Hello,
I am doing an end-of-study internship and I have a question on how to know the energy consumed by a raspberry card or other cards and the sensors that go with it?
Thank you in advance for your feedback.
You can know the energy consumed by a RPi by at least two methods:
+1drgeoff wrote:1. Measure it.
from BoyOh
But as drgeoff said, Ohm's law has nothing to do with power. You said "first check the voltage and current, then using Ohm's law to give wattage." If you know the voltage and the current then the power is simply P = VI, you cannot apply Ohm's law to calculate power from voltage and current, all Ohm's law will tell you is the resistance. From the rest of your post it looks like you were suggesting using resistance and voltage to calcule current (where Ohm's law is relevant) but that isn't what you said at the start where you stated that you use Ohm's law to calculate power once you know voltage and current.boyoh wrote: ↑Sun Feb 16, 2020 11:13 amfrom BoyOh
The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer
If you read the posters question you will see the Word ENERGY
Regards BoyOh
From BoyOhPaeryn wrote: ↑Sun Feb 16, 2020 3:10 pmBut as drgeoff said, Ohm's law has nothing to do with power. You said "first check the voltage and current, then using Ohm's law to give wattage." If you know the voltage and the current then the power is simply P = VI, you cannot apply Ohm's law to calculate power from voltage and current, all Ohm's law will tell you is the resistance. From the rest of your post it looks like you were suggesting using resistance and voltage to calcule current (where Ohm's law is relevant) but that isn't what you said at the start where you stated that you use Ohm's law to calculate power once you know voltage and current.boyoh wrote: ↑Sun Feb 16, 2020 11:13 amfrom BoyOh
The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer
If you read the posters question you will see the Word ENERGY
Regards BoyOh
From BoyOhdavidcoton wrote: ↑Sun Feb 16, 2020 5:37 pmSorry, Boyoh, but you are misremembering what is Ohm's Law and what is Watt's Law.
Ohm's Law concerns the relationship of voltage (V, in Volts), current (I, in Amps) and Resistance (R, in Ohms).
V=IR
Watt's Law concerns the relationship of power (P, in Watts), voltage (V, in Volts) and current (I, in Amps).
P=VI
You are right that we can derive secondary formulae to determine any one quantity from any other two. The written form you give is misleading because the "2" representing the square operator doesn't show as a superior (raised) character. They should look like this:
P=V²/R
P=I²R
Other notations are available, such as "*" for multiply and the one you used divide (I can find it in Unicode but not make it work here).
BoyOhPaeryn wrote: ↑Sun Feb 16, 2020 3:10 pmBut as drgeoff said, Ohm's law has nothing to do with power. You said "first check the voltage and current, then using Ohm's law to give wattage." If you know the voltage and the current then the power is simply P = VI, you cannot apply Ohm's law to calculate power from voltage and current, all Ohm's law will tell you is the resistance. From the rest of your post it looks like you were suggesting using resistance and voltage to calcule current (where Ohm's law is relevant) but that isn't what you said at the start where you stated that you use Ohm's law to calculate power once you know voltage and current.boyoh wrote: ↑Sun Feb 16, 2020 11:13 amfrom BoyOh
The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer
If you read the posters question you will see the Word ENERGY
Regards BoyOh
Ohm’s law can be used to find volts, watts, amps, or ohms if any two values are known. This can be done using the Ohm’s law and power formulas above. The Ohm’s law wheel shows all of the formulas that can be used to find volts, watts, amps, or ohms.boyoh wrote: ↑Mon Feb 17, 2020 8:40 pmBoyOhTHE-PIE-CHART-FOR-OHM’S-LAW[1].pngPaeryn wrote: ↑Sun Feb 16, 2020 3:10 pmBut as drgeoff said, Ohm's law has nothing to do with power. You said "first check the voltage and current, then using Ohm's law to give wattage." If you know the voltage and the current then the power is simply P = VI, you cannot apply Ohm's law to calculate power from voltage and current, all Ohm's law will tell you is the resistance. From the rest of your post it looks like you were suggesting using resistance and voltage to calcule current (where Ohm's law is relevant) but that isn't what you said at the start where you stated that you use Ohm's law to calculate power once you know voltage and current.boyoh wrote: ↑Sun Feb 16, 2020 11:13 am
from BoyOh
The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer
If you read the posters question you will see the Word ENERGY
Regards BoyOh
What Paeryn said.
BoyOhPaeryn wrote: ↑Sun Feb 16, 2020 3:10 pmBut as drgeoff said, Ohm's law has nothing to do with power. You said "first check the voltage and current, then using Ohm's law to give wattage." If you know the voltage and the current then the power is simply P = VI, you cannot apply Ohm's law to calculate power from voltage and current, all Ohm's law will tell you is the resistance. From the rest of your post it looks like you were suggesting using resistance and voltage to calcule current (where Ohm's law is relevant) but that isn't what you said at the start where you stated that you use Ohm's law to calculate power once you know voltage and current.boyoh wrote: ↑Sun Feb 16, 2020 11:13 amfrom BoyOh
The watt (symbol: W) is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer
If you read the posters question you will see the Word ENERGY
Regards BoyOh
BoyOh You said the last chart was wrong, I hope this one is correct ,and as no Printers Errordavidcoton wrote: ↑Mon Feb 17, 2020 11:46 pmWhat Paeryn said.
Plus, that graphic appears to have two incorrect formulae -- the ones involving square roots.
Should be:
P=√(PR)
I=√(P/R)
At least I think so. It's late