Electronic design services for
analog, digitally-controlled analog and digital systems
for audio, data acquisition, filtering and signal processing.

schematics, pc boards, prototypes or production, product graphics and documentation

Experience with telemetry signal processing, digital frequency synthesis, analog-digital conversion, PLCs, lasers & optics, robotics, infra-red sensors, operational amplifiers, low-power and low-noise circuits, power MOSFET controls, analog and digital multiplexers, demodulation methods, semiconductor wafer handling systems, thermo-electric cooling systems, and programmable analog filtering techniques, agricultural sensing and control systems.

Seventeen Port (5x12) MIDI Thru Box

This piece of rack-mounted MIDI gear was created for Emerald Music, and incorporates U.S and European power supply on the board. Two independent THRU box components provide a versatile, uncomplicated interface to interconnect multiple audio synthesizer modules, while avoiding timing delays and noise degradation.
Plant Sensor Prototype PCB for second generation real-time spectral analyzer for assessing plant biomass.
Valve sequencer for LDSL passenger cars (Amtrak) has interval programming Valve sequencer for LDSL passenger cars (Amtrak) can be programmed via menu for 100ms time intervals for accurate fluid control.
Sequence controller regulates from 100VDC in down to 24, 12 and 5V

Slaved sequencer is controlled via two-line handshake protocol and includes customer-required card-slot interface

RS-232 Serial test fixture Compact RS-232 Serial test fixture uses a VFD
High-Speed Single-Axis Robotic Arm is Vehicle-Mounted (for CalTrans)

A robotic arm to sense and avoid obstacles while automatically spraying roadside weeds. Subsystems include: a PLC for timing, InfraRed object sensors, a doppler radar ground-speed, magnetic safety interlocks, and a 48V servomotor which drives the arm. Optical sensors in the spray heads activate upon detecting chlorophyll.

The arm rapidly retracts (0.5sec) to avoid obstacles at the side of the road.

LED optical output power test stand Proprietary test fixture uses ABS optical column with a photodetector amplifier at the base for measuring and sorting LEDs by output power
Solenoid Valve Sequencer

A multiple stage linear/switching regulator configuration yielded 5V operation from a 50-100VDC input for rail application. [Evaluation prototype board pictured].


Semiconductor Wafer Detector

An array of tiny sensors detect the presence of silicon wafers in a robotic handling system. the interface board provides the position decoding for up to six sensor array stages.  
General Purpose IO controller with multiple conditioned inputs and outputs General purpose input/output controller has 8 channel mosfet source-drive outputs, and includes circuitry for peripheral stepper-motor controlling .

Flashing Headlights for a Locomotive

A locomotive mounted controller which activates two headlights continuously, or flashes them alternately for a specific period of time when traversing a railroad intersection.

The interesting part was finding a way to survive the occasional times when a bulb burns out; this requires the controller to handle more than 10,000 Watts (a current pulse roughly twice that required to start a car).

Bit Synchronizer for Telemetry Data with a 1,000,000 to 1 Range



A significant development effort resulted in two cards (reduced in size about 20x) which performed the input level-shifting and filtering of a data stream, synchronized to it with a real-time phaselock servo, and reconstructed a clock signal from it.

The Bit Synchronizer operates from 10Hz to 10MHz. (Several years later, the same basic design is still being enhanced for speed and size.)

Fire-fighting Robot Controller Four Microchip 16F series microcontrollers combine to interpret remote control receiver signals to drive the 40A motors and turret-positioning servos of this fire-fighting robot.  
Signal Routing Matrix
A wide-band analog multiplexing system for multi-track data recorders and general-purpose large-amplitude signals. An internal monitor displays the selected routing paths for each input.
Photo-detector amplifier for precision evaluation of I/R LEDs A client's requirement was to measure the output of LEDs into a custom test fixture to monitor output illumination. Constant current drive of the LED, and an extremely high-gain amplifier coupled with a 6th-order filter achieved the required sensitivity.

Programmable Anti-Aliasing Filter for a Real-time FFT Processor

A fourth-order analog Low Pass filter using a Sallen-Key topology (much faster than an equivalent bi-quad implementation) is digitally programmable from 10Hz to 320kHz.

This anti-aliasing filter operated in front of an FFT processor.

This concept was used again later (with faster opamps and switches) to achieve a tunable LPF ranging from 10Hz to 10MHz! The op amp used was National's LM6361. Even better amps are available now.

Digital Answering Machine A proof-of-concept circuit implemented a five message answering machine using a PIC16F84 microcontroller, an ISD2512 voice-record chip, and some external registers.

Voltage-Controlled Schmitt Trigger

An analog voltage comparator circuit whose switching hysteresis is voltage-controllable. (Published in Electronic Design magazine.)  
Frequency Measurement board interfaces to PLC Adding this board eliminated more than a hundred manual interconnects and integrated a PIC-based frequency counter to indicate traveling speed in the cab of a train.
Switchable Load Fixtures

Simple, practical load test fixtures use power resistors and automotive headlights respectively.


ATmega ruggedized shield interface Ethernet input to Atmel microcontroller provides control and drive circuitry to multiple solenoids on agricultural vehicle.
Emergency Brake (Crash-Prevention Circuit) for semiconductor wafers In the event of a computer malfunction or a power failure, this circuit gently brakes a vertical-axis robotic arm for silicon wafer handling. It must function without primary power, guarantee no high vibration or sudden movements.
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Sequencer/Controller for custom ag machine Prototype tractor-mounted controller based on PIC microcontroller interfaced to existing agricultural sensors

Additional Devices

  • Portable wide-range Inductance meter measures inductances up to 1000mH.
  • PIC-controlled Speed sensor uses PIC16F873/876 as a Period/Frequency meter
  • Hand-held unit is a dedicated RS-232 test fixture
  • Multi-rack modular production test system uses IEEE-488 (GPIB) network to sequence and log RF Synthesizer performance
  • Ultra-low noise temperature transducer amplifier for robotic arm to prevent accidents in silicon foundry
  • Custom Active Electronic Crossover for audio system
  • Emergency Brake for the servo-motor of a semiconductor wafer handler
  • Semiconductor Optical Wafer Position Detector
  • 10-bit programmable One-Shot Timer with microsecond resolution
  • Digitally-Tunable Active Filters are Orthogonally Tuned across 10 octaves
  • Frequency Synthesizer using discrete logic with operating range from 100Hz to 90MHz
  • Amplitude Modulated Time Code Generator/Translator for missile telemetry
  • Automatic test system checks 12V components for compliance to over-voltage and reverse voltage to specifications
  • Board controller monitors air and water pressure, vacuum level and sequences up to five subsystems for Amtrak Passenger Car
  • Real-time Delay controller oeprates 16 channels on trains for BSCF Railroad (France)
  • Programmable fourth-order FFT Anti-Aliasing Filter
  • Voltage-Controlled Schmitt Trigger (published)
  • Direct digital Pulse Width Modulator (published)
Examples of software analysis, calculation and interface tools, code and outputs

Some of these circuits were designed while a staff engineer, others as an independent consultant.