Arduino as power source

Hi guys,

please, have a look at my circuit
My goal is to provide 24 V to pin X6A pin 2. For this, I am planning to use the 5v pin of my arduino mega 2560 and convert to 24 V with a step up converter MT3608.

The concern is that since my power source ( = my arduino ) is not a stabil power source, the X6A pin2 gets over voltage. Need some comments / feedbacks from you, guys.

Unbenannt.JPG

You have not provided enough information for a proper answer, other than to say you should power the MT3608 from whatever power supply you power the Arduino with, not the 5 v output of the Mega. The schematic is useless to provide the necessary information, specifically the required 24 volt current.

The maximum current you can draw from the Mega’s 5 volt pin depends solely upon how you power the Mega. Powered with 12 volts into the barrel jack, it might be good for about 100 ma on the 5 v output. That means the most you’ll have is 5 / 24 * 0.1 or about 20 ma available at 24 volts.

The concern is that since my power source ( = my arduino ) is not a stabil power source, the X6A pin2 gets over voltage.

No, the boost converter does not work on a fixed number of times boost, but on the actual output voltage. So once you set the output voltage that stays fixed ( within reason ) if the input voltage changes.

Arduino pin is good for 25mA continuous current. When you boost 5V 25mA to 24V you might get 4 or 5mA out.

What you should do is use the Arduino pin to switch a logic level MOSFET that lets external to Arduino board power flow to your device, the FET can channel 24V directly or as much 5V amperes as your booster needs to make useful mA at 24V.

Most boost converters will have starting current (to charge the input capacitor) that exceeds what an Arduino pin can supply without risking damage to the microcontroller. Many of them have a quiescent current (the current they draw with no output current, just to keep the converter and control circuitry running) that also exceeds that - and that’s before we consider the load. The current required at the input, in addition to the quiescent current, will be 4.5 to 5 times the output current for a boost of 4x voltage (an ideal converter would require 4x the current at input as output if boosting voltage by 4x; real converters will waste some power, though common efficiency ratings are often in the 80-90% range).

Arduino GPIO pins are not suitable for use as a power source except for the lightest of loads - as others have said, use it to control a fet.

Arduino pin is good for 25mA continuous current.

Correct for an i/o pin, not correct for the 5v output as both stated and shown by the OP.

OP’s image:

You can pull more off the 5V pin, sure. How is the Arduino board powered?

Note the 2Amp fuse left/top on the diagram.
How much is this 24volt board going to draw.
Definately a NO if more than 50mA.

Might have to get a 24volt supply to power the top board,
and a buck converter to power the Mega from that 24volt supply.
Leo..

Thank you for your answers!

  1. The arduino will be powered with a usb cable.

  2. It looks like that the top board have 2 A fuses. So, I would like to have same fuses between my arduino and the Pin3.
    What is your opinion? I would like to protect the top board from the arduino. So what ever I do with my arduino (providing with 50 V, maybe ?), top board should be protected.

The USB can only supply 500mA maximum. So when you boost the voltage up to 24 V, that is times five, the maximum current drops by five times, so the maximum current you can get out of it is 100mA. These are very rough calculations so it is likely to be 10 to 30mA less than this.

Putting a 2A fuse in this supply seems a bit futile.