Kevin
There
is
no stabalization on board
The
voltage
supplied directly affects the power out of the
TX
Quote
from
info= “For max range use 16v power supply (absolute
Max)”
Mike
Sent from Home
-----Original
Message-----
From: Kevin Hawkins
[mailto:tivo@xxxxxxx]
Sent: Mon 02 Jul 01 10:15
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Howzat
work
then?
With a decent psu you
<should> be able to get exactly the
same quality as a battery. They are always invaluable anyway. M*****s
did d a very useful multi regulated unit once (probably when they
were still an electronics store rather than a toy shop).
Are there any other wires attached t
the
transmitter that go
t other electrical devices eg your audio sources - there is a
possibility of earth problems. With any transmitter good earthing is
essential. A wall wart should have a totally 'floating' output that
needs to be brought t chassis earth on the transmitter, as probably
do all other inputs. If the transmitter becomes unstable you would
see nothing.
. RF pickup is als potentially a
problem
but usually only at
high power levels. A ferrite core on each cable will help fix this.
It may all get better when it is in the metal (grounded) box.
I don't know how the frequency is fixed
in
the transmitter -
if it is crystal controlled or derived from a synthesiser then the
input voltage should have little effect however other methods may
well cause frequency instability if the supplied voltage varies at
all eg at 50Hz.
I assume als as you say it takes a wide
ranging voltage
input that there is on board stabilisation of the supply so I am
surprised you are seeing this problem. It would imply that the
troughs in the wallwart 12V supply voltage are dropping below the
regulators threshold yet it works fine on a 9V battery. Unregulated
wall warts tend to output way too much usually and rely on the
(known) load to reduce them t roughly the right level. Maybe the
drawn power is too high for the wall wart. What is the current
consumption of the transmitter ? I assume the psu feed and the 9V
feed used the same wires ? (not bypassing the regulator for the
battery usage ?)
Kevin
>I think that's the answer - I just did some testing with various
other
PSU's
>I had lying around, - one from a one-for-all IR repeater = same
result,
one
>from an old Sony Discman, = well it sort of worked! - the audio
transmits,
>but it is of a drastically lower quality than when running off the
battery.
>
>Does this mean the problem is due t poor quality rectification of
the
AC
>sinewave t DC? - could the el-cheapo wallwarts be doing
half-wave
>rectification only? If that's the answer, then presumably my Sony
Discman
>PSU must have been doing full-wave rectification, as the circuit
works
when
>using this one, but it's a bit worrying that the audio quality was
so
poor,
>- is this likely t occur with a "decent" PSU as well? -
I'd
hate t g out
>& spend £20 on a decent regulated PSU only t have the same
problem!
>
>Paul G.
>
>
>
>>From: Mike Griffiths <mike@xxxxxxx>
>>Reply-To: ukha_d@xxxxxxx
>>To: "'ukha_d@xxxxxxx'"
<ukha_d@xxxxxxx>
>>Subject: RE: [ukha_d] Howzat work then?
>>Date: Mon, 2 Jul 2001 09:43:28 +0100
>>
>>I think Keith has the answer then as it does say Regulated PSU
under
>>circuit
>>testing :-(
>>I must admit I would have pugged up a wallwart t o
>>
>>Mike
>>
>>Sent from Home
>>
>>-----Original Message-----
>>From: Paul Gordon [mailto:paul_gordon@xxxxxxx]
>>Sent: Mon 02 Jul 01 09:38
>>To: ukha_d@xxxxxxx
>>Subject: RE: [ukha_d] Howzat work then?
>>
>> >Paul
>> >Does the wall-wart work anything
else?
>>
>>Tests OK with the spare bulb from my Maglite.... (in fact I've
got
a blind
>>spot right in the middle of my vision 'cos it was s
bright!!!)
>>
>> >What happens if you run it at 9v?
>> >
>>
>>The same, - the LED on the PCB comes on as it should, so the
circuit has
>>power t it, but ****-all is being transmitted...
>>
>>Paul G.
>>
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