Best way to supply 5v and 3.3v to a project

Other Hardware General Electronics
1

Hi,

I am building my own Arduino and need to supply 5v and 3.3v to the project which will be plugged into a 9v DC adaptor. I am unsure what the best way to do this is and wonder if there is anything wrong with my current method.

Schematic

Thanks in advance for your help.

5v-3.3v supply.png
5v-3.3v supply.png1300×570 19.9 KB

2

Your method is simple and OK. You just have to add a 0,33uF and a 0,1uF to the L7805CV according to the datasheet.

3

How much current does your project use at each voltage?

4

The 3.3v line will only be powering an ESP8266 which pulls 300mA when turned on.
The 5v line will pull

Relay 80mA
OLED 40mA

  • the ATmega chip.

The whole thing runs at around 150mA when initialised

5

a5m0d1:
The 5v line will pull

Relay 80mA
OLED 40mA

  • the ATmega chip.

Plus all of the current from the 3.3V

6

6d25ccec183af326b0489681e2deb000036ce7a1.png
6d25ccec183af326b0489681e2deb000036ce7a1.png1300×570 19.9 KB

Cascading regulators seems a silly idea in general. If the load of the lower voltage regulator is light and it is rated for the same input voltage, then just supply it directly from the input.

If its drop-out voltage permits it to reliably be supplied from the higher regulator output voltage, and it is drawing significant current then slaving it to the higher regulator may reduce the heat load of the lower voltage regulator, but clearly at the expense of the higher regulator which may well be working with a much higher drop and supplying whatever else it needs to.

Since the ESP8266 only draws full current intermittently, the LM1117 should be able to supply it when fed directly from the primary supply voltage.

7

Thank you for your replies,

I have set up both regulators in parallel and the do feel like they are giving off less heat.
I will buy a heat sensor and see what the difference is.

Again thanks for the help.