I have an the following components:
- Arduino Mega (9V)
- 8 relays (5V)
- 4 AC/DC voltage sensors (5V)
- SIM800L (4.1 V)
How many power supplies do I need on my circuit board?
Is it good idea to use one step-down module (8A) with voltage regulators?
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\$\begingroup\$ "step-down module" - Step down from what? What is the system power supply voltage? Also, what are the peak current requirements for each of the devices? \$\endgroup\$– AnalogKidCommented May 19, 2022 at 23:48
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\$\begingroup\$ @AnalogKid I have a 12 volt power supply, and I want to step down to 9 volt. peak current for relay is 70mA. for Mega 73mA \$\endgroup\$– vitoCommented May 20, 2022 at 0:07
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\$\begingroup\$ SIM800L should be 3.3V? \$\endgroup\$– Criticizing Israel not allowedCommented May 20, 2022 at 8:20
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\$\begingroup\$ @user253751 no. They require at least 3.8V. \$\endgroup\$– Rohat KılıçCommented May 20, 2022 at 8:46
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1 Answer
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The Arduino Mega board can accept power from its barrel jack or the USB connector. It auto-selects one or the other depending on which source is present. If the barrel jack is used, the on-board regulator makes 5V, which you could power directly with 12V. If you connect only USB, then 5V comes from USB. Either way, there's no need to make 9V.
Once the Mega is powered you could take some 5V power from it for the relays and the sensor. It has enough extra to do that (up to 800mA for the LD1117S50 if the barrel jack is used, 500mA ~ 1A if USB us used.)
That leaves the Sim800l. The module has a 2A peak current. Being so power hungry means this module should have its own 4.1V regulator derived from either your 12V or some other supply. Their datasheet shows references for an LDO with 5V or a DCDC for a higher voltage.
I suggest that the Sim800l have its own Li-ion battery run off 5V with a charge control: basically, a 'power bank' type circuit that could also run off Arduino 5V. The battery then handles the peak and 5V keeps it topped up during idle times.
answered May 20, 2022 at 1:32