News items for tag electronics - Koos van den Hout

2021-05-03 Refreshing rechargeable batteries 2 months ago
With lots of devices running on rechargeable batteries including toys with motors and lights we have accumulated quite a number of rechargeable batteries in our house. Some of them have been around for ages and others are more recent.

With the amount of batteries varying per device (we have seen 1,2,3,4 and 6 batteries per device) it's good to charge each battery individually as they may have different residual charges and always charging them in pairs when one is not as good will only make the difference worse.

But the charger for individual AA/AAA cells we have also wants to charge the batteries quite fast and will abort as soon as one cell doesn't accept the charge. More and more batteries got rejected this way, even relatively new ones.

The solution: a smart charger that has adjustable load current, can refresh a battery that has problems accepting charge and measures the charge in the battery. And does this for 4 batteries at the same time. I gathered batteries from all kinds of places (quite a collection) and started charging and measuring all of them. A number of batteries got rejected because even a "refresh charge" ended at less than 50% of the original capacity. Those batteries will be handled as chemical waste. The others with enough capacity left are now all in the big box of charged batteries. Most of them will not keep their charge until the moment we actually need them, but it's good to know they are usable.

I bought the https://www.conrad.nl/p/voltcraft-ipc-3-batterijlader-li-ion-nicd-nimh-10440-14500-16340-16650-17355-17500-17670-18490-18500-18650-1403321 from Conrad which has only one downside: the fan is somewhat noisy.

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2021-04-07 The NTP ham clock is ticking 3 months ago
esp32 based NTP ham clock on breadboard Recently the parts for the NTP ham clock I saw in the Electron magazine arrived: an ESP32 module and a TFT display. It took a bit before I had time to actually do something with them but recently I put the modules on breadboard and started making the needed connections. There are not a lot of those, only 8 wires need to be connected between the ESP32 microcontroller and the TFT display.

After some fiddling it worked and I managed to program it all with the settings I like, such as the right timezone rules for the Netherlands, 24 hour display on both clocks and it fetches the NTP time from the NTP server in the shed so it doesn't rely on outside connectivity.

Now to find a case for it and wire it neatly.

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2021-02-27 Ordered parts for an NTP ham clock 4 months ago
Today the Electron magazine of the Veron amateur radio club came in, the March 2021 Veron Electron (Dutch).

As I was browsing the magazine and reading articles I came across an article about building an NTP ham clock, consisting of an ESP32 module and a TFT LCD display, and the rest is all in software.

I directly wanted to build this, as this combines two of my interests: amateur radio and NTP time synchronization. It displays both the local time and the UTC time on the TFT display, just like PyHamClock does on my screen.

The article is based on the same project at W8BH projects which gives me a good descriptive pdf.

So I ordered an ESP32 module and ILI9341 TFT LCD display from an aliexpress seller and now I wait, because this will take about a month.

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2021-01-05 Sharing my christmas light code 6 months ago
I forked the github repository GitHub - jgarff/rpi_ws281x: Userspace Raspberry Pi PWM library for WS281X LEDs into my own GitHub - KHoos/rpi_ws281x: Userspace Raspberry Pi PWM library for WS281X LEDs and committed my code for using the 120 led ledstrip as christmas tree lights including morse code.

It's my first actual python code.

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2020-12-31 The igate is still receiving packets and slowly building coverage 6 months ago
Coverage map of PE4KH-10 igate around Utrecht Since the igate build was finished and the first packets were received I left it running. I did switch to a 5 volt power supply: it works fine on a USB charger powering the whole circuit board via the USB connector for the ESP32.

Packets are received from a large area around the city as shown. I'm glad it is all working and I hope to improve the APRS network coverage here locally a bit.

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2020-12-23 A bluetooth speaker that is also a serial port 7 months ago
I acquired a Blaupunkt BLP6100 Bluetooth speaker. Which turns out to support the following services via bluetooth:
  • Headset (audio for phone calls)
  • Handsfree operation (use buttons to accept, hangup or reject calls)
  • Audio sink (the main function of a bluetooth speaker)
  • Serial port
That last one I did not expect. I have tried opening the port with minicom and it will say carrier detect but sofar trying to wake it at 115200 or 9600 hasn't resulted in anything.

As a linux audio device it works fine. Or as a bluetooth speaker for my phone so I can listen to podcasts while walking around at home.

But the serial port makes me wonder!

