I have a device which works with 7V. I have a 7812 and 7805 already running in the circuit. Can I use the outputs of this voltage regulators to feed the 7V device?
I know this is possible in theory. But most practical voltage sources can supply current in only one direction. In other words, the device will drain arbitrary amounts of current (\$I_D\$) from the 12V grid, and give it back to the 5V grid. What will happen if the other circuit elements which are connected to the 5V grid drain current less than \$I_D\$? Will it cause the voltage on the 5V grid to rise up and the voltage on the device drop down?
Is this configuration OK in practice?