3 terminal regulator question

[scabrabbit]

I'm really totally new to building pedals, so I have a bit of a dumb question. How do I wire a 3 terminal regulator?

My circuit (a simple PT2399 delay) works on a 9v battery, but I want to convert it with my DC adapter. Can I just put in the regulator?

[CynicalMan]

Take a look at the data sheet of your regulator. There should be a sample circuit.

[darron]

indeed you should always read up on the IC's datasheet as it gives you all the info you need and usually even some sample circuit diagrams... but don't worry, it's not hard! (:

i'd probably use a fixed value +9v 7809 regulator. take a look in google for a datasheet. what are the specs of your DC adaptor? i assume that you already know that it's no regulated and that's why you want to put a regulator between. the input voltage of a regulator should usually be around 3 volts higher than the output, so an ideal DC input would be 12V to give 9V out. hence why i ask about your power adaptor.

3 pin regulators are simply one pin for DC in, one pin for DC out, and one pin for common ground. then you'll need a filter cap of around 220uF before and after to keep things running smooth. then if you want to get fancy (and it IS technically beneficial) you can add small value RF filters, and diodes here and there to protect the regulator (see diagram in datasheet). id also consider a large diode like a in4007 AFTER the output caps reversed across the rails incase you accidentally ever short the positive and negative one day.

you can do it with a AC supply easily too. with a 9VAC supply, followed by a rectifier you get around 12VDC which you can then filter and regulate.

hope this helps....

[scabrabbit]

Thanks, that does help! I haven't actually bought the regulator yet because I felt hopelessly lost as to what to do/which to get.

I have this boss adapter: http://www.musiciansfriend.com/product/Boss-PSA120-Adapter?sku=151370

But it may not be usable in this setting.

[MikeH]

Unless you're trying to do something I'm totally lost on, all you need to do is add a DC jack to your pedal and you can use that adapter.  That adapter puts out DC voltage just like a battery.

[scabrabbit]

No that makes sense...I thought it was more complicated. When do I need to worry about voltage regulators? Only if I build my own adapter?

[MikeH]

Yes- what your average wall-wart type adapter does is convert high voltage AC into low voltage DC- this requires some transformation, regulation, filtering, etc- which all goes on inside the wall wart.  You may have seen some older effects that have a wall plug- these generally have a transformer/regulator inside the effect, instead of all that mumbo-jumbo being in an external wall wart.

[scabrabbit]

Thanks!