Low-Cost Rapid Prototyping of Electronic Circuits

Low-Cost Rapid Electronic ProtoypingÌý(REP) Initiative:

These projects leverage and evaluate various best practices of building low-costÌýcircuits in the shortest time using:

A sequential phased approach as risk reduction:

  1. phase 1: plug and play
    • develop and verify the circuit design
    • build with off the shelf modules
    • uses external power
    • use break out boards and solderless breadboards.
    • characterize the components
    • start writing the code
  2. Phase 2: "shield" version
    • design and build custom PCB for the components with digital interface to the uC
    • uC uses COTS dev kit or board
    • tests the circuit board version of the circuit design
    • separate power conditioning module based on final implementation
    • finalize the software
  3. Phase 3: fully integrated custom circuit board
    • uC and all the electronics are integrated on one board
    • power conditining is integrated into the single board
    • some components maybe on replaceable modules for repair or upgradeÌý

This initiative also includes best practices for rapid bring up, debug and test, using methods such as:

  • leveraging datasheets, reference designs eval boards and dev kits
  • using COTS plug and play modules
  • using dev kits and eval boards as needed
  • using small breakout boards for component evaluation and converting SMT to through hole parts
  • includingÌýfeatures just for testing: test points, indicator LEDs, labels, and isolation switches
  • modular design with interconnects (cables, connectors, header pins, flex strips, etc.) between modules vs fully integrated on one board
  • fully integrated PCB with all the components
  • best measurement practices with scopes and other instruments

To implement these phases will require skill in the following methods:

  • solderless breadboards with best wiring practices
  • turning a solderless breadboard into a soldered circuit board with the same conductor pattern in the circuit board as the SBB
  • conductive ink printed interconnects with:Ìý
    • a blank board andÌýbottom ground plane, with pre-patterned ground pads on the top or making vias to the ground using drilled holes and filled with conductive ink
    • a pre-patterned board with IC footprints and their fan out and ground vias with just customized routing- like a gate array
    • a kapton sheet to make flex circuits
    • printed dielectric materials for automated 2-layer printing or nail polish for manual 2-layer printing
    • direct attach of components by the conductive ink adhesive or other conductive adhesive
    • direct attach of components by soldering to the silver based inks
  • low costÌýoff-shore circuit board fab and in-house assembly:
    • with manual soldering of components to the board with soldering iron
    • with voltera solder paste dispense or screen printing solder paste followed by reflow oven
    • with manual placement of parts on solder paste pads or semi-manual pick and place instrument for fine pitch, QFN or BGA parts
    • using standard FR4 and flex substrates
    • using gold pads on one side as electrodes and circuitry on the other side for co-located analog front end processing
    • using circuit boards as non interconnect structures, such as sensor arrays with inter digitated combs, via and rings for local capacitor sensing, windings for rf pick up and inductive charging, integrated antennas, stepper motor coils, etc with multiplexers to connect X-Y channels to sense electronics, as needed
  • low-cost off-shore suppliers for fab and assembly using their parts or third party kitted parts
    • using standard FR4 and flex substrates
    • from vendors such as PCBway and JLCpcb

Ìý

    Circuit boardsÌýto be built using these methods, includeÌý

    (see as examples the .)

