Measuring Arduino Power Consumption

Using Arduino Project Guidance
1

I am working on a project where I am trying to run an Arduino Uno a long time on battery; I am using the Lower Power library to put the system to sleep, waking on an external interrupt. I am not getting the battery life I would expect, so I am trying to read the power consumption with a multimeter. I connected the probes to the breadboard +/- strips and select mA. I am showing the Uno drawing about 3.5 mA when sleeping...and dropping to 3.3 mA when awake, which seems backward.

I have a couple of accessories attached (SD card, PIR sensor, VGA camera).

Am I measuring the current draw incorrectly?

Any guidance would be appreciated

2

CPARKTX:
Am I measuring the current draw incorrectly?

I'd say so.

Any guidance would be appreciated

Show us how you are measuring the current. A diagram would be best even if just drawn by hand.

FYI, here are measurements I've done:
http://forum.arduino.cc/index.php?topic=164146.msg1232507#msg1232507

3

I have a couple of accessories attached (SD card, PIR sensor, VGA camera)

On a UNO?

4

Yes, it is a Grove VGA camera; pretty slow, it takes about 15 seconds to write the data directly to an SD card. Not doing any image processing other than moving data from the camera to the SD card. See: http://www.seeedstudio.com/depot/Grove-Serial-Camera-Kit-p-1608.html

5

Thanks for the link.
It says:-

because 30W pixel wouldn't be overwhelming for Arduino, so that real-time image recognition is possible.

but it also says:-

Photo JPEG compression, high, medium and low grades

Now are they expecting to decode a jpeg image on an Arduino. I think that is not possible.

So as jack said:-

Show us how you are measuring the current.

6

I clearly don't understand how to correctly measure the current and am looking for help. Where should I be taking the measurement?

My setup was as follows: Uno powered through USB cable; power from Uno 5V/Ground pins running to breadboard, and PIR sensor, SD breakout board and camera breakout board all connected to breadboard power rails. I measured the current from the breadboard.

7

As was already mentioned you need to draw a diagram of all the connections and post a photo of it.

...R

8

If the Uno is powered by USB, almost certainly it is not the Uno's current that is being measured. The description is still insufficient, hence the request for a diagram. Schematic diagrams are the standard worldwide accepted method of communicating circuit design, so it's a good idea to get comfortable with them.

9

Where should I be taking the measurement?

For that setup you need to break into the 5V wire in your USB cable and bridge the gap with your meter on the current range. However you need to be careful because the wires inside are wrapped in a sheath.
If you don't fancy that them power your Arduino with a 5V regulated supply and measure the current in that.

Or you could get one of these:-
http://www.maplin.co.uk/p/maplin-usb-power-meter-n55ce

Although the lowest current it will measure is 20mA