Wall Warts at hand

[bonaventura]

so i was rumagging thru my stuff and found 3-4 wall warts lying around.

one is rated 9V 300mA,so im thinking to build some sort of filtering and regulating circuit after it,figuring it should be enough to power several pedals at least.

question no 1,since the wart is specced at 9V how to figure out max current available at the output (after regulator and filter caps)?

others were rated much less, 3.5V to 5.5V. these were my old  cellphone adaptors. yes, i use cellphones till they die on me (and also keep them,apparently).

question no 2,any ideas what to do with them? im thinking to power a signal generator or some other low voltage benchtop whatnots. ideas?

actually i have bought a 12V 500mA transformer and actually put together a PS circuit. but i wasnt confident enough assembling it after considering the risks. im gonna need to study more before i will but at the moment the above seems to be an alternative.

appreciate your input.thanks.

[crane]

Is the 9V adaptor AC? If it's not - how do you know that it's not regulated?
Anyway - simple 7809 circuit will do the trick. 7809 in TO220 package can handle up to 1.5A so the main PSU's current capabilities will be determined by your trafo which seems to be rated at 300mA, so there's your answer.
About those low voltage adaptors - I have a bunch too. Usually the lay in a box until I have to build a project with microcontroller. Then I give it (the PSU) away together with the project. Haven't found any other use for them.

[Jdansti]

Unfortunately, the 7809 and other regulators require the input voltage to be at least 2.5-3V above the regulated voltage.  You could regulate a 12V wall wart at 9V, but not one with an output of 9V. 

You could try the 9V wall wart without adding any conditioning and see what it sounds like. I'd also check the voltage while the effect is on.

[bonaventura]

Unfortunately, the 7809 and other regulators require the input voltage to be at least 2.5-3V above the regulated voltage.  You could regulate a 12V wall wart at 9V, but not one with an output of 9V. 

ah yes,i shouldve remembered that. thanks for reminding.

@crane,i just assumed it isnt anyhow ill try it out, see if luck hits.

lately whenener i see junk,i think what to salvage.there had been some desk relocation at the office and they replaced some cpu mice,phone and ethernet wires while they're at it.naturally i brought the junk home with me

ill think of something,i guess. in the mean time they stay hidden from the prying eyes of the mother in law.

[armdnrdy]

You might want to take a look at the LM317 voltage regulator. It's adjustable from 1.2 to 37 volts @ 1.5 amps. All you need is a trim pot and resistor and your good to go. If you research it a bit, I believe that there's another regulator that accepts a closer input voltage than the 7809. If you check your 9V wall wart, there's a good chance that it won't read right at 9 volts so a regulator will have a bit to work with.

[Pyr0]

It might still work with a 7809. Most 9v dc wall warts give out a lot higher voltage under light loads, measure the output voltage of the PSU - I bet it's more then 9v. . Then try putting say a 100 ohm resistor across it's output and then measure the voltage across the resistor, if it is still a bit more than 9v it should work fine for you.

[petey twofinger]

check this out , i made one that i really like , it was fun / and easy project ... i use it constantly too .

http://www.youtube.com/watch?v=MtiZRGfSGBI

absolutely quiet as a mouse , no issues what soever . i even can hard short it for like 2 seconds with  out popping the fuse / anything , which prolly isnt the best but . maybe i should get a much lwr value fuse . i did some a circuit cause i reverse polaritied it , like a goof !

honestly that can happen w/ any ps , so ... if i do lwr the fuse it should stop that from happening .

i wonder about puttting in rev pol protection diodes . hmmm how would that work ?

anyone ?

thanks ...