News items for tag electronics - Koos van den Hout

2020-09-02 An update to the home 1-wire network
For more than 12 years now(!) the house has temperature sensors using the 1-wire protocol. I recently redid some of the wiring between floors and I finally got around to rerouting the 1-wire network via this new route.

I also added a temperature sensor in the big room in the attic, we are thinking of using that room more often. To get an idea of how good that idea is we wanted to get an idea of the temperatures up there and that's what I have 1-wire sensors for! I soldered an 18b20 sensor to the end of a 4-wire flat phone cable, added it to the network and it's measuring.

So now 12 environmental temperatures are measured every 5 minutes: 9 in the house, one in the weather hut, one in the shed and one on the roof of the shed.

I also updated the 1-wire projects overview with how I use 4-wire flat phone cable in RJ45 connectors for 1-wire network. I had to look up how I did that previously before I could start adding new cables!

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2020-07-03 The GPS ticks!
I remembered the junkbox contains an active GPS antenna which I bought together with the gpskit gps unit in 2003(!). And some other bits and pieces included a SMA to BNC adapter so I put the little GPS antenna outside and connected it to the GPS/RTC Hat.

Before I was back behind a computer it was showing a location and within a few minutes it had a PPS pulse. I was used to cold start taking at least 15 minutes with the gpskit!

So I tested with ntpd talking to gpsd via shared memory. This gave an interesting offset between local gps time and a nearby ntp server.
$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*SHM(2)          .PPS.            0 l    6   64  377    0.000   -0.149   1.672
xSHM(0)          .GPS.            0 l    5   64  377    0.000  -104.51   1.943
+ntpritchie.idef 131.211.8.244    3 u  101   64  376    2.774    0.950  13.948
+metronoom.dmz.c 131.211.8.252    2 u   99   64  376   10.482   -0.844  10.638
$ ntpdc -c kern
pll offset:           -0.000136461 s
pll frequency:        -11.054 ppm
maximum error:        1.3748e-05 s
estimated error:      1.7071e-05 s
status:               2001  pll nano
pll time constant:    6
precision:            1e-09 s
frequency tolerance:  500 ppm
I'm not too happy about the fact that the GPS NMEA messages are seen as wrong, so I'm going to stop using gpsd and go for a setup optimized for timing.

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2020-07-01 A new home timeserver: GPS/RTC board
The Raspberry Pi GPS/RTC Expansion Board from uputronics came in today (thanks mailman!).

Next part needed: a gps antenna. But that's on backorder with another supplier.

Also needed: time to install raspbian on the Pi and start testing.

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2020-06-29 Newish electronics project: an igate
Some time ago I saw announcements of an igate build project from PI4RAZ, the amateur radio club in Zoetermeer. An igate is a system that receives APRS messages and forwards them to the Internet aprs servers.

There is a distinct lack of APRS coverage here in Utrecht, so more places that receive those messages and pass them to the Internet are a good idea. A specialized repeater to repeat them on the air would be even better, but that needs a special radio license which is one step too far and expensive at the moment for me.

The electronics came in months ago, but time to pick up the soldering iron and start with the hard part wasn't available. I started this monday with that hard part: soldering a VHF module on top using something close to surface mounting. Just with a lot more space between the soldering islands than real surface mount. Still needed good light and a magnifying glass to check my work constantly. I only had to desolder one small blob of solder which went in the wrong direction.

After that I soldered the resistors. That went fine. After that my eyes were too tired, but the first step has been made.

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2020-06-15 A new home timeserver on order
After earlier tries to have a nice GPS-based timeserver for my home network I noticed a simple but very effective GPS 'hat' for the Raspberry Pi, the Raspberry Pi GPS Hat from Uputronix. While the Pi's are already taking over the home network just one more could be a nice addition. In the longer run this will probably replace the shed computer.

So I ordered a Pi with an added dual-band WiFi adapter, a case, the GPS hat and a GPS antenna. The GPS hat has PPS support so I will get the time correct. With the instructions from 5 minute guide to making a GPS Locked Stratum 1 NTP Server with a Raspberry Pi it should be easy. If this all works I may even add the resulting Pi to the IPv6 NTP Pool.

Update 2020-06-16: SOS Solutions came back with some bad news: the uputronix Pi GPS Hat isn't available anymore. I'm now looking at the comparable adafruit hardware which is somewhat more expensive, but offers the same options.

Update 2020-06-18: And the adafruit hardware is also not available soon. I cancelled the GPS unit part of the order and I'm looking at sourcing a GPS module for the Pi from another source. The GPS hat which sossolutions no longer sells is originally from uputronics where a newer version of the Raspberry Pi GPS/RTC Expansion Board is listed as available on the site. Based on a ublox chipset which allows me access to a lot of the GPS data.

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2020-04-13 Beeping -- --- .-. ... . loud enough (2)
Today I had time to work on the transistor switching to make the morse oscillator work. As I noticed before the Kent Morse practise oscillator kit is powered directly via the key which draws more current than the nanokeyer I built can handle.

So I had to calculate a transistor switch. That's something I learned a long time ago when I did electronics trade school from 1985 to 1989. In Dutch: MTS electronica. That knowledge had to be dug up again when I did the advanced radio amateur course but since I didn't have to use that knowledge it all sunk away.