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2020-12-05 Playing with a fully programmable LED strip 7 months ago
At work there is a sort-of competition for the best christmas decorations in the office. At the end of last year I considered doing something with programmable LEDs to 'participate' in this competition in 2020.

This year turned out somewhat different, but slowly my son is also somewhat interested in electronics, soldering and making the computer do something.

So I set out to find fully programmable LED strips. I found a good comparison of LED strips in a Youtube video: LED Strips, what's the difference? WS2811, WS2812B, 2812Eco, WS2813, WS2815, SK6812, SK9822. which compares the several available types and their pros and cons. After viewing this video and for my limited experiment I thought the WS2812B based LED strip would be the best choice. The next hurdle was controlling it and I found Connect and Control WS2812 RGB LED Strips via Raspberry Pi which has pointers to the right code.

I am not following the advice on that page about working with mains power cables. That looks dangerous.

I ordered a WS2812B based LED strip and a matching power supply for 5V 40Watt from a Dutch webshop and got it in a few days later. I was amused by the warning the webshop gave that a LED strip like this is for advanced users only because you have to add a controlling device and do all the programming. That is exactly what I intended to do!

Programming is in Python3, and I haven't written any Python code before. But with a lot of google searches and looking at samples I got the idea right.

I now have the LED strip blinking in exactly the patterns I want, including a nice pattern for a christmas tree. And it blinks 'MERRY CHRISTMAS' in morse code, because why not!

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2020-11-08 RF knowledge helps fix completely different problems 8 months ago
For work I currently spent quite a bit of time in video conferences. I have an external webcam from work which gives a better image than the built-in webcam, but it regularly started giving problems in the image. Hickups or blinking images, suggesting some communications problem between the webcam and the computer.

Since the webcam, a Microsoft lifecam studio, is still being sold and advertised as works good with Windows 10 I thought it wasn't the age of the webcam or a problem with the drivers.

So I tried a different solution which is almost the standard solution of a radio amateur for interference problem: add more ferrite to the cables. The USB cable is thin which suggests to me there is not a lot of room for good shielding. Pulling the USB cable through a ferrite core twice right after the USB plug made the problems go away.

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2020-10-10 The igate is igating 9 months ago
pi4raz igate running showing packet
pi4raz igate running showing packet
I dug into 'how to build code for the ESP32' and found Installing ESP32 Add-on in Arduino IDE (Windows, MacOS X, Linux) and since I have the Arduino IDE working enough for the previous project with a programmable microcontroller: the nanoKeyer morse keyer I did the steps to add ESP32 support.

I had to find the right settings for the specific ESP32 chip and since it is labeled "ESP-WROOM-32" I ended up at ESP-WROOM-32: Uploading a program with Arduino IDE and used the settings 'Board: FireBeetle-ESP32', 'Flash Frequency: 80 MHz', 'Upload Speed: 921600'.

The sourcefile to compile and upload to the ESP32 in the pi4raz igate is pa2rdk/APRS_IGate/APRS_IGate.ino.

I changed the definition of struct StoreStruct for a bigger wifi password (64 chars) and noticed that after uploading the updated code the last parts of the StoreStruct got mangled. I changed to #define EEPROM_SIZE 174 which seems to fix this.

I will admit to doing a bit of cargo-culting here: just following some google results and fiddling a bit until it works, with limited idea what I'm actually doing and what the effect of my changes is. The kind of weird results I got after growing the wifi password buffer suggested clearly to me that I was looking at some sort of buffer overflow, so I started looking for buffer sizes.

But the igate is now talking to the APRS network. First results visible at PE4KH-10 tracked on aprs.fi.

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2020-10-06 Finished and tested the electronics of another project: the igate 9 months ago
After finishing the Raspberry Pi ntp server in the weekend I continued on a long-running project: the PI4RAZ igate I started working on in June (and ordered in September 2019). I dragged the soldering iron, the soldering mat and lots of parts downstairs to work on it on Sunday evening. Soldering lots of pins to an Arduino nano is hard work.

I finished the last soldering on Monday evening and had a long and hard look at all the connections and redid a few. I used a multimeter to make sure three really close soldering islands weren't connected, found two with 0 ohms between them in both polarities so I fixed that issue.

After that I took the plunge of actually powering up the print and it looks good. The display shows output and I can walk through the setup when I connect a usb cable to the ESP32 module.

I can't make it run yet: the space for the wifi password in the ESP32 module is only 25 characters which is not enough for our home network. So I will have to look into changing the code (it has an update anyway: Software update iGate - PI4RAZ) and find a working way to program an ESP32 from linux.

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