Tuesday, January 24, 2012

Propeller Beacon Power Consumption

I decided to take a look at power consumption during RF generation on the Propeller device.  I have a power monitoring device that logs current usage over time.  What I wanted to see was the power consumption that was attributable to RF generation.

The test setup is a Gadget Gangster board powered by my power monitor at 4.55 volts.  This is a somewhat low voltage, but is the highest voltage that it will generate.  This of course may affect my testing results, but the data is interesting nevertheless.

Since I am measuring current usage on a running processor, it is fun to look at the effect of code changes on power usage, but that is a side topic for another time.

Baseline, I wanted to see what current consumption is when the processor(s) are waiting in a delay loop with RF generation off.  This appears to be on the order of 20.8 mA while continuous RF generation on a single frequency appears to consume about 23.6 mA.  The script who's power consumption is graphed below loops turning the RF on and off every 5 seconds.

Now, I replace the script with a CW beacon sending at about 15 WPM my call sign and locator (KO7M CN87).  The power consumption graph looks very much like a QRSS Argo display.

As you can see, my call sign is clearly visible.  This script baselines at about 22.5 mA with RF off and 25.2 mA with RF on or about 3-4 mA attributable to RF generation.

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