I wonder if a laptop USB port is enough or I have to use an external power supply if the NodeMCU under heavy load. Here is my list of sensors and port used.

D1 to D7

Sensors: Turbidity sensor, Flow sensor, Temperature sensor, 4 led

  • 1
    That depends on how much current all that needs. We cannot know that. You didn't give us enough information. USB is limited to 500mA
    – chrisl
    Commented Nov 14, 2019 at 2:24

2 Answers 2


standard current you can draw from a usb port is 500 mili ampere with 5 volt(you may get even more but it is not recommended) . so if you want to calculate

sensors are very low current about 1~2 mA(but you must check out datasheet)

turbidity for example draws 30 mA

temperature ds1820 is 1 mA

flow is up 2 mA

the LEDs based on resistors series with them you normally up to 3 mA for each(1k series to 3.3 volt)

if you sum up all of them


but you should consider other consumers for example if you need 3.3 V you need a regulator such as ams1117 and it may waste some mili Ampere (not too much) and you certainly have a microprocessor and you should check data sheet but consider 100mA for that in worst case.

to count all of them the answer is YES


Sensors don't usually require that much current and a usb port should be able to handle 4 leds and the MCU without a problem. If you are using an Apple laptop it will disable the usb port temporarily if you draw too much current from it. Some PC laptops probably do the same.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.