Mare & Gal Electronics

Here is scenario:

pushbutton is connected to Raspberry Pi GPIO pin. Whet button is pressed, R.pi calls remote URL.

This can be useful for many simple applications, like detecting and timestamping passes at certain location.

The R.pi should be up and running. Connect the pushbutton to free GPIO. In our example we connected the button to pin 11. The pin is configured with the pullup, which means the button must pull the GPIO pin to ground. Pin 12 on r.Pi model 2B (40 pin P1) is GND:

Ultra simple schematic for this example

Now prepare some simple script on your fancy web browser, which will be called when someone presses the button. Here is example, which simply adds one line with time and date at the end of the file “log.txt” every time when file is loaded:

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This is 5 minutes soldering project. There is no schematic, just simple circuit, something between “dead bug” and conventional PCB design. I did this in two steps. First attempt was complete failure. Local OM told me that any power mosfet can operate as power amplifier for HF. Ok, maybe not just any. I tested with couple of them including IRFZ24N. Finaly I took “proper”  MOSFET for higher frequency and the circuit worked pretty good:

Simple output stage for QRSS beacon assembled in “mixed” technology

I will briefly describe this quick and simple project and I hope readers would enjoy it.

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Once finished (deadline is end of January) this project will become open-source software and hardware.

My quadruple BDC driver for supports up to 4 brushed motors with encoders. Each motor is controlled by its individual closed loop and individual PID gain settings. Additionally, motor speed can also be individually addressed. Analog part of the driver is based on DRV8701P predriver and is controlled by STM32F4 microcontroller.

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Ina soldered today 16 leds in matrix and then we connected it to “LED Decoration” hardware. The basic idea was:

4×4 LED matrix Xmas tree

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This LED decoration is for beginners in microcontroller applications. It has 8 LEDs, audio generator and possibility to interconnect with other modules. The PCB is simplified to certain level in order to be manufacturable on a single sided substrate with minimum effort. There are only two wire bridges and one 0 ohm resistor in addition to other components. The LED decoration can be used in school projects or for new-years fun. Of course it’s not limited to X-mas tree. It can be used during Bodhi Day, Hanukkah, Id al-Adha, Winter Solstice celebration, Saturnalia, Yule, Kwanza, Omisoka or any other occasion which might come at the end of the year, when day is short and some LED blinking device might rise your mood.

The concept of this LED decoration:

LED decoration concept

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I recently received 1m of APA102C led strip with 144 leds per meter. I want to use the strip for rotary POV display so I cut the strip in half and tested the performance with a STM32L476RGT nucleo board. The results of the tests are surprising and very promising for my application.

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There will be series of simple(r) circuits for my new electronic course for elementary school. For start we need power source. Batteries are fine until flattened out, therefore it’s good to have rechargeable one. I took MCP73831T-2ACI/OT, added micro USB connector and switch to select between charge/discharge mode. In the charge mode, the output is connected to +5V input supply. The power is delivered to the charger via micro USB connector, which means eny mobile phone USB supply will do the job. The charge current is limited to 2A and battery cell has integrated protection circuit. I will add 3D printed housing for the complete pack after the testing of first prototypes.

Prototype of the battery pack

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Our home vineyard delivers about 1000 liters of wine every year. It takes some effort to keep good quality and pleasure for all friends tasting the must, new wine and “senior” wine reserves. One of the most important tasks in wine quality management is controlling the biological and chemical state of the wine. The wine can be monitored in special laboratory or in home lab. Of course home lab become rational when quantity of the wine is high enough to justify expenses in special equipment.  There is some low cost equipment available for wine analysis, mostly with titration techniques, but chemical lab equipment is rather expensive and many hobby wineries avoid buying such equipment. I hope this post can contribute a bit to change that. I will describe the development of simple pH meter in detail.

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Penny skateboards are available on every corner for something under 20€. They are a lot of fun to ride on and are very useful when someone has to travel a great distance in pedestrian only area. But what happens when a 2.5 kW electric motor is attached on it? Scroll down to find out.

Finished electric penny board

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