Hi, for the past week I've been trying to get an accurate measurement of the power consumption on the arduino, I've seen a couple of videos where people solder a resistor to the vcc pin on the mcu directly and measure over that using a oscilloscope, I can't do that right now since I don't have the needed equipment to solder the resistor, is it still possible to use the vcc gpio pin to attach a shunt resistor to?
Its not that a resistor is soldered to the VCC pin, the resistor is placed in series between the power supply and the power connection on the Arduino.
Thus all the current the Arduino uses flows through the resistor, so measuring the voltage drop across the resistor tells you the current.
A multimeter on current in place of the resistor will also measure the current flowing.
I assume you are talking about the UNO (same applies to others). Not all of the power goes to the microprocessor. You have losses in the regulators, LEDs etc. A resistor is one of the more accurate ways but there is also a voltage drop across the resistor. That voltage drop is directly related the current. Now you need to size the resistor so you can get a meaningful reading without dropping the voltage to much for the Arduino. A simple multi meter would do the job, and they can be very inexpensive. You will eventually need one anyway so get a decent one.
[u]How to measure current[/u] (with a multimeter).
It can be kind-of a pain (depending on your wiring/setup) because you have to "break" the circuit and insert the meter in series. And, you have to be careful because the meter is a short circuit and "bad things" can happen if you connect it in parallel with the power supply, etc. (Although, usually the fuse in the meter just blows.)
I measure resistance & voltage every day, but I very-rarely use a multimeter to measure current. (The power supplies on my workbench at work do have built-in voltage & current meters, so I do "keep an eye" on current every day.)
If you want power (Watts or milliwatts) it's calculated as Voltage x Current.
If you're powering via USB, try one of these: USB Power Meter (Color TFT LCD) - TOL-15571 - SparkFun Electronics
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