[sdiy] power supply

[harry]

Hi Caleb....

You need to know how much current you need at 9V. You might use a
9V battery, then measure the current. If it is quite low (maybe under 20mA
or so) you could use a shunt regulator with a  series resistor and a 9V zener
diode.

If the current was higher, a linear (series) regulator such as the 7809 would do
well.

The choice is usually that the shunt regulator is very 'fast' acting but can
suffer from
high power loss (watts)... where the linear regulator is 'slower' but has higher
efficiency.

Think of the shunt regulator as being like a "spillway" type dam... It maintains
a
preset water level above the dam... but could spill thousands (millions?) of
gallons
of water in a heavy rain...  still... its really almost impossible for the water
level to
rise more than a few inches over the dam.

The linear regulator is more like a dam to keep a constant level at the low side

of the dam... by opening valves to allow the proper amount of water to flow.
It does not waste water... but it takes some time to see that the water level
has
dropped and compensate by opening the valve, and waiting for the water to start
flowing.  Here... if the valves are not big enough, you cannot deliver the power

required (and it burns up trying)

The spillway dam is a "right now" proposition by comparison.

Series regulator delivers only the power you need.  What you don't use stays in
reserve.

Shunt regulator consumes a constant power... you suck off what you need and it
dumps the rest (via zener diode to ground).  This might sound like a bad
thing... but
lets say you were flashing an LED...  The shunt regulator might be passing 15mA
... with the LED on thats 10mA in the LED and 5mA in the Zener... and with the
LED off thats 15mA in the zener and 0mA in the LED... so the drain on the power
supply is constant and the LED switching will not cause clicks in other audio on
the
supply.

The series regulator will turn on and off... 10mA with the LED on.... 0mA with
the
LED off. This change of current might 'rock' the power supply and make noises in
other audio circuits sharing the supply...

So think ...
Low power only = shunt regulator
Higher power = linear series regulator
Very High Power = switching regulator  (usually avoided in synth-diy circles).

Measure the current draw of your guitar module. You really need to know this...

H^) harry

Caleb Johnston wrote:

> This should be an easy question to answer for the experts.  I want to do
> this correctly so I dont fry anything.
>
> I have a module that runs on 1 9V battery.  I want to run this module from a
> power supply.  The power supply is Paia's 9770u which is the 'unregulated
> +/- 18 V DC @ 350 mA.  The connections on this power supply are +V,G,SG,-V.
> The module only has + and - for the battery.
>
> What would be the best way to do this?  Do I need to then regulate the
> power?
>
> thanks in advance for the help,
> Caleb
>
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