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Portable Lab Station

Portable Lab Station. Electronic Testing Equipment. Project Description. Power Supply – Low cost, low noise, portable source for providing DC voltages from a USB port. Signal Generator – Low cost, portable system capable of generating arbitrary waveforms.

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Portable Lab Station

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  1. Portable Lab Station Electronic Testing Equipment

  2. Project Description • Power Supply – Low cost, low noise, portable source for providing DC voltages from a USB port. • Signal Generator – Low cost, portable system capable of generating arbitrary waveforms. • Transistor Analyzer – Low cost add-on capable of troubleshooting electronic components.

  3. Power Supply Sean Lin AlhousseynouDiallo

  4. Specifications Technical Design Requirements • Low cost • Versatile: use on various low power applications • Input Voltages: 5 volts • Input Current: 500mA(USB) • Output Voltages: 1.0 – 20 volts • Output Current: 5mA - 345mA • Operating Frequency: 400Hz(Buck), 40KHz(Boost)

  5. Power Supply Technologies Linear Mode Power Supply PWM-Switching Power Supply • Operation: transistor(s) operate in linear mode. • Trade off: Larger Size (dissipating heat), Inefficient • Inefficient: regulates output by dissipating or burning off “unwanted” voltage as heat. • Operation: transistor(s) operate as an on/off switch mode. • Trade off: Complicate, Can be noisy (transient Currents), Efficient • Efficient: maintains the output voltage by on/off state operation

  6. Design Criteria Constraints associated with Power Supply Design • Design to specified or available input voltages and currents (AC or DC) • Determine power application: low/high power • Components sizes, weights, specifications

  7. Design Options DC/DC Switching Power Supply Design AC/DC Switching Power Supply Design (1-20V)

  8. Design Details • Buck-Boost converter • Switch opened, IL decreases • Switch is closed, IL increases • Vin <Vout Boost Mode • Vin >Vout Buck Mode • Output voltage is controlled by the duty-cycle.

  9. Test Results Overall Power Supply Performance • PWM waveform • Output Voltage ripple • Pmax: 6.9Watts

  10. Power Supply Conclusions Future Work • The buck-boost regulator can be used to generate a low to high voltage from a positive low input voltage. It is very efficient, and very cheap. • Using smaller surface mount components for more compact design.

  11. Signal Generator Andrew Averhart

  12. Specifications Technical Design Requirements • Variable Output Waveforms – Any arbitrary waveform • Frequency Adjustment – 1 Hz – 500KHz • Amplitude Adjustment • Measurement Error < 2% • Stable • Low Cost

  13. Design Criteria Waveform Generation Sampling Rate • 8 Bit Resolution • 28 = 256 Samples • 256 Point Lookup Table • Sample Rate = Output Frequency x Samples • 1 Hz to 500 KHz requires 256 sps to 128 Msps

  14. Design Options Initial Design Final Design Signal Extraction Stage Binary Counter SignalConditioning Stage Switch EPROM DAC Timer (555) Frequency Control Stage Op Amp (LM324)

  15. Design Constraints Constraints associated with Signal Generator Design • Variable output voltage must range from 5 Vpp to 30 Vpp. • The power supply unit must be able to supply voltage rails of -15 V and +15 V to prevent signal clipping. • Output frequencies for arbitrary waveforms are limited by both the input frequency and total number of samples.

  16. Design Details Signal Generator Dual Polarity Power Supply • The maximum frequency of the Timer (555) is 500 KHz • The maximum output frequency of the generator is; • Thus, the maximum output waveform is approximately 2 KHz • The output square wave from the Timer can be used as an output for high frequency applications (<500KHz) • 24V/400mA transformer drives the signal generator • 4 separate regulators must be used to supply all the adequate voltages; • +5V (Powers IC chips) • +10V (Powers DAC) • +15V (Positive Supply Rail) • -15V (Negative Supply Rail)

  17. Test Results Conclusions Future Work • Arbitrary Waveform generators are much more complex in design than Function Generators • Frequency range is critical in determining a Signal Generator’s performance capabilities • Add dual channel output support • Allow amplitude and frequency modulation capabilities • Digital LED Display support • Computer interfacing

  18. Signal Generator Prototype Package Includes Signal Generator with single channel output, Willem EPROM Programmer and additional EPROM memory. The model shown above contains original test circuit, breadboard mounted. The final prototype will contain PCB mounting.

  19. Transistor Analyzer Brad Hodges

  20. Specifications Technical Design Requirements • Vin = 5V • Input waveform – Sawtooth • Max current = 0.05 A • Current range – 50mA to 50uA • Low power consumption

  21. Design Criteria Constraints associated with Transistor Analyzer Design • Each resistor must match two requirements • The capability of the switch to handle the resistance • The amount of current desired • The transistor must be capable of handling any and all currentsflowing through it

  22. Design Options • Initial Design • Final Design

  23. Design Details • The PIC is programmed with a sawtooth waveform and directly controls the CMOS switch • The digital potentiometer sends the sawtooth waveform and 5V to the collector of the transistor • The resistors are used to regulate the current • R1-R4 are used to limit the base current • R5-R8 are used to allow for a large amount of collector current • A transistor-current buffer with an op-amp is used to provide more current to the collector of the transistor • The PIC sends back the output data to the PC, where it is read in and outputs a curve

  24. Test Results Overall Transistor Analyzer Performance • The PIC code both selects different resistors to use and generates a sawtooth waveform, which is outputted through the digital potentiometer • The resistor values are determined based on the desired current • The collector current is high, so the resistor values largely increase • The base current is low, so the resistor values are low and gradually decrease • The PIC establishes communication to the PC to send data values to be plotted into multiple output curves • The number of possible outputs is limited by the switch in use • 2^4 = 16 outputs

  25. Transistor Analyzer Conclusions Future Work • The programming must precisely match the wiring in order for the circuit to function properly • The resistors must not be too small or large for the switches to handle • The different base currents should be small, while the collector current should be large • Use more CMOS switches in the circuit to allow for a wider output range • Use a serial communication to directly read in the data values on the PC and output the curve

  26. Transistor Analyzer Includes: PIC 16F690 DS1803 (digital pot) Max 4610 (CMOS switch) Rotary switch Resistors, op-amps, transistors

  27. Acknowledgments Special thanks must be given to all the individuals that assisted in this Senior Design project. • Advisor – Professor Miller • Advisor – Professor Natarajan • Graduate Student Advisor – Chris Semanson

  28. Questions?

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