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Current Monitor Group (1606)

Current Monitor Group (1606). Maya Dubrow Barath Parthasarathy Andrew Pikul Jason Stock Advisor: Ali Gokirmak. Outline. Executive Summary System Breakdown Characterization and Data Future of this Project.

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Current Monitor Group (1606)

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  1. Current Monitor Group (1606) Maya Dubrow Barath Parthasarathy Andrew Pikul Jason Stock Advisor: Ali Gokirmak

  2. Outline • Executive Summary • System Breakdown • Characterization and Data • Future of this Project Executive Summary:We’ve designed a ranging HIGH-SIDE current monitor, which attaches directly to Phonon’s DC supply. We use a low-resistance sense resistor and amplifier to measure the sense voltage drop. We’ve characterized this circuit on a mix of breadboard and PCB. We’ve met the requirements we were given and have designed improvements to be made in the future. The company wants software too.

  3. System Breakdown • Built and Tested • Sensing Circuit • Ranging Circuit • Designed • Signal Postprocess • Anti Aliasing Filter • Second Stage Gain • Microcontroller (Controls All ICs) • Power Circuits

  4. Sensing Circuit • Amplifier: LTC6101 • Amplifies signal to be used for output. • 3 separate op amps are used to reduce error caused by FET impedance. Trimmer’s will be used to correct gain variability. • Very low thermal coefficients • High power rating

  5. Ranging Circuit • Optoisolators: P227G • Mosfet: BUK 72150 • Mux: MAX 7368 • Analog 2x 4:1 multiplexer • 100 kHz bandwidth • Supply voltage 3.3V

  6. Second Stage Gain • ADG704 • Analog 1x 4:1 multiplexer • Large bandwidth (MHz) • Supply voltage 3.3V • OPA1612 • Max supply voltage 36 V • Bandwidth of 40 MHz at G=1 • Low input offset voltage and current • Low common mode voltage of +/-2V

  7. Anti-Aliasing Filter • Anti-Aliasing is a common practice using an anti-aliasing filter to limit, or restrict the bandwidth to that of the Nyquist limit. • LTC1564 • Digitally controlled antialiasing filter • Adjustable cutoff frequency from 10kHz to 150kHz in steps of 10kHz • The sampling frequency for our DAQ is 48kHz, so our cutoff frequency should be roughly 24kHz. • Using this filter would be problematic because we would have to use either 20kHz or 30kHz, so there would be some insufficient sampling rates.

  8. TI’s Webench • Ended up designing a 5th-order bessel filter from scratch using TI’s Webench software.

  9. LTC1065 • After a bit of research, we ended up finding a 5th order Bessel filter IC. • This helps immensely, and cuts down on implementation time. • LTC1065 • Antialiasing filter with linear phase response • Operates from +/- 2.375V to +/-8.0V • Maximum cutoff frequency of 50kHz (controlled by an internal or external clock) • An input RC circuit can be used to attenuate incoming signals close to the filter clock frequency • Choosing a certain resistance value, will keep the Bessel passband response constant. • 100:1 clock-to-cutoff frequency ratio • The LTC1065 will benefit from having a digital potentiometer in place of the input resistance, Rin. • This will allow Phonon to generate different sample rates of the Bessel filter based on a table in the LTC’s datasheet

  10. LTC1065 Schematic

  11. Power Circuits • Sense amplifier is self powered! • 3.3 Volts for IC • 24 Volts for 2nd Stage Gain (Post Processing) • Gate Driver

  12. Voltage Regulation • LM2585 (24 V) • Necessary for 2nd Stage gain • LM26001 (3.3V) • MUX • Gate Driver for LM61001 • Anti-aliasing filter • Microcontroller

  13. Gate Driver • LTC1910 • Responsible for detecting a current overload within the LTC6101. • The devices turns off in harsh environments. • This time can be adjusted by the capacitance on pin 2 (150,000*C=T(delay)) • Example: .33uF resistor gives us 50ms termination

  14. 𝝻Controller • 4 GPIO for 3 multiplexers (range and gain) • 4 GPIO for serial to DAQ • 3 for possible auto ranging (comparator detection) • 3 for SPI to Filter • 1 for Clock to Filter • Total: 15 I/O… we can use a ATmega328P! (power up/power down behavior is very important)

  15. DAQ (USB → Computer) Software • Company Device • 8 analog in (or 4 differential) fs = (48 kHz / #channels) • 16 GPIO (Software Polled) • .NET Driver (VB Requested) • Can do a voltage sweep with the DC Supply • Collects Data and Displays • Exports to Excel

  16. Collected Data for 15 ohm DUT Blue- 0.1Ω Rsense Red- 0.25Ω Rsense Green- 0.5Ω Rsense Data was collected for 6 other DUTs: 49Ω, 100Ω, 200Ω, 500Ω, 1.2kΩ, 2.5kΩ.

  17. Analysis

  18. Analysis

  19. Analysis

  20. Analysis

  21. Conclusion: Areas of Success • Deliverables tasked to us by Phonon were achieved. • Relatively Low Budget • Sensing/ Ranging (<$150) • Power Supply, Anti-Aliasing, Second Stage Gain, Microcontroller (<$150) • Efficient code.

  22. Conclusion: Areas of Improvement • Lack of precise parts to complete finishing touches: • Power Circuit (Singular Power Supply) • Anti-aliasing (Limiting Frequency) • Microcontroller (IC Control) • Second-stage gain (Automatic Range Switching)

  23. Acknowledgements • Thank you to Phonon Corporation for access to parts. • Thank you Dr. Gokirmak for helpful discussions.

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