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Home > Archive > Electrical Engineering > October 2007 > If a camera needs 7.9v, can I use a 7.5v adapter or a 9v adapter?
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If a camera needs 7.9v, can I use a 7.5v adapter or a 9v adapter?
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| postitnote 2007-10-18, 9:25 am |
| I have a video camera.
I can't find the power lead.
A replacement can not be purchased anywhere now.
I am trying to get a universal adapter to power the camera.
The camera says it needs a 7.9v DC power supply.
Would I get away with a 7.5 or higher than 7.9v supply?
The reason I ask is that I can't find ANY universal power supplies
that output at 7.9v.
Any advice on this is highly appreciated!.
Kind Regards,
David
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| Andrew Gabriel 2007-10-18, 1:25 pm |
| In article <1192711349.003913.155370@t8g2000prg.googlegroups.com>,
postitnote <dgeere@wpminternet.com> writes:
> I have a video camera.
> I can't find the power lead.
> A replacement can not be purchased anywhere now.
> I am trying to get a universal adapter to power the camera.
> The camera says it needs a 7.9v DC power supply.
> Would I get away with a 7.5 or higher than 7.9v supply?
>
> The reason I ask is that I can't find ANY universal power supplies
> that output at 7.9v.
>
> Any advice on this is highly appreciated!.
7.5V would be a safer bet than 9V.
Given you don't know if this was a regulated or unregulated
supply, make sure that you get a regulated 7.5V supply, or
it will probably be over 10V off-load, which might damage
the camera.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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| postitnote wrote:
> I have a video camera.
> I can't find the power lead.
> A replacement can not be purchased anywhere now.
> I am trying to get a universal adapter to power the camera.
> The camera says it needs a 7.9v DC power supply.
> Would I get away with a 7.5 or higher than 7.9v supply?
>
> The reason I ask is that I can't find ANY universal power supplies
> that output at 7.9v.
>
> Any advice on this is highly appreciated!.
>
> Kind Regards,
> David
>
D1 D2 -----
+12 --->|--->|---+---in|LM317|out---+------+-----> + 7.9
| ----- | | +
[.1uf] Adj [240R] [10uF]
| | | |
| +---------+ |
| | |
| [1276.8R] |
| | |
Gnd -------------+--------+----------------+-----> Gnd
The above circuit will provide ~7.9 volts at up to
1.5 amps if you put the LM317 on a good heatsink, but
I would recommend adding a pass transistor if the
camera needa more than 1 amp. You can use a 1200 ohm
and a 75 ohm in series for the 1276.8R resistance,
and the output voltage will be 7.89, which will be fine.
Ed
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