Squeezing more juice out of a PSU w/o raising voltage

Started by no one ever, April 30, 2006, 11:48:55 PM

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no one ever

How do power supplies such as Voodoo Lab's Pedal Power raise the amperage of an output with little DIP switches? (hopefully) I'll be getting a Spyder-esque power supply unit soon, but it has 100mA outputs and one or two of my pedals need 120mA or 200mA.

:icon_question:
(chk chk chk)

cd

The Pedal Power 2+ only shifts the voltage, the max output current remains the same.

If you've read the Spyder article on GEO, adjusting voltage is trivial with a couple of carefully selected resistors and an adjustable voltage regulator like the LM317.

If you need more current, depending on how well matched the individual 100mA sections are, you could run a couple (or more) in parallel - though the best thing to do is get the right amount in the first place.

Of course if you've never wired up AC line voltage power before (or even if you have, and someone else who hasn't is reading this) BE CAREFUL! 

no one ever

Quote from: cd on April 30, 2006, 11:57:53 PM
The Pedal Power 2+ only shifts the voltage, the max output current remains the same.

If you've read the Spyder article on GEO, adjusting voltage is trivial with a couple of carefully selected resistors and an adjustable voltage regulator like the LM317.

If you need more current, depending on how well matched the individual 100mA sections are, you could run a couple (or more) in parallel - though the best thing to do is get the right amount in the first place.

Of course if you've never wired up AC line voltage power before (or even if you have, and someone else who hasn't is reading this) BE CAREFUL! 

I thought as much... thanks, cd.
(chk chk chk)

Processaurus

Is that one of the Huge PSU's by chance? 
I'd parallel two of the secondaries on the transformer and hook that up to one regulator, maybe heatsink that regulator for good measure if it isn't already.  I don't know if its good practice to parallel two regulators.

tommy.genes

I just got my Huge power supply this weekend. It is a transformer with two 115V primaries and ten 16V secondaries each feeding a DF04M bridge rectifier and then a uA7810C regulator wired for a fixed 10VDC output. Both the rectifier and regulator are rated at 1.5A.

You can find a uA7800 series datasheet at Alldatasheet.com. I need to do some more reading myself, but Figure 3 of the datasheet shows a small schem for an adjustable-output regulator using a uA78XX chip. Also, Figure 6 and the following accompanying text seem to address Processaurus' concern.

QuoteIn many cases, a regulator powers a load that is not connected to ground but, instead, is connected to a voltage
source of opposite polarity (e.g., operational amplifiers, level-shifting circuits, etc.). In these cases, a clamp
diode should be connected to the regulator output as shown in Figure 6. This protects the regulator from output
polarity reversals during startup and short-circuit operation.

I'll make sure I understand this all a little bit better before I start applying AC line voltage to a modified circuit.

-- T. G. --
"A man works hard all week to keep his pants off all weekend." - Captain Eugene Harold "Armor Abs" Krabs