Hi! I thought of using a power supply by deconstructing a Switched mode power supply adapter for a project I'm doing without using a transformer power supply. Is it possible to do this? How do I calculate the current required by the system? My project consist of a PIC, 4 relays, DS1307 IC, LCD, PIR sensor and a TC35 GSM modem. Is 12V 1A power supply going to be sufficient for this?
You can find out from the datasheets the maximum current drain for PIC, DS1307 IC, and a TC35 GSM modem
These don't need much current LCD, PIR sensor
Big unknown are the relays, and how many will turn on at the same time. Often relays/motors/solenoids have a high inrush current. You might want a separate power supply for them, or isolate the power supply.