I am building a circuit board that will have a lot of functionality with both Analog and Digital signals as well as operating (8) 5V relays.
I am going with two 780X series regulators 5v at 1.5AMP with heat sinks one for the main board and a second to power a Raspberry PI (using for display, internet, etc) and one 3.3 LD1117 800mA regulator for some needed 3.3v stuff on the main board. I would like to find a transformer small enough to fit on the main board and output around 9-15V but I am unclear on how to size them. The regulators will be able to handle 15V which might be better as far as transformer size is concerned.
Do I simply calculate VA for full load on the regulators figuring in efficiency and do a formula on that to size a transformer or is there another way I should be looking at this?
Thank you in advance for any help and guidance
I am going with two 780X series regulators 5v at 1.5AMP with heat sinks one for the main board and a second to power a Raspberry PI (using for display, internet, etc) and one 3.3 LD1117 800mA regulator for some needed 3.3v stuff on the main board. I would like to find a transformer small enough to fit on the main board and output around 9-15V but I am unclear on how to size them. The regulators will be able to handle 15V which might be better as far as transformer size is concerned.
Do I simply calculate VA for full load on the regulators figuring in efficiency and do a formula on that to size a transformer or is there another way I should be looking at this?
Thank you in advance for any help and guidance