156A Week 10

Overview of Status of Analysis, Design, Fabrication, Tests, etc.

• • This week we successfully built and tested a breadboard circuit that properly mux/demuxed our three desired signals (ground, current in, voltage measured). We are still in the ongoing process of design for the current injection, power management, and data storage modules; however, we have made thorough progress in simulations for current injection, informing us of distinct trade-offs among all available current source options. Validation for risk reduction testing is ongoing throughout this process.

Accomplishments from Previous Week

• • Built prototype circuit to test operation of mutliplexer/demultiplexers (mux/demux).

    • Wired and tested switching current injection and grounding of 8 nodes using 2 demuxes and LEDs. 

• • • Sampled voltage of other 6 nodes in each configuration (using a single mux). Observed input vs. output and time response of muxes using oscilloscope.

• • • Wrote Arduino code for 8 node sampling configuration

• Performed analysis of a constant current source circuit using LTspice simulations

  • Simulated the LT3092 constant current source given various circuit load conditions

  • Simulated voltage source rather than an IC to understand the trade-offs in each configuration

  • Created GitHub repository for code organization/collaboration

Goals for Next Week (list names after each item). Use specific and measurable objectives.

• Order 32:1 mux/demux - Aaron

• Test LT3092 IC to validate simulations (current output) - Jacob

• Test LM334 IC as a possible alternative to LT3092 - Jacob

• Prepare risk reduction presentation for finals week - All

• Test L7805 voltage regulator with 9/7.4 Volt Li ion batteries for precision and noise - Matthew

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

• This weeks meeting (March 9th) with our sponsor, Kenneth Loh, brought us up to speed on the project requirements and he had a graduate student demo the sampling process for the resistive film. He was content with our plan to prototype the sample acquisition and current injection stages of the project (deemed higher risk).

Instructor Comments from Last Meeting and Actions Taken to Address these Comments  (indicate date of comments and if via email or in person)

• • On 3/1/2018, during our project definition presentation, Jerry commented that we need define/discuss design parameters (e.g. tolerance) regarding the constant current source with the project sponsor.

  • During our weekly meeting on March 2nd with our sponsor, Kenneth Loh, we decided on a tolerance of +/- 2% for the current source while sampling is being recorded.

Comments from Other Students in the Class (indicate date of comments and if via email or in person)

• • N/A

Risks and Areas of Concern

• The largest risk right now is still the current injection and measurement. We are concerned that the specific ICs available may not adequately regulate current (LT3092 has a minimum current regulation).

Resources or Information Required but not Available

• The resistances of the films that we need to measure.

Schedule

• • Thursday 3/15/18, 3:30p: Risk reduction meeting with Jerry (HSS 1330)

  • Friday      3/16/18, 5:00p: Sponsor meeting with Kenneth Loh (SME 413)

  • Next week (Finals week): Risk reduction presentations

Budget (list amount spent and amount remaining)

• • $46.26 Spent

  • $1353.74 Remaining

Progress on Report and Webpage

• • Updated webpage to most current state