user47270: I want to use a nodemcu to water my plants. I connected a pump with a 2N2222 transistor (I know i should add a diode and a pull down on the gate). The pump is DSL370 and when it is off i measure 4.4V on the Vin pin while using a 2A charger connected to the USB port. When the pump is active, the vin voltage drops to 4.1V and the LCD becomes hard to read. I measured the current the pump uses and it is 300mA. What is the reason for the voltage drop? I thought the charger should be able to handle it.


user33871: Your charger may be able to handle 300mA, but you're pulling that power through your Arduino and that isn't good.  The pump should have a separate power supply, or at least be powered in parallel with the Arduino.  Don't pull power for a motor from the Vin pin unless you just want to destroy the Arduino.  

47270: <p>I want to use a nodemcu to water my plants. I connected a pump with a 2N2222 transistor (I know i should add a diode and a pull down on the gate). The pump is DSL370 and when it is off i measure 4.4V on the Vin pin while using a 2A charger connected to the USB port. When the pump is active, the vin voltage drops to 4.1V and the LCD becomes hard to read. I measured the current the pump uses and it is 300mA. What is the reason for the voltage drop? I thought the charger should be able to handle it.</p>

<p><a href="https://i.stack.imgur.com/sT1uU.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sT1uU.jpg" alt="A schematic for my plant carrer"></a></p>
 33871: <p>Your charger may be able to handle 300mA, but you're pulling that power through your Arduino and that isn't good.  The pump should have a separate power supply, or at least be powered in parallel with the Arduino.  Don't pull power for a motor from the Vin pin unless you just want to destroy the Arduino.  </p>
