Laptop power supply for pedals?

[hilbi]

Anyone tried a laptop power supply as power source for your pedalboard?

Laptop powersupply is basically 18 volt dc, does anyone know how to get 9 volt out of this?

[aron]

I was thinking about this once when looking at my Powerbook adaptor.

Use a voltage regulator to get the voltage down to a stable 9V. Radio shack LM317

also LM7809 etc...

http://www.southwest.com.au/~jfuller/electronics/regulators.htm

[hilbi]

Thanks for the info aron, I read through the article and got a question on that.

The input of a LM7809 needs to be 2 a 3 volt higher then the output, the lm7809 can take up to 30 volt, so if the input is higher then say 12 volt heatsinking needs to be applied.

In case of the laptop's 18 volt, how big should that heatsink be?

[Gilles C]

I also depends on the current used by the circuits.

If the 7809 gets 9V to loose at 1A for example, it's 9W that it will need to dissipate.

Here is an example of a 10W heatsink.

http://www.referenceaudiomods.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=HS_QR_10W&Category_Code=MISC&Product_Count=8

Going from 18V to 9V at 1A would be the same as going from 27V to 9V at 0.5A

That was the not very technical explanation.

For something more technical:

http://www.eleinmec.com/article.asp?20

Gilles

[skumbeg]

I bought one of these and was thinking about making a 9v supply out of it.  I figured it would work fine.  I have heard that they don't have a lot of ripple.  Maybe it wouldn't need a regulator??  I dunno  :?
http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=PS-1211&type=store

[Ge_Whiz]

Buy a 3-12V variable regulated power supply. 300 mA units are about £7, and 1A units about £12 in the UK. No hassle, and so much cheaper than your next pedal.