Power adaptors - using ones from old kit with exisiting kit

[beastman]

Probably not the normal kind of question asked around here......
Just wondering if anyone can confirm this. I acquired a computer scanner but it didn't have its original power adaptor.
Rather than buying a replacement I found an old laptop power adaptor (the laptop has long since been condemned) and this has the same connection as the scanner. Now the scanner only needs 15 Volts @ 1 Amp but the laptop adaptor is rated at 19V @ 6.3A. So the scanner needs up to 15 watts to run and the adaptor is rated to provide up to 119.7 watts but it works fine, at least it seems to, with the scanner. So does this mean that the old laptop adaptor automatically adapts to the power needed? Is this at great risk of damaging the scanner? Is a shed load of power being wasted?


thanks

 

[Guest111]

A unit will only draw the amount of current it needs,however you are giving it 4 volts over what it should have,it may work fine for a while but you could fry it long term.Best work out what is cheaper,buy the right adaptor now or a new scanner later.

 

[RogertheBodger]

Your scanner will take what current it needs to work, so no power wasted. The voltage has increased by almost 25% which is probably outside normal tolerances, although it's working it could be suffering slow damage from the over voltage and may fail eventually, I would be happier with the correct power supply.

 

[RogertheBodger]

Lol Phil.

 

[DPG]

Agree with the answers above - the extra current availability isn't a problem, but I definitely wouldn't exceed the voltage input by 4 volts. Mind you, the scanning shouldn't take as long. That's ajoke by the way Daz

 

[beastman]

thanks guys - so a general rule is stick close to the original voltage and the amps difference isn't a big deal?
I know its a basic question for you lot but I know naff all about these things - why is the voltage more crucial - my naive guess would have been the overall power (volts x amps) as the more important thing.

 

[RogertheBodger]

Current rises with the voltage across the same value of resistance, too much current = too hot, pffffft.

 

[itselectric]

In this case think of voltage as pressure. Too much pressure and something's got to give.