PowerScope

[mechg 17]

43oh Store link

 

I found myself wanting a dedicated power monitor to use while developing battery-powered application circuits, so I built one using the MSP430G2402. 

 

http://code.google.com/p/powerscope/

 

This device has already helped me identify and eliminate about 40% of the power usage of a project in-progress.

 

Right now, I just have the code as a zip file on the download tab, but if anyone wants to develop additional features, I can check the code into Subversion and create some branches. 

 

The board can be ordered for about $12 (for 3 boards) by uploading the Eagle .brd file to http://www.oshpark.com I don't make any money from oshpark.

 

Greg Glenn

http://gravitastech.weebly.com/

Edited April 9, 2013 by bluehash
Added store link.

[chytech 0]

Good, :thumbup:

[xpg 127]

That looks really good. I have found myself needing such a device quite a few times.

 

 

[mechg 17]

Once you use one, you will wonder how you got along without it.

 

When I first used it to monitor another MSP430 chip in LPM4,  the chip under test drew between 60 and 100uA, and that varied when I put my hand near it ! :-o  

 

I had just quickly thrown together some test code, and it turned out that I had left most of the I/O pins undefined, which causes relatively high power consumption even in low power mode, as well as capacitive sensitivity.  

 

Once I defined them all as output and set them low, the current draw went to the spec value of .1uA.

[Lord anubis 1]

 

Once I defined them all as output and set them low, the current draw went to the spec value of .1uA.

 

I believe you, but is this documented somewhere? Somebody knows?

[GG430 53]

There is a section in the User's Guide for unused pins.

E.g. 2xx page 44: http://www.ti.com/lit/ug/slau144i/slau144i.pdf

 

[mechg 17]

If all I/O pins are unused and unconnected, the following would insure no pins cause unwanted power draw in LPM on a MSP430G2402.

 

P1DIR = 0xFF;                    // All P1 pins set to output

P1OUT = 0x00;                   // All P1 pins low

P2SEL = 0x00;                    // P2 pins gen-purpose I/O

P2DIR = 0xFF;                    // P2 pins all output, unused

P2OUT = 0x00;                   // P2 pins all low

[username 198]

You must mean from dorkbotpcb XD . Neat project! Thanks for the share.

[mechg 17]

You must mean from dorkbotpcb XD . Neat project! Thanks for the share.

 

Oh, yeah... I had the link to OSHPark wrong.  It's fixed now.  It was formerly known as dorkbotpcb.

[tingo 22]

Useful project! :thumbup:

[chicken 630]

Great stuff! I started prototyping something similar as low-power is what fascinates me most about the MSP430. Will definitely use your schematic and code as a starting point to build my own.

 

Thanks for sharing! :thumbup:

[jpnorair 340]

How are you monitoring low currents?  Usually this requires an isolated amplifier or similar setup, in order to be accurate at low currents.

[chibiace 46]

very nice. alittle expensive to build though. why not combine something like this and those breadboard power supplies that sit at the end of the board. 

[mechg 17]

How are you monitoring low currents?  Usually this requires an isolated amplifier or similar setup, in order to be accurate at low currents.

 

The instrumentation amp is pretty good at measuring small voltage differences across a shunt resistor.   Here's another device that does something similar, although it outputs to a separate voltmeter:

 

      http://www.adafruit.com/products/882

 

The Analog Front-End chip would suffice without the instrumentation amp, but it has fairly low maximum voltage input ratings, so for this application I thought it best to add the instrumentation amp to protect the AFE.  

[mechg 17]

very nice. alittle expensive to build though. why not combine something like this and those breadboard power supplies that sit at the end of the board. 

 

I had considered that, but I like to keep things modular.  

 

Maybe we can lower the cost a bit if I can convince 43oH to sell the PCBs individually.