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7-project_fabrication

7-project_fabrication - Project Fabrication Design Ideas...

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Unformatted text preview: Project Fabrication, Design Ideas, and Other Good Stuff Prof. Greg Kovacs Department of Electrical Engineering Stanford University Time to use this... To design this... Cooltronix Wonder Widget EE122, Stanford University, Prof. Greg Kovacs 2 Reminder: The Design Process • Definition of function - what you want. • Block diagram - translate into circuit functions. • First Design Review. • Circuit design - the details of how functions are accomplished. – – – – Component selection Schematic Simulation Prototyping of critical sections • Second Design Review. • Fabrication and Testing. EE122, Stanford University, Prof. Greg Kovacs 3 Electronic Fabrication Issues • Noise and interference. • Prototyping the circuit. • Packaging. • Labeling + graphics for the prototype. • Demonstration strategies. • Thoughts on manufacturing. EE122, Stanford University, Prof. Greg Kovacs 4 Microsoft Corporation, 1978 EE122, Stanford University, Prof. Greg Kovacs 5 Thermal Noise • Thermal (Johnson) Noise - caused by random motion of electrons due to thermal agitation... e e e e • Every resistor generates thermal noise! Vnoise RMS = 4kTR∆f Vnoise RMS = 1.27 × 10-4 R µV/ Hz • A 10K resistor at room temperature produces 1.8 µV of RMS thermal noise over the 20KHz audio band.... EE122, Stanford University, Prof. Greg Kovacs 6 Shot Noise Bang! • SHOT NOISE • since currents are quantized, their flow is not entirely uniform... • this causes Shot noise.... • a 1 Amp current has 57 nA of RMS fluctuation (NOT TOO BAD!) EE122, Stanford University, Prof. Greg Kovacs 7 1/f Noise • 1/f ("Flicker") Noise • this noise is caused by fluctuations in the actual VALUES of the components (such as the resistance of a resistor) and is dependent upon the applied voltage. • it is expressed in "volts per volt"! • therefore, it depends on the TYPE of component used! • generally, it is also very small, on the order of 10 nV to 1 µV EXAMPLE: RESISTORS (from Horowitz and Hill) FLICKER NOISE OVER ONE DECADE OF FREQUENCY AT 1 V Carbon-composition 0.10 µV to 3.0 µV Carbon-film 0.05 µV to 0.3 µV Metal-film 0.02 µV to 0.2 µV Wire-wound 0.01 µV to 0.2 µV EE122, Stanford University, Prof. Greg Kovacs 8 Interference • INTERFERENCE • noise from outside of your circuit! • 60 Hz pickup is the biggest problem in most situations • RF pickup is also bad! • FOR REAL PRODUCTS, the FCC makes YOU worry about how much interference YOU cause in other products!!! • REMEMBER... IF THE NOISE IS AMPLIFIED, THE PROBLEM GETS A LOT WORSE! EE122, Stanford University, Prof. Greg Kovacs 9 What to Do About EMI • Metal packaging, if properly grounded and interconnected, is very effective. • Conductive plastics and paints are also useful. • Careful attention to signals, connectors, and wires entering or exiting the box is critical: – Shielded cables. – Ferrites. – Capacitors. • Verification of compliance with FCC and international EMI specifications usually handled via consulting firms. EE122, Stanford University, Prof. Greg Kovacs 10 EMI Screens EE122, Stanford University, Prof. Greg Kovacs 11 EE122, Stanford University, Prof. Greg Kovacs 12 Ferrite EMI Suppressor EE122, Stanford University, Prof. Greg Kovacs 13 HP3561A Shielding Note that even the fan is shielded using a metal mesh. EE122, Stanford University, Prof. Greg Kovacs 14 HP3561A Insides EE122, Stanford University, Prof. Greg Kovacs 15 Prototyping Your Circuit • For EE122, the high-frequency plug-boards are adequate in most cases. • Usually, hand-soldered prototypes are best for analog circuits and most closely simulate final performance of a printed-circuit board. • Ground-planed boards are essential for precision, low-noise analog circuits. • Proper power decoupling is ABSOLUTELY KEY one 0.1 µF capacitor per supply rail (to ground) per chip, located as close as possible to the supply pin(s). EE122, Stanford University, Prof. Greg Kovacs 16 Always True - NO!!! Source: Linear Technology AN-47. EE122, Stanford University, Prof. Greg Kovacs 17 Generally True... Source: Linear Technology AN-47. EE122, Stanford University, Prof. Greg Kovacs 18 Typical Digital Prototype - Top EE122, Stanford University, Prof. Greg Kovacs 19 Bottom: Wire-Wrap EE122, Stanford University, Prof. Greg Kovacs 20 Point-To-Point Soldered EE122, Stanford University, Prof. Greg Kovacs 21 Point-to-Point Williams Style Source: Linear Technology AN-47. EE122, Stanford University, Prof. Greg Kovacs 22 Milled Prototype PCB EE122, Stanford University, Prof. Greg Kovacs 23 EE122, Stanford University, Prof. Greg Kovacs 24 Commercial PCB EE122, Stanford University, Prof. Greg Kovacs 25 Surface Mount Components EE122, Stanford University, Prof. Greg