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Topic: Arduino Mega the resistance between 5V and Gnd pins (Read 1 time) previous topic - next topic

Lapras

I am using Arduino Mega board in my project. I solder Arduino to perfboard with headers. At first, I measure resistance between 5V and Gnd pins in mega ohms. After soldering some transistors and IC sockets on perfboard, today I realized that the resistance between 5V pin and Gnd pin is approximately 1.6 kohm. I always measure without powering the board.

In my project I use 15 other ICs and transistors. Their Vcc and Gnd pin will be also connected to the 5V and Gnd pins of Arduino. Therefore, it is critical for me to be sure about whether there is a problem or not because also these ICs can be damaged also.

5V / 1.6kohm = 3.125 mA

Is this resistance is an expected value? Or is the current flows through power pins cause a damage to the board?

larryd

It is very difficult to hypothesize what the load is.

3ma would be a reasonable current draw.
However, you have a non resistance load since there are solid state components bringing powered.

The only way to see what the actual current will be is to power things up.  :smiley-twist:

Hopefully, things are wired correctly.




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Grumpy_Mike

Quote
today I realized that the resistance between 5V pin and Gnd pin is approximately 1.6 kohm.
The measurement of resistance between power and ground is meaningless unless you see zero which means you have wired up,a dead short across the supply. Any reading like the one you got simply does not convey anything. It is not an indication of future current draw in any way, it is just the result of the voltage used in the meter and the protection diodes inside any chips you have.

TomGeorge

#3
May 26, 2018, 02:09 pm Last Edit: May 26, 2018, 02:14 pm by TomGeorge
I am using Arduino Mega board in my project. I solder Arduino to perfboard with headers. At first, I measure resistance between 5V and Gnd pins in mega ohms. After soldering some transistors and IC sockets on perfboard, today I realized that the resistance between 5V pin and Gnd pin is approximately 1.6 kohm. I always measure without powering the board.

In my project I use 15 other ICs and transistors. Their Vcc and Gnd pin will be also connected to the 5V and Gnd pins of Arduino. Therefore, it is critical for me to be sure about whether there is a problem or not because also these ICs can be damaged also.

5V / 1.6kohm = 3.125 mA

Is this resistance is an expected value? Or is the current flows through power pins cause a damage to the board?
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

The reason that the resistance between 5V and gnd is going down is because of the ICs and other components that you are wiring into the circuit.
When you measure resistance, your DMM places a voltage across its probes and it measures the current that flows, this is converted to resistance, using OHMs Law.
As you add components to your circuit, you add more components for this current to flow.
Every time you add a component between 5V and gnd, you are adding another component in PARALLEL with the supply, so the resistance drops.

It is good practice to measure resistance from 5V to gnd, if you are building a circuit, it means you can check for shorts.

As you learn electronics you will learn to accept these sorts of readings, when you look at your circuit and consider the components you are adding

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Can you please tell us your electronics, programming, Arduino, hardware experience?
Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

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