 camera, for about $65 ... this seems
like a lot for an adapter. Thus I'd like to use another brand of AC adapter
on this camera. The camera connection is labeled "DC IN 4.3 volts".
However, it does not specify the polarity. (I don't want to just assume
that the center connection is positive, for fear of possible damage to the
camera.)

Does anyone know the polarity of this connection?

Thanks, Edythe


Mike Blowers

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Jan 16, 2003, 11:50:49 AM1/16/03
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I really wouldn't try a different adaptor, other than the manufactures
own... appart from the polarity issue, there is the very important and often
overlooked issue of output, not in voltage, but in amp's (usually stated as
"ma")... If you overload the amp rating you can do more damage to the camera
than you can if you get the voltage wrong.

One posibility though, is to ask a shop if you can see the actual adaptor,
make a quick mental note of the rated output in amps (it's usually stated on
the label)... and just make sure your other adaptor is the same (or very
close)... then worry about the polarity.

Mike.


"Edythe Woodruff" <EdytheW...@comcast.net> wrote in message
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Rayan Rawa

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Jan 16, 2003, 1:33:31 PM1/16/03
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Mike Blowers wrote:
> I really wouldn't try a different adaptor, other than the manufactures
> own... appart from the polarity issue, there is the very important and often
> overlooked issue of output, not in voltage, but in amp's (usually stated as
> "ma")... If you overload the amp rating you can do more damage to the camera
> than you can if you get the voltage wrong.
>
> One posibility though, is to ask a shop if you can see the actual adaptor,
> make a quick mental note of the rated output in amps (it's usually stated on
> the label)... and just make sure your other adaptor is the same (or very
> close)... then worry about the polarity.
>
> Mike.


Allow me to correct you.

He can use any source that has the same rated voltage, connector
polarity, and *at-least* the current rating (mA) of the original adapter.

A higher current rating can NOT damage the camera because:

the current rating on the label is the maximum current the adapter can
supply. It is NOT the the current that would flow when you connect it to
the load.
The actual current flowing depends on the load (camera) resistance. The
camera has a fixed resistance. The supply has a (somewhat) fixed
voltage. The current flowing = supply_voltage / camera_resistance.

In other words, the camera will "take" what ever current it needs, not
more. Just make sure the supply can source by
current_rating >= current_rating of the original supply.


Regarding teh voltage, I would NOT try any higher voltage.


RR.

p.s. i take no responsibility of course ;)

pushbutton

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Jan 16, 2003, 2:56:25 PM1/16/03
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Hi Edith.

The answer to your question is Centre Pin = +

I bought an Adaptor from Jessops in the UK and it works just fine. It comes
cpmplete with a whole host of connectors and variable output voltages.

Try www.jessops.com for more info

Regards

Pushbutton


"Edythe Woodruff" <EdytheW...@comcast.net> wrote in message
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Steve Roys

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Jan 16, 2003, 4:40:06 PM1/16/03
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On Thu, 16 Jan 2003, Mike Blowers wrote:

> I really wouldn't try a different adaptor, other than the manufactures
> own... appart from the polarity issue, there is the very important and often
> overlooked issue of output, not in voltage, but in amp's (usually stated as
> "ma")... If you overload the amp rating you can do more damage to the camera
> than you can if you get the voltage wrong.

Like an acquaintance of mine who asked a seller at an electronics show
"How many amps is that capacitor...?" But then, he also seriously
believes that spam is an alien plot and that the US has colonized Mars...
;-)

More amps is just fine. As long as the transformer is the proper voltage,
the camera won't suck in any more electrons than it can use. Less amps
would likely be as non-dangerous as less volts (old batteries). More
volts is a definite no-no, as you could easily end up with an expensive
paperweight when the doohickeys attached to the higher voltage are now
drawing more amps (=V/R) and decide to go into catastrophic thermal
failure (=I^2 * R).

Steve

Edythe Woodruff

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Jan 16, 2003, 8:37:40 PM1/16/03
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Thanks! The link was very helpful. I think I will follow the suggestion of
having a good supply of NiMH rechargable batteries and see whether it turns
out that I really need the adapter also. I do not plan to take pictures
with the adapter attached, but I know I need the batteries and charger.
"Rick" <nos...@earthlink.net> wrote in message
news:b06otk$m0016$1...@ID-82690.news.dfncis.de...

> "Edythe Woodruff" <EdytheW...@comcast.net> wrote in message
news:caycnQ2Iipg...@comcast.com...
> It's center positive. Read additional info here (link may wrap):
>
http://forums.powershot-a.com/showthread.php?s=491372228f12b357bbb4f03a227ad
8d0&threadid=2396
>
> RickW
>
>
>
>


Mike Blowers

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Jan 17, 2003, 5:11:49 AM1/17/03
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Ooops... Appologies for my mis-leading post.... I stand corrected :-)...
Thank-you.

I was told about the amp issue a while ago.. obviously I've just passed on
some bad info I got.

Mike.

"Rayan Rawa" <re...@NG.plz> wrote in message news:3E26FAFB...@NG.plz...

NickS

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Jan 21, 2003, 6:20:21 PM1/21/03
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FYI -

The A40 manual (available online from www.powershot.com) lists the
output rating of the AC Adapter at 4.3v and 1.5 A.

The amp rating is higher than I'd expect, and is likely higher than
many typical "wall-wart" adapters which are in the 500-1000 mA range.
As mentioned in other postings, if you choose another adapter, be sure
it's rated for at least 1.5 A. My guess is that this higher rating at
least partially explains the higher cost of the Canon adapter.

- Nick

"Edythe Woodruff" <EdytheW...@comcast.net> wrote in message news:<hr6dnSZCk8N...@comcast.com>...

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