I am planning to create a water valve controller using an MCU and a set of solenoid-controlled valves. The solenoids run on 24VAC (40mA inrush, 20mA holding), and I have a 24VAC 300mA wall-wart I wish to use (standard sprinkler timer transformer).
The MCU is on a board that draws ~100mA, and it has an on-board regulator, so I can supply it either 5V directly (bypassing the regulator) or 6-12V through the on-board regulator.
My question is how best to use this transformer to also power the MCU. I can throw together a quick little power supply using a rectifier and an LM317, but I believe I'm approaching the limits of the LM317 here. Am I better off with another transformer to drop the 24V to something more reasonable first?
The MCU is on a board that draws ~100mA, and it has an on-board regulator, so I can supply it either 5V directly (bypassing the regulator) or 6-12V through the on-board regulator.
My question is how best to use this transformer to also power the MCU. I can throw together a quick little power supply using a rectifier and an LM317, but I believe I'm approaching the limits of the LM317 here. Am I better off with another transformer to drop the 24V to something more reasonable first?