RAK811 3D model and plastic housing

There was no3D model for RAK811 breakout board with GPS tracker, so I made it from the drawings. I added plastic housing to be used with velcro straps. I prepared two models, one with only RAK811 and small LiPo battery and second one, 4mm higher with enough space for additional PCB with custom electronics. Enjoy.

Higher version with additional PCB

Lower version without additional PCB

Base is same for both versions.

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LoRa module in DIL form

Murata produces LoRa module CMWX1ZZABZ-xxx based on SX1276 transceiver and STM32L072CZ microcontroller. The soldering of the LGA module is not very hobby-friendly. I constructed small breakout PCB for this module with additional buck/boost switcher and place for SMA connector. The transceiver features the LoRa®long-range modem, providing ultra-long-range spread spectrum communication and high interference immunity, minimizing current consumption. Since CMWX1ZZABZ-091 is an “open” module, it is possible to access all STM32L072 peripherals such as ADC, 16-bit timer, LP-UART, I2C, SPI and USB 2.0 FS (supporting BCD and LPM), which are not used internally by SX1276.

LoRa breakout board

 

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Quick and dirty 868MHz antenna in 5 minutes

This is simple antenna for 868MHz built in 5…10 minutes. Take about 10cm of RG214, a plate of PCB with the copper at one (or both) sides. Remove the coax shield and inner dielectric on one side in length of about 85mm. You will cut this to proper length during SWR measurements.

Simple antenna made with piece of coax and piece of old PCB.

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Multisensor LoRa Device

The described device is nearly matchbox-sized board (50 x 24 mm) packed with sensors. Auxilary board is 10x50mm with additional sensors. The module is developed around the Murata ABZ LoRa module, which integrates STM32L072 and samtech SX1276 in tiny 12.5 x 11.6 x 1.76 mm package. The main board is equipped with following sensors:

  • Magnetic compass MAG3110
  • Thermometer TMP75 for internal temperature measurements
  • MPU unit is MPU6050
  • RH and temperature sensor Si7013

Small section of the main board can be separated. There aqre 6 sensor on this part of the PCB:

  • Thermometer TMP75
  • RH sensor SHT31
  • RH, T and pressure sensor BME280
  • Another Si7013 for external RH and T measurement
  • Ambient light sensor VEML6030
  • UV sensor VEML6075

There are two 1Mbit EEPROMs on-board for local data logging. Additional pins are available for SPI, 2x UART and I2C interface, where even more sensors can be attached.

LoRa multisensor module

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Collinear antenna for 868MHz Lorawan Gateway

This is description of coaxial collinear antenna for 868MHz applications. I designed this for Lorawan gateway.

Antenna tested with lorawan gateway

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Low cost single cell battery pack simulator

Modern battery operated portable devices use smart battery packs. Every new development of an electronic medical device must follow strict design flow defined by world-wide or local regulatory
directives. The development process of any such device using smart battery pack requires specific operating conditions to meet the testing criteria. When smart battery pack is one of the main power sources the host system should be tested with several battery states. The testing is necessary during development, validation and later in production testing.

Battery simulator block diagram

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Radar under 20€ using cheap CDM324 24GHz doppler module

You can get CDM324 module on ebay for about 6€. It is constantly transmitting and receiving at 24GHz. It’s output is the difference between transmitted and received signal frequency.

I made a simple PCB with opamp, analog comparator and a powerful MCU STM32F4. Besides that, there are some other peripheral components. The PCB connects to the module with 3pin header. On the PCB, another PCB with small joystick is soldered. This joystick is used to interact with GUI on 128×64 graphic OLED display. The main PCB also has USB connector for virtual COM port and charging of 240mAh lithium battery.

Render of the device

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Voluhar project – 3 axis camera stabilization

The Voluhar project will be / might be open hardware and open software project for any DIY and videographer enthusiast that would like to get those enviably steady smooth shots. Well, for now this statement is a bit of a long shot since I don’t really know what I don’t know about brushless gimbal systems.

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Multicolor signal light with beeper

When debugging algorithms in an autonomous vehicle a light that can show algorithm state in real time was proven to be effective for easier debugging and additional insight to what is going on in the code.

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Tiny, isolated USB to Xcvr interface (PTT, Audio, CAT, …)

I will descvribe here the USB interface between the redio station and the computer which I recently developed and tested. This post is a continuation of the first part, where I described a simple interface for controlling two digital lines using the USB / Serial Converter, where I presented simple interface to control two digital signals (e.g. PTT and CW). This time I will describe an interface that combines more functions:

  • Controlling several digital (switching) inputs and outputs,
  • Interface for controlling the station via the serial interface
  • Audio input and output interface (sound card)

I had some implementation issues with the microcontrollers and USB virtual com ports, which I have described in detail in the previous contribution, I decided it’s better using the tested solutions. The block diagram of the interface is swhown in following picture:

Block diagram of the interface

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