    1. assembly demonstration test boards also illustrating best design principles:
      • through hole connectors and ribbon cables showing ground bounce in connectors and ribbon cables using good and bad return path patterns, driven by the I/Os switching from an Arduino board
      • SMT assemblyÌýof LEDs and resistors
      • a golden arduino board using a leaded 328 and a QFN 328 with good and bad connections off board
      • assorted breakout boards for SMT footprints to DIP footprints for use in solderless breadboards
    2. assorted uC breakout modules: Microchip (AVR and SAMD21, 51), Nordic (ESP32), TI, Silicon Labs (Gecko), others
      • check out the series of Xiao modules
      • the from Adafruit
      • the dev kits
    3. Assorted fully custom uC modules with selected uCÌý
      • AVR series like the atmega 328
      • SAMD21 series like a QT-PY
      • NordicÌý
      • Expressif like ESP32
      • Silicon Labs like the Gecko
      • ATiny for ultra low power and small size
      • Use a form factor like a USB stick that plugs directly into a USB port and adds some special function
    4. modules to use with uC- either as separate modules or integrated on the same board
      • GPS position tagging add on moduleÌýto a uC
      • rf telementry communication: zigbee, rf, BLE, wifi, cell network added to any uC
      • lidar with a servo or rotating interface for 2D mapping
      • rf ID tages
      • TI has a series of single-chip 77 GHz radar transceivers and phased array radar antennas Ìý
      • simple camera with image processing and AI or ML software
      • two camera and parallax, 3D reconstruction transmitted over bluetooth or WiFi
      • Simple FM transmitter asÌýway of transmitting data from a sensor node to another FM receiver, .
      • Transmit telemetry data from one ESP32 to another using WiFi and .
      • DC motor control, H bridges and PWM and uC drivers, stepper motors, with encoder feedback
    5. self organizing mesh architecture of sensor nodes by rf with a local hub
    6. Power related:
      • Plug power based DC to DC SMPS buck regulator from 100 mA to 5 A and LDO or linear for lower noise with integrated insitu current sensing
      • inverters for negative supplies with LDO for lower noise
      • energy harvester boostÌýfrom dead battery, or wind, or solar, or rf fields to charge a battery or super capacitor,Ìý, and like these , or like these parts;Ìý Ìýor , or this one or this oneÌý.
      • Solar panels for energy harvesting- selections, efficiencies, charging circuits
      • various batteries, both primary or rechargable
      • power over ethernet (POE)
      • a small module that plugs into the end of a SBB and supplies +/- 9 V, 5 V regulated and 3.3 V regulated from a 5 V input- either from power plug or USB power
    7. Analog front ends:
      • Evaluate instrumentation amplifiers and negative power supply inverter from a positive supply, w, wo LDO for lower noise l:Ìýto provide bipolar power
      • lowest noise pre-amp with chopper stablizied for low drift and ultra low noise input with < 1 nV/rt(Hz) for a noise spectrometer
      • Use an analog front end interface such as the neuromuscular interface as an input device and some response as the output.
      • fast ADC with onboard memory buffer to turn a simple uC into a fast scope front end like digilent AD2 or Red Pitaya that takes data quickly and dumps it into local memory in real time.
    8. Sensors:
      • Check out this optical spectrum analyzer:Ìý
      • Sensor board with a variety of COTS sensors: voltage outputs, resistance outputs, I2D and SPI outputs
      • Example of
    9. oscillators and clocks
      • local clock phase locked to a local atomic frequency standard or from the NIST 60 kHz signal or GPS signal
      • examples of multiple oscillators such as opamp RC, inverter ring oscillator, inverter and crystal, DDS based on a crystal, uC I/O based on a crystal, crystal with up converter or down converter with counter
      • Precision function generator using a DDS chip like a AD9834 with crystal stable frequency
      • real-time, time stamping added to any measurement with nsec accuracy tied to NIST time
      • RLC circuits as feedback elements in inverters
      • using a uC as a frequency counter- what is the stability? how else to measure stable freq: zero crossing, phase interpolation, sine wave fitting, etc.
      • a simple freq counter wtih Alan variance plotting as output by comparing the beat freq between reference source and signal under test.to get higher accuracy. Use double balanced mixer
    10. Component characterization:
      • measured performance against the datasheet specs
      • evaluating a good candidate to add to favorites list and add to inventory stock
      • create a breakout board to use in solderless breadboard
      • applied to op amps, TVS diodes, transistors, MOSFETS, polyswitch fuses, sensors, inverters, oscillators, SMPS, multiplexers (analog switches), relays, etc.