[sdiy] power supply pain

[Paul Perry]

At 01:15 AM 25/05/01 -0400, you wrote:

>but its too much voltage for the ADSR.  The power supply uses a 7812 to get
>the +12V, then taps off a resistor network to get the +9, and goes through a
>resistor network and a 7805 to get the +5. 
.there is the problem, the resistor divider cant supply enough current.
Use another 9v regulator to drop from 12 to 9, and another 5 volt reg too drop 
from the 9 to the 12.

Alternatively, you can run the raw supply driving the 12v reg directly to the 
9 and the 5 regs.
Which approach is best depends on what kind of currents are going to be drawn
by the various voltages. For simplicity, I would run them separately off the 
raw supply.

You dont see the problem with the voltage divider, because it takes so little 
current that there is no sag.

WARNING: negative regulators have a different pinout!!!

paul perry melb australia