Help! Universal Adaptor Question

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Hi, I just bought a portable handheld tv, the Casio TV-970, and want to
purchase a universal adaptor for it.
The universal adaptors I've seen have different ratings, from 350mA, to over
1000mA.
The specifications on the user guide says that it runs on 6 volts, and the
power consumption is approiximately 3.1W.

How much mA do I need?

Regards,
Patrick



Re: Help! Universal Adaptor Question



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over


P=V*I so I=P/V

P is power in Watts
V is voltage
I is current in Amps (1000mA1A%)

Watch the polarity!!!!

You can use a power adapter with more current but be warned that most
of these cheap power supplies are half wave rectifiers with a capacitor.
This means they are NOT voltage regulated.  Measure one that is not
loaded and verify that the output voltage is higher than stated.





Re: Help! Universal Adaptor Question


it's 500mA btw, buy a $20 digital multimeter then you can measure things
yourself.

:
: > Hi, I just bought a portable handheld tv, the Casio TV-970, and want
to
: > purchase a universal adaptor for it.
: > The universal adaptors I've seen have different ratings, from 350mA,
to
: over
: > 1000mA.
: > The specifications on the user guide says that it runs on 6 volts,
and the
: > power consumption is approiximately 3.1W.
: >
: > How much mA do I need?
: >
: > Regards,
: > Patrick
:
:
: P=V*I so I=P/V
:
: P is power in Watts
: V is voltage
: I is current in Amps (1000mA1A%)
:
: Watch the polarity!!!!
:
: You can use a power adapter with more current but be warned that most
: of these cheap power supplies are half wave rectifiers with a
capacitor.
: This means they are NOT voltage regulated.  Measure one that is not
: loaded and verify that the output voltage is higher than stated.
:
:
:
:


Re: Help! Universal Adaptor Question





You can use a power adapter with more current but be warned that most
of these cheap power supplies are half wave rectifiers with a capacitor.
This means they are NOT voltage regulated.

*** Er,where did this nonsense come from.Half wave???????????????

Brian Goldsmith.




Re: Help! Universal Adaptor Question



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Some have a half wave rectifier some have full wave, almost all are crap
and none of that type are voltage regulated.  Cut some open and look or
just scope the output.  The point is that he should not use that type.








Re: Help! Universal Adaptor Question



"Lord Garth"
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**  Some adaptors use two diodes, others have four diodes or a bridge
rectifier -  in all cases that is full wave rectification.





..............    Phil






Re: Help! Universal Adaptor Question


WHICH ONE IS HALF WAVE?

If a device has an onboard voltage regulator then the requirement for
the power supply to do the same is false economy and inefficient.

:
message
: >
: >
: >
: > You can use a power adapter with more current but be warned that
most
: > of these cheap power supplies are half wave rectifiers with a
capacitor.
: > This means they are NOT voltage regulated.
: >
: > *** Er,where did this nonsense come from.Half wave???????????????
: >
: > Brian Goldsmith.
: >
: Some have a half wave rectifier some have full wave, almost all are
crap
: and none of that type are voltage regulated.  Cut some open and look
or
: just scope the output.  The point is that he should not use that type.
:
:
:
:
:
:
:


Re: Help! Universal Adaptor Question



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I'd look at the output on a scope.  If there were no capacitor the wave form
would have an area of essentially 0 volts between pulses whose frequency
is equal to your mains frequency.  The near zero area is 1 half cycle wide.
This uses one rectifier.

If full wave,  the pulses are at twice your mains frequency.  This uses two
rectifiers.

There is also the full wave bridge configuration.  This is used when a
center tap exists.  This uses 4 rectifiers.

A regulated DC power supply will simply offset the sweep if the scope
is DC coupled.  There should be no sign of the mains AC in the trace,






Re: Help! Universal Adaptor Question



"Lord Garth"
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 **   No regular adaptor on sale is like this.


