Right, another chip teardown. I'll get this done quickly.
Abstract:
This video focuses on the Hewlett-Packard (now Agilent/Avago/Broadcom) HEDS-1000 emitter-detector system, a specialized component the creator has fond memories of from their early career. The HEDS-1000 is essentially an integrated, hermetically sealed barcode sensor containing both a custom-shaped, circular 700nm Gallium Arsenide LED and a silicon phototransistor, coupled with specialized bifurcated lenses. The complexity lies in the precision optics required to focus the emitter light onto a specific spot and collect the reflected light onto the detector, utilizing tilted optical axes. The creator highlights how this device profoundly influenced their career path toward optics and specialized electronic design. A brief functional demonstration using a printed pattern shows the expected low/high signal response on an oscilloscope, confirming its operation as a reflective light sensor.
Chip of the Day: HEDS-1000 Barcode Sensor Analysis
00:00:08 HEDS-1000 Component: The featured chip is the Hewlett-Packard Emitter Detector System (HEDS-1000), a component that significantly influenced the creator's early career appreciation for combined optics and electronics.
00:00:53 Functionality: It is a non-contact reflective sensor, operating around 700nm, designed primarily for barcode reading but usable for other measurements.
00:01:35 Hermetic Packaging & Internal Components: The unit is hermetically sealed. Internally, it contains a custom Gallium Arsenide LED (designed to emit a perfect circle of light) and a photodiode/transistor combination (photo-transistor), along with two specialized lenses and a window.
00:03:52 Specialized Bifurcated Lens: The critical feature is the bifurcated lens system. It comprises two lenses whose optical axes are slightly tilted relative to each other, allowing both the emitter and detector to focus light onto the same spot.
00:04:45 Career Significance: This device demonstrated the power of custom, integrated optical/electronic solutions beyond simple imaging, driving the creator towards specialized optics engineering.
00:05:35 Internal Assembly Details: The system uses the photo-transistor configuration to multiply the photodiode current (beta $\approx 200$).
00:06:19 Specifications: LED drive is about 35mA; photodiode current is about 140nA.
00:06:45 Application Context: Historically designed, in part, to input programs into the HP-41 calculator via scanning printed barcodes from books.
00:07:42 In-Circuit Test: A demonstration shows the emitter projecting two spots (due to the bifurcated optics). Waving a patterned card across the spot yields the characteristic high/low signal variation on an oscilloscope when AC coupled.
00:08:55 Noise Observation: The scope signal shows significant 120Hz ripple when exposed to room light, indicating pickup from AC-powered lighting that the sensor/amplifier chain is sensitive to.
00:10:09 Creator Reflection: The component represents a confluence of interests (software, electrical engineering, optics) that led the creator to focus almost entirely on optics later in their career.