PDA & Project54 Michael Farrar on 16 Dec 2008 08:24 pm
Characterizing power consumption of handheld devices: the Symbol MC70 / MC50 EDA
With our Hampton, NH deployments just around the corner, we sought concrete evidence that the capacities of our handheld-device batteries, of Symbol MC70 / MC50 EDAs, would provide officers with Project54 (P54) services throughout the duration of their eight hour shifts. To do so, I’ve modified the existing structure of our automated button-presser, the P54-Testbot, now offering battery-usage logging of something I like to call “sequential routines”. Contrary to the normal operation of P54-Testbot, the sequenced operation allows for sets of button-presses to be categorized as sequences. Because of reduced display area, the handheld version of P54 has a significant number of button-locations declared as absolute screen-positions rather than P54-typical row-column declarations. To increase its ease-of-use, the sequential routine’s algorithms have been designed to support each method of button-creation. After the execution of a sequence the percentage of battery remaining is recorded and textually labeled with the sequence’s name. Sequences are then repeated at developer-defined frequencies. All parameters governing these sequential routines are editable through the device’s registry, pictured below, along with a termination value which causes P54 to exit if the main-battery level becomes less than some threshold.
Results from the sequences pictured above are depicted in the figure below. Slight differences in the definitions of the sequences’ iteration count per hour caused the variances between the origination points of the colored plots. I’ll spare you from most of the details, but not all. Each plot represents a test consisting of three sequences: one submitting a records query, another activating the barcode scanner, and a final capturing an image. The black plots represent tests of lower frequency sequences (about 22.5 minutes), while the red plots represent tests of higher frequency sequences (about 15 minutes). As we can see, even in the case of higher frequency sequences, the battery capacities of our handheld devices fall to 10% after a period of 10 hours, exceeding the 8 hour requirement.
Deployment results to come
Michael Farrar