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Topic: Confused with power supply on arduino  (Read 173 times) previous topic - next topic


Hi, I'm currently working on a project with RFID module RC 522 and other components like HC-SR04 (ultrasonic sensor), a buzzer and an led. RFID module RC 522 requires just 3.3v to work while the rest requires 5V to work. Since the arduino uno board has 5v and 3.3v option, can i just directly connect the RFID module to the 3.3v power supply given out by the arduino board and the rest of the components be connected to the common 5V power supply on a breadboard?

Thank you! :)


Can you tell the current requirement of the RFID module ??
Remember that the 3v3 on arduino can supply 50mA max.
Murphy always gets me ...


Apr 27, 2016, 07:33 am Last Edit: Apr 27, 2016, 07:34 am by JimboZA
You also need to be careful with the buzzer's current: assuming you want to switch it on and off, that would mean hooking it up to a digital pin. They can provide 40mA max, 20mA preferred, which is OK for an LED but make sure the buzzer doesn't need more. If it does, you would need to use the digital pin to switch a different supply for the buzzer, thusly, where the multiple LEDs in the schematic are your buzzer.

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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0


No you can not just power your RFID reader with a lower supply you also need to level shift the signals connected to the RFID board. Unlike I2C they don't have to be bidirectional level shifters, just a single direction. How hard this is depends on what else is on the SPI bus.


Remember that the 3v3 on arduino can supply 50mA max.
True for some Arduinos, but not all.
e.g. the Uno_Rev3 has an lp2985-33dbvr regulator that can deliver 150mA.

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