tCam-Mini : Open Source Wireless Thermal Imaging Module based on Flir Lepton 3.5 and ESP32

tCam-Mini is a wireless thermal imaging module based on ESP32 and FLIR Lepton 3.5 Infrared camera module. The open source project is created by Dan Julio and was crowd funded through Hackster Launch and GroupGets.
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tCam-Mini Thermal Imaging Module. Image source: GroupGets

tCam-Mini is a wireless thermal imaging camera designed by Dan Julio from Colorado, USA. The fully open source project is based on Espressif’s ESP32 Wi-Fi module and FLIR‘s thermal imaging camera module Lepton 3.5. tCam-Mini was crowd funded and launched through Hackster Launch programme by Hackster.io and GroupGets. The project was successfully funded and the campaign ended on 07 April 2021. As the name suggests, tCam-Mini is a smaller subset of the fully featured design called tCam which is currently under development. The project is completely open source and the hardware and software files can be downloaded from Dan’s GitHub repository. The firmware is written using ESP-IDF and can be flashed to the module via USB.

Lepton 3.5 has 19,200 (160×120) pixels that can capture IR radiation in the temperature equivalent range of -10˚ to +400˚C. It has a form-factor and mechanical interface to be easily installed onto a side-contact socket. The tCam-Mini is a carrier and processor board that has a compatible socket for Lepton 3.5. You have to buy the camera module separately when you buy the tCam-Mini. You can buy tCam-Mini and camera modules from GroupGets store.

Features of tCam-Mini

  • The tCam-Mini camera exposes the full capabilities of the Lepton.
  • The camera can operate in either Radiometric/TLinear (each pixel contains temperature data) or AGC modes (no temperature data in each pixel but better images).
  • Simple json-based command set with communication of a TCP/IP Socket. Makes interfacing with the camera very simple from a custom application.
  • AP or STA (client) Wifi modes (static or DHCP-served IPV4 address).
  • Single image or streaming data modes.
  • Control over sensor emissivity, gain and spotmeter location.

Hardware Overview

  • Espressif ESP32-WROVER-E Module (ESP32-D0WD0V3, 8 MB PSRAM, 8 MB Flash) with built-in antenna
  • Flir Lepton 3.5 (160×120 pixel radiometric LWIR camera with shutter)
  • CP2102N-A02 USB to UART bridge with ESP32 boot loader control
  • Multi-voltage power supply (3.3V, 3.0V, 2.8V, 1.2V)
  • Dual color (Red/Green) status LED
  • Factory Wifi Reset button
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tCam-Mini PCB Top. Source: GroupGets
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tCam-Mini PCB Bottom. Source: GroupGets

tCam-Mini also comes with a companion software that run on Mac OS, Windows and Linux.

Features of Companion Software

  • Display images or streams with multiple palettes.
  • Save and load images or streams in files preserving the radiometric data for use later or by other applications. Two file formats: image and video (described in the github repository).
  • Export images as jpg, png or tiff files.
  • Copy current image to computer’s clipboard.
  • Histogram display and analysis of pixel populations.
  • Spotmeter and up to four additional markers showing temperature at various points in an image.
  • Graphing function to plot spotmeter and marker data over time.
  • Graph baseline mode to allow comparing temperatures to a reference point in the scene (for example to compare a temperature to a blackbody constant).
  • Export graph data in a text file for analysis by other programs.
  • Print graph (or create a PDF on computers that can print to PDF).
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tCam-Mini Companion Software
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tCam-Mini Thermal Imaging Module in action

Infrared Radiometry and Lepton 3.5

Flir Lepton 3.5 is a radiometric capable Long-Wave Infrared (LWIR) camera module from the Lepton series. It functions just like a camera module inside a smartphone but captures light in the Infrared (IR) region of the electromagnetic spectrum. The wavelength of light in this range falls between 8 µm to 14 µm. Ordinary camera modules measure the intensity of three ranges of wavelengths namely Red, Green and Blue (RGB). The intensity values are converted to a digital format to create a digital image that can be displayed on an RGB display. Unlike that, each pixel in a thermal imaging camera captures IR intensity and is calibrated to output the temperature of the object it is seeing. Such a device is called a Bolometer. The resulting image is typically a monochrome image. This image is then added with false colors of the RGB range so that the gradients of temperatures are better perceivable to us. This is the type of high contrast RGB thermal images we are familiar of seeing.

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Flir Lepton 3.5

Specifications of Lepton 3.5

  • Sensor Technology: Uncooled VOx microbolometer
  • Input Clock: 25-MHz nominal, CMOS IO Voltage Levels
  • Field of View: 57° (nominal) HFOV, 71° diagonal (f/1.1 silicon doublet)
  • IR Wavelength Range: 8 µm to 14 µm
  • Thermal Sensitivity: < 50 mK (0.050° C)
  • Image Optimization: Integrated digital thermal image processing functions, including automatic thermal environment compensation, noise filters, non-uniformity correction, and gain control
  • Radiometric Accuracy:
    • High Gain Mode: Greater of +/- 5°C or 5% (typical);
    • Low Gain Mode: Greater of +/- 10°C or 10% (typical)
  • Scene Dynamic Range:
    • High Gain Mode: -10° to +140°C
    • Low Gain Mode: -10° to +400°C (at room temperature), -10° to +450°C (typical)
  • Solar Protection: Integral
  • Radiometry software features for temp measurement including per pixel and frame radiometric output (TLinear) and Spotmeter
  • Pixel Arrangement: 160 (H) × 120 (V) active pixels with progressive scan
  • Pixel Size: 12 micrometers
  • Output Format: User-selectable 14-bit, 8-bit (AGC applied), or 24-bit RGB (AGC and colorization applied)
  • Frame Rate: 8.7 Hz (effective)
  • Video Interface: SPI
  • Control Interface: CCI (I2C-like), CMOS IO Voltage Levels
  • Supply Voltage: 2.8 V, 1.2 V, 2.5 V to 3.1 V IO
  • Power Consumption:
    • 150 mW (operating)
    • 650 mW (during shutter event)
    • 5 mW (standby/shutdown)
  • RoHS compliant
  • Mechanical Interface: 32–pin socket interface to standard Molex® socket
  • Size (W x L x H): 10.50 x 12.70 x 7.14 mm
  • Weight: 0.9 grams

More information on Lepton 3.5 and compatible development hardware can be found at this GroupGets post. tCam-Mini costs $64.99 and Lepton 3.5 costs $199.00 at GroupGets store.

Links

  1. Flir Lepton 3.5 – Product Page
  2. Flir Lepton 3.5 Datasheet – PDF
  3. tCam-Mini – GroupGets Campaign Page
  4. Buy tCam-Mini – GroupGets Store
  5. Buy Flir Lepton 3.5 – GroupGets Store
  6. Buy Flir Lepton 3.5 – DigiKey
  7. tCam-Mini – GitHub Repository
  8. More information on Lepton 3.5
  9. ESP32-WROVER-E Module Datasheet – PDF
  10. Hackster Launch Programme

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Vishnu Mohanan
Founder and Chief Editor at CIRCUITSTATE Electronics
Articles: 36

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