Using Ground coming from Input_Pull Up pin

Hello All,

I am new with Arduino and have recently started to learn. So if this question is going to sound stupid then you know the reason :smiley:

Here is my question. When we use Input pull up which is inbuilt in Arduino it keeps the input pins as 'HIGH' by default instead of floating and we can make it 'LOW' running a code. Since LOW = Ground And also Arduino can share the Ground with any other higher power source without any issue, Can i use that Ground coming out from input pin to power a device where device's positive supply is coming from a different power source say 24 v Dc.

The idea is that i will first share the ground of arduino with the ground of 24v Dc external power supply for the common reference. Then i will take the positive coming from 24v dc external power source and negative from Arduino's input pin to power up my device. With this arrangement when i program to make the input pin go high and low every 2 seconds my device would turn on and off every 2 seconds. Is it possible ? If yes, then can this arrangment harm arduino in anyway as i am not using any resistor, transistor etc.

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Sorry for the confusion, yes it does keeps it 'high' but the idea is that we can switch between 'low' and high thereby controlling the device. Other then that do you think rest of the thing is good to go ?

It seems like it would be peculiar to be moving the GND instead of VCC/Vin. It also sounds like if the external device runs on 24V but you are moving GND with the Arduino then it would only move a maximum of 5V, which would give the external device a voltage a range of 19-24V. Perhaps you should use a relay or logic level shifter to provide 0-24V to the external device to follow a 0-5V output from the Arduino.

Could you explain more about what you are trying to control with the Arduino?

You can use the pin as an OUTPUT to control your device and write the output HIGH or LOW. But not directly.

Do not connect your 24V device directly to any pins of the Arduino (it will blow up the Arduino) with exception of GND. Use a relay board or transistor / fet to control the device.

The idea is that I will first share the ground of arduino with the ground of 24v Dc external power supply for the common reference. Then i will take the positive coming from 24v dc external power source and negative from Arduino's input pin to power up my device. With this arrangement when i program to make the input pin go high and low every 2 seconds my device would turn on and off every 2 seconds. Is it possible ? If yes, then can this arrangement harm arduino in anyway as i am not using any resistor, transistor etc.

Assuming I have understood you correctly; the short answer is that if you do this your Arduino will disappear in a cloud of nasty smelling smoke (or it might just die quietly).

The pins, whether input or output, must never be connected to a voltage lower then about -0.5V or higher than about 0.5V above the supply voltage (3.3V or 5V, depending on the model). Go outside those limits and you will probably cause damage. By connecting 24V to something and connecting that something to the Arduino you are connecting 24V to the Arduino, it won't last long.

Have a look at this:

Have a look at the Introductory Tutorials section.
There are some posts that will help your understanding of voltages, 0V and ground.