What is inside plastic?

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

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6×1 antenna switch

This is complete project for 1×6 antenna switch. It was bult in more than 50 pieces around the world and performs really good. Even big guns use it for their systems. The project was designed with help from other OMs (S55O, S59MA, S50LD, S51CT, S51ZJ, SM2WMV/SJ2W and others).

6×1 antenna switch

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Cheap sh*t magnetic pickup

Do you ever wondered how much magnetic field garbage is around you? This is cheap and easy build to measure magnetic noise or to compare which switching supply is more sh*tty.

Near field probes are nothing new. It’s easy to find one via web search. Here is one good reference for H and E field probes which I found via google image search:

EMC near field probes for H and E field

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From c source to cloud with ESP8266

There are many steps from c source code to cloud data storage. Let’s start…

“To get the end, you must go back to the start” – Grandmother Yelsh

In this contribution I will describe how I started using Espressif ESP8266 with Eclipse and some other details how to store data in “usual” web server. I will not talk about the hardware too much. To follow the tutorial it is enough to have any ESP8266 module connected to serial port on PC either via USB/UART virtual cvom port or directly (rare these days). Two most common possibilities are either module with the USB/UART integrated on-board or separated USB/UART + ESP8266-xx module (usually on breadboard with some additional periphery):

Two most common types of dev.boards for ESP8266

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Precision voltage source – voltage calibrator

_________________ Work in progress _______ Last change: 22.10.2017 ______________

 

What I missed in my workshop is nifty small programmable precision voltage source which can be used as calibration voltage source for testing and calibration purposes. I decided to make one, because instruments which have word “calibrator” have price with same digits as there is vocals in this magic word.

Let’s start with block diagram:

Voltage calibrator – Block diagram

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Altium – working with embedded boards

Embedded board arrays in altium could be used for creating panels for multiplication during prototyping. Here is short illustrative example. In this example we will:

  1. create single PCB board design (not covered here)
  2. create and embed array with this single PCB
  3. add some markers and holes
  4. add panel cutouts

Final result, keep reading below…

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PRECIsion Power SUpply project

PreciPSU is an attempt to build high performance power supply. The idea started few years ago but it was never realised. Some major target performance specs are as follows:

  • three isolated channels
  • around 50W per channel
  • 24V/3A output per channel
  • lowest possible ripple at fastest response
  • small size
  • programmable via USB
  • nice housing with minimalist user interface (2 plugs per channel, knob, button and small display

Update 15.7.2017: block diagram

PreciPSU Block diagram

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Adjustable gain LNA

Low noise amplifiers are very useful. I built one with single BFG425W transistor with adjustable bias current. The schematic diagram is very simple:

LNA schematic diagram

and the PCB is 20x24mm:

LNA PCB

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Smart nesting box

Smart nesting box is small wooden box for nesting birds. It is equipped with the live camera feed and some sensors. Four smart nesting boxes were made and three of them were placed in the wild. One was inhabited with the great tit in te early march 2017. After that, the bird laid 11 eggs. The bird then incubated eggs for 12 days. On the Easter Monday, the first shells cracked and newborns started poping out of the eggs.

Blok shema gnezdilnice z večino sestavnih delov. 

I prepared the whole project for local school. The nesting boxes were made by 8 children aged from 11 to 14 during afternoon classes. It was great fun and the young scientists learned many new skills from electronics, materials, hand tools, crafting, programming, components, circuit design, biology, photography, physics, etc… The nesting box is described in detail here with all necessary production steps. Contact for further info is m@v4.si. The three nesting boxes placed in the wild have…

live video feed and sensor readouts available H E R E.

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Raspberry Pi breakout board with ESD, PoE and Cortex M0

This is Raspberry Pi GPIO connector breakout board with some additional features:

  • “Real” or “passive” PoE with 12V output
  • 5V DC/DC module
  • Additional 3,3V regulator
  • ESD protection on all GPIO pins
  • two additional pins for each pin on R.Pi 40 pin GPIO connector
  • Separate UART and I2C headers
  • 3,3V Supply for periphery is selectable: from R.Pi or from external regulator
  • STM32F070 or similar in TSSOP-20 housing for controlling additional sensor or any other hardware
  • Jumper for Cortex-M0 / R.Pi UART connection

First prototype

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