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### Topic: Test how much power something is using (Read 1 time)previous topic - next topic

#### kculm

##### Feb 12, 2013, 03:15 am
I know this is a noob question but, how can I tell how much power something is really using.

I have a small project made up of a few LED's and an atTiny85 and I would like to know how much power it really consumes so I can figure out the best way to power it.

Thanks

#### larryd

#1
##### Feb 12, 2013, 03:45 amLast Edit: Feb 12, 2013, 03:47 am by LarryD Reason: 1
Quote
how much power something is really using.

You probably mean how much current.
Measure the total current the project is drawing with an ammeter/digital multimeter DMM

No technical PMs.
The last thing you did is where you should start looking.

#### MaJiG

#2
##### Feb 12, 2013, 03:49 am
Place a voltmeter to measure the exact voltage from board ground to board VCC, then place an ammeter between the power ground and board ground so that current goes thru the meter.

Power = Voltage x Amps

#3
Thanks guys.

#### dc42

#4
##### Feb 12, 2013, 06:31 pm
You can calculate the approximate current. Knowing the LED series resistors you have used and the LED forward voltage drop, calculate the current taken by the LEDs. Then add the power consumed by the ATtiny, which you can get from the graphs in the datasheet.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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