A speed sensor that uses the Doppler effect - with display

CDM324 Doppler Speed Sensor - Arduino Compatible

Sold by Stephan Electronics


No tax for United States [change]
Displays detected speed on the sensor
Connects the sensor to your computer
Isolates USB communications for better noise performance - only with expansion board
Stock available: 903


CDM324 Doppler modules you can find on eBay need additional electronics to be operated. This listing therefore offers a CDM324 with its speed sensing board, which contains all the necessary components and even a display/expansion board (if selected).
To make it work, simply apply 5V and you're good to go!

Input & Output Signals

2 expansion connectors provide access to the following inputs/outputs:

  • spare SPI and I2C bus
  • 5V / 50mA power input
  • digital input for MPH / KM/H selection
  • raw DC-coupled CDM324 amplified output
  • nRESET / BOOT0 signals for MCU programming
  • UART bus for speed query & MCU programming

For more technical specifications and testing, have a look the dedicated webpage.
The CDM324 conforms to ETSI #300 440 (Europe), its 24.125GHz operating frequency is included in the IARU 1 & 2 Regions (Americas & Europe).
Please make sure that this Doppler sensor follows your country regulations.

Expansion board

The expansion board connects to the main device to offer the following features:

  • a USB to UART converter, connected to the RESET & BOOT0 lines
  • a switch to toggle between MPH and KM/H display
  • a jack connector to listen to the Doppler sound
  • a uSD card connector for data logging

Together with stm32loader or our framework, one click firmware updates are possible using the RTS & DTS lines of the USB-UART converter:

Python framework & visualization tool

A python user interface is available on our repository and can be used when connecting the speed sensor to your computer using a USB-UART adapter or our expansion board.
Note that the firmware update feature is only available when using our expansion board.
In this framework is also included the above tool (Windows only) to get advanced speed data information.

Speed measurement capabilities

Speeds from 3.4km/h to 180km/h, (2.1mph to 112mph) may be measured.
Sensitivity will depend on the sensed object size and material, as metallic objects reflects RF waves much better than organic materials.
Please have a look at the video below to get an idea of what the sensor can do.

[This video content is unavailable on this device]

USB isolator

Given the extremely high amplification used, in some cases the noisy power supplies present in old computers and laptops may generate some unwanted spikes in the amplified spectrum, as can be shown below:

As a way to potentially mitigate this issue when connected to the sensor through USB, you may add a USB isolator to your purchase.

Links to code and documentation

Documentation (limpkin.fr)

Code (github.com)

Design Files (github.com)

Schematics (github.com)

Bom (github.com)

Shipping policy

All of our devices are shipped from Shenzhen, China. It takes between 2 to 3 weeks to receive your order.

The seller

Stephan Electronics

Lausanne, VD, Switzerland
46 orders since Apr 4, 2022
From the creator of www.limpkin.fr, this shop lets you buy different open hardware projects.