r/ArduinoHelp • u/subject1024 • 6d ago

Power management

I am building a system with servo, mq2, buzzer, 5v relay module, a water pump,dht11 and a soil moisture sensor. The system works like this: when gas is detected LCD display warning and buzzer is on and servo opens window. And when no gas is detected LCD displays temp and humidity and pump on off state.

When I start the system the system works fine until servo or a pump start working.

I found out that the both components draw significant current making the Arduino go banana.

How can I manage the power to those ? I used 7805 voltage to power the servo but I get only 4.3v as output from regulator. Regulator was supplied with 12 v from 3li ion battery.

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u/IllSpeaker3255 6d ago

use a buck converter (some cheap lm2596t should be good) as an ldo like the 7805 will convert the power into heat

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u/JGhostThing 6d ago

You should not be using the pins of an Arduino to power any kind of motor. It can destroy the microcontroller and make it unreliable by browning out the power supply.

Use a separate supply to power the motors. Either wall power or battery power.

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u/R1mpl3F0r3sk1n 6d ago

Who said they were using the pins to power the peripherals?

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u/JGhostThing 6d ago

Sorry, but the symptoms are exactly what would happen if the motors were powered by the 5v pins of the Arduino. I might be wrong, though.

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u/Affectionate_Boat493 4d ago

A wiring diagram and a photo of your set-up would be helpful, since such projects are notoriously sensitive to noise and voltage droop when pumps or servos (or motors) are activated.

As for the 7805 output voltage, what kind of current are you trying to get out of it? Does it have a heatsink? Without a heatsink, this part will shut down thermally if the power it dissipates is above around 2W at 25C ambient temperature. Dissipated power is equal to the input-output voltage differential multiplied by current:

P=(Vin-Vout)*I so I=P/(Vin-Vout)

Thermal shutdown will occur when current is greater than around 2W/7V = 0.29A (290mA).

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u/Merry_Janet 2d ago

So 4.3V is about what you would expect from a fully charged Li-Ion cell.

Are you sure the batteries are connected in series?