Overview of Status of Analysis, Design, Fabrication, Tests, etc.
This past week we received power management circuitry and the 9V voltage regulators. Testing proved that the voltage output of the 3.7V LiPo from our power management circuitry (PowerBoost 1000C) was within the least significant bit of our Agilent 34401A DMM. The 9V voltage was similar with no observable fluctuation with current sources, current sensing, and other components used. The team calculated and observed that to accomplish the necessary switching of the current sources and current mirrors, a 12V buck converter is needed rather than a 9V. This comes from an added current mirror used in the switching to hit the desired dynamic range (different method of switching than when the 9V VRs were first ordered). The team verified this with the appropriate wiring and a 12V lab source. The 32:1 muxes have been soldered to their appropriate DIP adapters; however, 3 of the pins on one mux do not properly switch. This comes from a soldering issue as the remainder of the switches function properly. The team has decided to do testing on a 29 node range rather than 32, while the hardware issue is fixed.
Accomplishments from Previous Week
Soldered multiplexers to SMT/DIP interfaces and connected to current source, current sense, and battery management circuitry.
Validated switching of 32:1 multiplexers using Arduino
Met and discussed ADC software implementation with James Strawson
Finalized first pass schematic with current source, current sensing, power interface and beaglebone interfacing
Selected external connection to sensing skins (D-Sub 37)
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Continue to develop codebase for project
Enable ADC device driver on BBB (Max)
Create and implement device tree overlay and pinmux groups for ADC interfacing (Max)
Begin writing C interface to the ADC driver and test it (Jacob)
Continue development of mux switching programs (Aaron)
Verify the dynamic range of current source with 12 volt rail (Matthew)
Finish first pass routing of PCB and complete DRC and other checks necessary for fab (Jacob)
Kick off fab to pcbfabexpress (Sunnyvale, CA) and get DFM feedback (Jacob)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
(4/12/18) - Ken did not give any action item feedback although he did say he was very satisfied with our progress and our results thus far.
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
(4/12/18) - Jerry mentioned the accuracy requirements of our product during our group presentation last week and what our ultimate goal was in terms of deliverable to Ken. As mentioned, the current requirement is set at 2% accuracy during switching, with the precision of measurements of the ADC at a 16-bit range (with appropriate voltages scaled to FSR of the 16 bits). The accuracy of the voltage measurements dictated by the internal voltage reference is accepted at a 0.02% deviation.
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
(4/12/18) - There was a comment on our decision to pursue an enclosure secondarily. We are simultaneously exploring an enclosure while our PCB changes form and is routed. As we mentioned, Ken ultimately expressed interest in focusing on the electrical side of the device, and form around that.
Risks and Areas of Concern
Complexity and depth of programming in C
Settling time of components during fast switching and signal integrity (need PCB to assess fully).
PCB layout of ADC and sensitive signals.
Resources or Information Required but not Available
12 Volt step up regulator ordered (comes on thursday 4/19)
Schedule
Wednesday 4/18/18: Progress meeting with Jerry and Pedro
Friday 4/20/18: Sponsor meeting with Ken
Budget (list amount spent and amount remaining)
$13.14 spent on 12V VR
$1067.35 Remaining (not including shop expenses)
Progress on Report and Webpage
First rough draft of the report has been uploaded to the website with select sections from Chapter 1
Webpage is continually being updated with new information (added to references for stuff in flight)