Confusion in power supply circuit

studiot

Joined Nov 9, 2007
4,998
Considering the size of the reservoir capacitor and the fact that the regulator IC is labelled simply 7805, I would expect it to be able to source up to 1 amp.

Note I say 'up to' because the regulator sets the voltage, not the current.
The current is set or drawn by the load. A heavier load with lower resistance will draw more current from a 5 volt supply.

With the 12 volt AC supply from the transformer the regulator will be dissipating around 15 watts at 1 amp so will need to be on a substantial heatsink.
 

GopherT

Joined Nov 23, 2012
8,009
A 6 or 9 volt transformer will lower the power dissipation of the voltage regulator.

the weakest link in thus supply will be either
- an overheating regulator (it will shutdown automatically if overheated)
Or
- transformer current (VA rating) is too small. ( make sure your output is at least 1.5 or 2 Amps (18-24 VA or more for 12 volt)
 
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