Category Archives: Doppler

Measuring Airflow in an HVAC System

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[Nubmian] wrote in to share his experiments with measuring airflow in an HVAC system. His first video deals with using with ultrasonic sensors. He found an interesting white paper that described measuring airflow with a single-path acoustic transit time flow meter. The question was, could he get the same effects with off-the-shelf components?

[Nubmian] created a rig using a pair of typical ultrasonic distance sensors. He detached the two transducers from the front of the PCB. The transducers were then extended on wires, with the “send” capsules together pointing at the “receive” capsules. [Nubmian] set the transducers up in a …read more

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Homemade 6 GHz Radar, v3

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The third version of [Henrik Forstén] 6 GHz frequency-modulated continuous wave (FMCW) radar is online and looks pretty awesome. A FMCW radar is a type of radar that works by transmitting a chirp which frequency changes linearly with time. Simple continuous wave (CW) radar devices without frequency modulation cannot determine target range because they lack the timing mark necessary for accurately time the transmit and receive cycle in order to convert this information to range. Having a transmission signal modulated in frequency allows for the radar to have both a very high accuracy of range and also to measure simultaneously …read more

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Doppler Module Teardown Reveals the Weird World of Microwave Electronics

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Oscillators with components that aren’t electrically connected to anything? PCB traces that function as passive components based solely on their shape? Slots and holes in the board with specific functions? Welcome to the weird and wonderful world of microwave electronics, brought to you through this teardown and analysis of a Doppler microwave transceiver module.

We’ve always been fascinated by the way conventional electronic rules break down as frequency increases. The Doppler module that [Kerry Wong] chose to pop open, a Microsemi X-band transceiver that goes for about $10 on eBay right now, has vanishingly few components inside. One transistor for …read more

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Fail of the Week: Tracking Meteors with Weather Radio

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It’s not hard to detect meteors: go outside on a clear night in a dark place and you’re bound to see one eventually. But visible light detection is limiting, and knowing that meteors leave a trail of ions means radio detection is possible. That’s what’s behind this attempt to map meteor trails using broadcast signals, which so far hasn’t yielded great results.

The fact that meteor trails reflect radio signals is well-known; hams use “meteor bounce” to make long-distance contacts all the time. And using commercial FM broadcast signals to map meteor activity isn’t new, either — we’ve covered the …read more

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Hackaday Prize Entry: Heart Failure Detection Device

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Early and low-cost detection of a Heart Failure is the proposal of [Jean Pierre Le Rouzic] for his entry for the 2017 Hackaday Prize. His device is based on a low-cost Doppler device, like those fetal Doppler devices used to listen an unborn baby hearth, feeding a machine learning algorithm that could differentiate between a healthy and an unhealthy hearth.

The theory behind it is that a regular, healthy hearth tissue has a different acoustic impedance than degenerated tissue. Based on the acoustic impedance, the device would classify the tissue as: normal, degenerated, granulated or fibrous. Each category indicates specific …read more

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The Right Circuit Turns Doppler Module into a Sensor

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Can you buy a working radar module for $12? As it turns out, you can. But can you make it output useful information? According to [Mathieu], the answer is also yes, but only if you ignore the datasheet circuit and build this amplification circuit for your dirt cheap Doppler module.

The module in question is a CDM324 24-GHz board that’s currently listing for $12 on Amazon. It’s the K-band cousin of the X-band HB100 used by [Mathieu] in a project we covered a few years back, but thanks to the shorter wavelength the module is much smaller — just an …read more

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