But, google to the rescue and I found lots of examples, but the easiest one was at Transistor as a Switch - ElectronicsTutorials which explained exactly what I wanted. The next item was 'which transistor'. The default NPN transistor is the BC547B, but the theoretical current through the oscillator is a bit more than this transistor can handle. But a fellow amateur had a few BC337 transistors spare in his junkbox, so I could continue with this project.

Today I did the drawing and the calculations. I looked up the specifications for the BC337 in full saturation, at which time the Vbe is 1.2 Volt, Vce is 0.7 volt and Ibase is 1 milliAmpere. So I ended up with a resistor of 6800 Ohm at the input (which is (9 Volt - 1.2 Volt)/1 millAmpere rounded) and after building it on a breadboard it went beep with an input current of somewhat over 1.0 milliAmpere.

Update: Second test was with the nanokeyer, which first gave no sound, but that was due to me turning the volume down on the practise oscillator. Turning it back up fixed the problem, and I now have loud morse!

In the end this is giving me a good feeling. I had a kind of problem I haven't had to solve in ages so I had to relearn how to solve this, I found the solution method and was able to apply it in theory, practice followed the theory and it all worked as designed.

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2020-04-02 Beeping -- --- .-. ... . loud enough
Kent morse practise oscillator built
The Kent morse practise oscillator built
To practise my morse at the radioclub I looked for a simple morse practise oscillator and found Morse practise oscillator kit - Kent and ordered it at the beginning of Februari. It took a while for it to arrive, but it arrived and I built it in one evening.

It's a quite simple kit. Which means the power for the whole circuit runs via the morse key, in theory about 120 mA. And that is more than the octocoupler on the CW output of the nanokeyer I built is willing to deliver (50 mA). So I can't use the practise oscillator straight away, there will need to be a small amplifier in between.

Some searching suggests I can use a transistor as 'power amplifier'. Time to look at what I may have (which is not a lot) or find a transistor somewhere.

Solution: order a bunch of transistors in a collection so I have some in the junkbox.

Oh and: The dashes and dots in the title are the word 'MORSE' in morse.

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2020-03-09 Newer power supply not yet delivering what I want
I did some more testing with the HP power supply I bought last November. In previous tests the output voltage seemed to be limited at 13 volts and it seems limited to 13.10 volt at the moment. The RM Italy HLA300V plus amplifier I have will only output about 55 watts maximum in digital modes so that's less than I expect. A higher input voltage may fix this, but I'm not sure how to get the power supply to deliver this and keep running. The previous power supply gave up in a busy weekend but before that the HF linear amplifier delivered more power. I have seen it go over a 100 watt on digital modes. The difference in output from the linear amplifier with 13.10 or 13.27 volt power is quite large, which surprises me.

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2019-11-23 PC control of the TS-480 radio working again, including for remoterig
I dug into the "why isn't remote CAT control not working" on the Kenwood TS-480SAT with the remoterig setup and as the debugging session progressed I found out it wasn't even working locally. The Kenwood TS-480 radios have a male db9 connector just like the PC had, and the non-intuitive part is that it needs a straight-through cable with data lines and hardware flow control.

I had a bunch of serial cables and adapters cobbled together to get from DB9 female to DB9 female with wires 2 and 3 coming out uncrossed, but it did not have hardware flow control and that had worked one evening before but now it decided to go on strike.

Thanks to the visit to the "Dag van de radio amateur" (DvdRA) ham convention and the extra parts ordered on-line from Conrad I had enough parts to make my own serial cable with the right wiring, including covers for the connectors with the cable coming out on the side.

So my skills in building right serial cables using a soldering iron, flexible wire and an amount of patience were recalled. I am very sure I haven't done that yet this century. Old CAT-5E cables are a good source of flexible cable with 8 wires.

When I had a finished cable with hardware flow control I first did a local test before I started putting the covers on the connectors and when that did work fine I put the covers on, redid the test and switched to testing over the remoterig connection. That also worked.

Update: And for the laptop which doesn't have serial ports I activated the COM port to USB translation on the control side. It took a bit of searching before I found that /dev/ttyACM0 was the active port, so now I can run CQRLOG on the laptop with full control of the radio.

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2019-11-16 Getting distracted by weird noises and listening to data from car tires
I was tuning across the 70cm amateur band and heard lots of weird noises around 433.92 MHz. Which is logical: that's the ISM band (industrial, scientific and medical) so lots of unlicensed low-power signals there.

That triggered me to update rtl_433 and see what I could receive. The answer after some searching how to build a running version: a lot. Including tire pressure monitoring sensors (TPMS) on a nearby car:

time      : 2019-11-16 15:33:25
model     : Toyota       type      : TPMS          id        : fb8c8bf9
status    : 128          pressure_PSI: 38.500      temperature_C: 6.000
mic       : CRC
There is indeed a Toyota parked across the street. I see three different values for 'id' suggesting that three wheels are 'awake' and reporting tire pressure data about every two minutes. According to eavesdropping the wheels, a close look at TPMS signals the sensors should only activate when the car is going faster than 40 km/h or when a special LF signal is active.
Read the rest of Getting distracted by weird noises and listening to data from car tires

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