[sdiy] speaking of power supplies...

[jhno]

i was curious about the viability of chaining voltage regulators together
in a power supply circuit. the idea is for the output of one regulator to
be tied to the ground of the next. the inputs can all be fed by one master
voltage, or each input can be tied to the output of the preceding
regulator, maintaining a constant differential.

e.g., to obtain +8, +16, +24 sources:


                 GND
                  |
                  |
>7808   >7808   >7808
| | |___| | |___|   |
| |       | |       |
| |       |_________|
| |         |
| |_________|
|
+24v


actually this diagram shows an insufficient supply, since each regulator
needs a couple volts above reference at least. however, before thinking
about this i breadboarded it, and it seemed to work okay (nothing melted,
only one output voltage was off reference). is the stress being distributed
among the devices?

the solina +/-15v supply could be:


                         GND
    *               #     |
                          |
>7808   >7808   >7808   >7808
| | |___| | |___| | |___|   |
| |       | |     | |       |
| |       | |     |_________|
| |       | |       |
| |       |_________|
| |         |
| |_________|
|
|
|
+V >= 34


then you would take the pin below '#' as ground, GND becomes the -15v
source, and '*' becomes +15v.

any comments regarding the problems, risks, fire hazards, dangerous fumes,
wolves in sheeps clothing, crimes against humanity, or just general
boneheadedness of such a scheme would be most welcome.

jhno


ps - on a related note, how come there are negative voltage regulators,
instead of just wiring positive regulators backward? hmmmmm....


this message has been brought to you by: a big pile of 7808 regulators. no
7815's. no 7908's...