| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2204.1 | | SUBURB::FRENCHS | Semper in excernere | Thu Jan 13 1994 14:57 | 13 |
| Assuming at is a 5 watt output then 500 ma should do. If 25 watt
then 2 amp will be more likely. Go for a 3 to 5 amp pwr supply
then there should be no problems at all. If however you wish to
upset the neighbours with 300 watts of noise a cool 25 amp may
be just enough to keep the fuses from popping.
These figures are best guesses using the formula I = P/V ie
currant = power divided by voltage (12v). I could be totally
wrong and will accept better judgement.
Simon
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| 2204.2 | | FORTY2::PALKA | | Thu Jan 13 1994 15:35 | 11 |
| I would think you would need at least twice the output power of the
radio. Car radios are not designed to be ultra efficient, and the
cheapest way of building an amplifier will result in the same amount of
power being dissipated in the amplifier as in the speakers.
So if the radio is 2 outputs at 5W then you need 20W of input power, or
about 2A. If the radio has a fuse, or if the manual tells you what fuse
to use, then you know that you will not need more current than the
fuse rating.
Andrew
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| 2204.3 | | CHEFS::TAFF::Wob | Robert Screene, UK Finance EUC | Thu Jan 13 1994 15:38 | 6 |
| Infinity just launched a Class D car amp into the UK car market.
Apparently Class D is much more efficient, running very cool, but
it's fiendishly complex to build for the car environment.
Rob.
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| 2204.4 | I've always used a car battery charger | SUBURB::VEALES | More undercompensated | Thu Jan 13 1994 18:53 | 1 |
|
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| 2204.5 | Thanks | ESSB::DOODY | | Fri Jan 14 1994 14:12 | 15 |
| Thanks a lot ,
I reckon that About 2amps should do the job!
I tried an old scalextric transformer last night (1 Amp)
and it worked better but the tape was slow at all but very low volume.
re -3 : I never thought about checking the fuse rating
it was the obvious thing to do!
re -1 : Yes the trusty battery charger is what Im using at the moment
charger --> batterg --> radio/cassette
Brian.
|
| 2204.6 | | FORTY2::PALKA | | Fri Jan 14 1994 15:16 | 13 |
| The scalextric transformer must be providing enough current, or its
safety cutout would have operated.
I think you probably need something with a better output waveform The
scalextric transformer will probably not have any smoothing capacitors,
and the radio is probably designed to run from a fairly smooth DC
supply. Its own supply decoupling capacitors would not be capable of
holding the voltage during the gaps in the output of the transformer.
You might improve things by putting a 2000 microfarad capacitor (at
least 25V) on the DC supply to the radio. (I'm surprised you did not
notice a lot of hum)
Andrew
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| 2204.7 | | WOTVAX::63872::Craig | Hello! | Tue Jan 18 1994 15:47 | 8 |
| A regulated 13.5volts 3amp power pack available from Tandy/Maplin etc will
do the trick. About 20 quid.
By the way, if you're using the scalextric transformer and the tapes too
slow, try using one of the hand controlers....
8-) ..Craig
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| 2204.8 | humm... | CMOTEC::JASPER | Stuck on the Flypaper of Life | Wed Jan 19 1994 16:40 | 7 |
|
I hope that the amplifier circuits dont pick up too much hum from the
transformer...
Tony.
|