Kovacs 26 Grounding and Supply Distribution • Power supply voltages should be distributed using “bus-lines” on the board - on a printed circuit board, these are typically heavy (wide) traces. • Grounding is critical, particularly in mixed-signal systems. • Digital and analog grounds should be kept SEPARATE, coming together at ONLY ONE point the power supply. • Failure to observe this can result in extremely hard to debug ground-related problems. EE122, Stanford University, Prof. Greg Kovacs 27 EE122, Stanford University, Prof. Greg Kovacs 28 Thermal Management EE122, Stanford University, Prof. Greg Kovacs 29 Temperature Probes EE122, Stanford University, Prof. Greg Kovacs 30 Didn’t present your project in class, eh? FIRE !!!! EE122, Stanford University, Prof. Greg Kovacs Got ‘em... It’s Miller time. 31 Any questions? EE122, Stanford University, Prof. Greg Kovacs 32 Packaging Your Circuit • For EE122, building your project in the highfrequency plug-board will be fine. • Of course, you are encouraged to be creative about packaging. • Old food containers, recycled instruments, or even hand-made boxes are relatively easy to organize. • Humor is always welcomed! EE122, Stanford University, Prof. Greg Kovacs 33 Example Prototype Packages EE122, Stanford University, Prof. Greg Kovacs 34 HP5334A - Compartmentalization EE122, Stanford University, Prof. Greg Kovacs 35 Power Digital EE122, Stanford University, Prof. Greg Kovacs Analog 36 Safety - Ground-Fault Interrupters EE122, Stanford University, Prof. Greg Kovacs 37 Fuses EE122, Stanford University, Prof. Greg Kovacs 38 Ergonomics EE122, Stanford University, Prof. Greg Kovacs 39 Layout for High-Speed Circuits Source: Linear Technology AN-47. EE122, Stanford University, Prof. Greg Kovacs 40 HP970A - 1972 • Hand-held digital multimeter. • Integrated rechargeable batteries. • LED display. • Ergonomic design! EE122, Stanford University, Prof. Greg Kovacs 41 HP970A - 1972 EE122, Stanford University, Prof. Greg Kovacs 42 Labeling and Graphics for Your Circuit • A good drawing tool such as Freehand™, Illustrator™, Corel Draw™, or many others can be used to make precise front-panel layouts with a laser printer. • The layout can be printed on sticky-backed transparency material that can be peeled off and applied to the frontpanel of your package. Cepheid TEMPERATURE CONTROLLER Platform Temp. °C Probe Temp. °C Aux. 50°C Power Status 37°C 0°C -15V +5V +15V Reference Select Command Reference Input Output (100 mV/°C) Output To Power Amplifier Aux. Input Turn off system power before removing module. Cepheid, Santa Clara, CA EE122, Stanford University, Prof. Greg Kovacs 43 Scanned Front-Panel for Precise Fit EE122, Stanford University, Prof. Greg Kovacs 44 Overlay Cepheid TEMPERATURE CONTROLLER Platform Temp. °C Probe Temp. °C Aux. Power Status 50°C 37°C 0°C -15V +5V +15V Reference Select Command Reference Output Input (100 mV/°C) Output To Power Amplifier Aux. Input Turn off system power before removing module. Cepheid, Santa Clara, CA EE122, Stanford University, Prof. Greg Kovacs 45 Finished Prototype EE122, Stanford University, Prof. Greg Kovacs 46 Minor Pitfalls... EE122, Stanford University, Prof. Greg Kovacs 47 Demonstration Strategies • Demonstrations are intended to: – Demonstrate the technical features of a product. – Excite potential customers (or graders!). – Sell hardware/software (if in the real world). • Good demos are: – Concise - attention spans are limited. – Clear - no confusing stuff. – Organized - progress clearly from front-end to back-end. • Suggested strategy: – – – – – – Introduce team. Explain purpose of device. Explain how it works. Demonstrate it working. Summarize. Ask if there are questions. EE122, Stanford University, Prof. Greg Kovacs 48 THE FINE ART . OF . .. MARKETING.... EE122, Stanford University, Prof. Greg Kovacs 49 Thoughts on Manufacturing • In production, circuits are optimized for cost. • In some domains (e.g., consumer), performance can be traded off quite freely for savings. • In other domains (e.g., precision instruments), peformance goals tend to be fixed. • “Discretes are free.” - true to some extent. • Automated, low-cost assembly is typical. • Economies of scale rule. • Testing and rework strategies are valuable. EE122, Stanford University, Prof. Greg Kovacs 50 POWER AMPLIFIER COST (\$) PRODUCTION: COST VS. QUANTITY 0.08 1N4001 DIODE COST (\$) 11 0.07 POWER AMPLIFIER CHIPS 10 9 8 DIODES 0.06 0.05 0.04 0.03 7 0.02 10 0 10 1 10 2 10 3 10 0 10 1 10 Quantity 10 3 10 4 10 5 Quantity 0.18 0.060 1/4W 5% RESISTOR COST 0.16 0.14 0.12 0.10 CAPACITORS 0.08 0.06 0.04 10 0 10 1 10 2 10 3 0.050 0.040 RESISTORS 0.030 0.020 0.010 10 4 Quantity EE122, Stanford University, Prof. Greg Kovacs 0.000 (\$) CAPACITOR COST (\$) 2 10 0 10 1 10 2 10 3 10 4 10 5 10 6 Quantity 51 ...
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