Contact: info@pavlin.si
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.
Continue reading ‘Quick and dirty 868MHz antenna in 5 minutes’ »
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:
Small section of the main board can be separated. There aqre 6 sensor on this part of the PCB:
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
This is description of coaxial collinear antenna for 868MHz applications. I designed this for Lorawan gateway.
Antenna tested with lorawan gateway
Continue reading ‘Collinear antenna for 868MHz Lorawan Gateway’ »
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
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
Continue reading ‘Radar under 20€ using cheap CDM324 24GHz doppler module’ »
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.
Continue reading ‘Voluhar project – 3 axis camera stabilization’ »
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.
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:
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
Continue reading ‘Tiny, isolated USB to Xcvr interface (PTT, Audio, CAT, …)’ »
In this post, I will first introduce some of the basic technical background of the control of the transmit signal (PTT) and other signals (eg CW or linear activation). The second part will describe the interface development and the final product.
Standard DB9 male connector
Photoelasticity is wonderfull phenomenon. It describes changes in the optical properties of a material under mechanical deformation. It is a property of all dielectric media and is often used to experimentally determine the stress distribution in a material, where it gives a picture of stress distributions around discontinuities in materials. Photoelastic experiments (also informally referred to as photoelasticity) are an important tool for determining critical stress points in a material, and are used for determining stress concentration in irregular geometries. [https://en.wikipedia.org/wiki/Photoelasticity]. Experimenting with photoelasticity photography gives some nice photos at least. It is usefull tool for visualisation of the internal stresses within (transparent) material.
My experiment setup:
Photoelasticity photography setup