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 **   More stupid errors   !!

 The FULL WAVE circuit use two diodes and a centre tap.

 A"bridge rectifier" uses four diodes and no need for a centre tap.



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 **  Any supply with a filter cap will ALSO show pure DC with no load.


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.............   Phil













Re: Help! Universal Adaptor Question



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How odd, I have one.  I bought it because the case screwed together allowing
me to remove the diode and cap as these were inside the 70's vintage Corvus
digital clock already.  I needed low voltage AC.  Its been running since
1979
with only 2 down intervals so far due to failed caps.  Clearly, it was one
of
a large quantity of injection molded power supplies so 'regular' is the
qualifier.  Maybe it's not regular or common but it is sold.

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The full wave bridge would have a center tap if it was part of a bipolar
supply....I'll mark that one half off.






Re: Help! Universal Adaptor Question



"Lord Garth"  =  congenital idiot
 "Phil Allison"
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**  Blatant lie.


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 **  No cap at all in the one you described above   -   wanker.


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 **  What a desperate bloody liar.






...........     Phil







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wave

I didn't see you standing there in my home 26 years ago!
You're an absolute superman.

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As if you saw me remove said cap...you know, cylindrical device
about 3/4" in length, radial leads and labeled 100uF 16V.  Sorry,
wanker was not the manufacturer.

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uses
a

How would you build a bipolar power supply that used a full wave bridge
and a transformer?

I'm always willing to learn.  You can post your schematic to A.B.S.E.





Re: Help! Universal Adaptor Question



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1
when
bipolar

Easy, transformer with centre tapped secondary.  Common rail connected to
the centre tap.
Bridge rectifier connected to ends of windings.  Filtering caps connected
between + and - outputs
of the bridge to the common rail.  Easy as... :)

Check ou the circuit at -
http://emsyl.ece.ua.edu/dawson/App/bipolar%20pwr%20supply%20tech.pdf
The left hand side of the circuit up to capacitors C1 and C2 (before the
regulator ICs)
is an example of a simple bi-polar power supply.  The common rail is the
junction between
the two filter capacitors C1 and C2 which connects back to the centre tap
(6) of the
transformer.


Cheers,
Alan

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<snip>

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when a
bipolar



Exactly!  But other seems to think that me a "...desperate bloody liar"
However, I know he knows better.  I really could not possibly care less.  As
it
is close to tomorrow here, G'day and goodnight from this side of the
terminator.




Re: Help! Universal Adaptor Question



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is
<snip>
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Appears you've missed the word IF above....  *yawn*
Good day.





Re: Help! Universal Adaptor Question



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** When analogue TV is switched off in 2008 -  that toy will cease to
function.


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** You need an  700  - 800mA rated  **regulated**  adaptor of the correct
polarity.

     Buy the Casio one if you have any sense.





.............   Phil



Re: Help! Universal Adaptor Question


You might still be able to watch via a VCR (if they still have VCR's in
2008)

Buy the way wouldn't the "TV digit box" have a analogue output so you can
still use the old analogue TV's until they suff it.





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** When analogue TV is switched off in 2008 -  that toy will cease to
function.




Re: Help! Universal Adaptor Question



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**  Sure  -  just shove one in your back pocket.


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**  That Casio is a tiny, portable TV  -  you sheep shagging, top posting,
anencephalic.

     It will cease to function as a portable !!!!



............   Phil




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yeah whatever, as if theyre actually gonna turn it off. the public
whinge will see that extended

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wotta wanka why would you have less "sense" not buying the 'casio one'
switchmode 6v 1amp jobs from dickys would be more than adiquate, better
v-reg and most probably cheaper.... pffft buy the casio one? you reject!!!!

Re: Help! Universal Adaptor Question


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Patrick, get one with *at least* 500mA rating. I'd go for about 750mA to
give some margin, esp. since it appears you're in a warmer climate.

Ken



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