Battery Duration using a typical 9v alkaline of 550 mAh capacity:
WickedNode can be configured to transmit every 10 sec, 10 min, 1 hr, or on an external trigger. The packets are just a couple of seconds long. As supplied, the WickedNode draws about 300 uA when asleep, which should deplete a 9v in about 76 days. Assuming 15 mA for 3 sec when transmitting, the battery could supply 44000 packets. The projected life for a combination of sleep and transmit is:
Mode Batt Life sleep / xmit
10 sec = 5 days 6.2% / 93.8% << used for testing
1 min = 22 days 28.6% / 71.4% << not available as shipped, for comparison only
10 min = 61 days 80.0% / 20.0%
1 hr = 73 days 96.0% / 4.0%
DCDW is assumed to be jumpered for "swarm of motes" configuration, the one most similar to WickedNode. DCDW transmit interval is set by a resistor/capacitor which can be any value, the 555 timer chip data sheet claims "from microseconds to hours" but in practice times longer than 10 minutes require special components. DCDW draws 100 uA when sleeping, for 229 days of duration. Transmit current is slightly lower at 12 mA, and the packet duration is set by another RC. Assume 5 seconds, (which allows a greater precision of measurement) the current is slightly lower current but nearly twice as long, the maximum number of packets is only 33000. In a combination of sleep and transmit the predicted battery life is:
Mode Batt Life sleep / xmit
10 sec = 4 days 1.6% / 98.4%
1 min = 21 days 9.1% / 90.9% << rate can be anything
10 min = 115 days 50.0% / 50.0%
1 hr = 196 days 85.7% / 14.3% << difficult to achieve
Other factors:
DCDW has nearly 12 bits of resolution, it could probably achieve 8 bit resolution with a packet of 3 sec or less (resistor), which would extend its life to 33 days at 1 minute interval or 143 days at 10 minute interval. WickedNode could be configured in firmware to provide a 1 minute interval. WickedNode provides a 60 minute interval, but there is little advantage in using it, since by that time sleep current dominates battery life and changing from 10 min to 60 min only extends battery life by 20%. In fact DCDW at 10 minute interval (its practical limit) lasts nearly 60% longer than WickedNode at 60 minutes.
WickedNode uses a different voltage regulator, at AltairLabs we modified a WickedNode to use the MCP1702 regulator that DCDW uses, and Wicked node quiescent current dropped 33% to 200 uA. This simple mod should boost WickedNode battery life to 83 days @ 10 min and 108 days @ 60 min. Still not as long as DCDW, but every bit helps.
DCDW clearly has the advantage for projected battery life. Lab tests are ongoing.
AltairLabs may brag now but WickedNode has many advantages which will emerge in upcoming rounds of this smackdown, or shootout, or whatever. We invite Wicked folks to comment, dissent, add to, or just generally acknowledge our awesomeness, as they secretly heft their brickbats for round 2.