Fail: Adventures in ultrasound anemometers

I want a little weather station for the flat. Something with Temperature, Humidity, Rain amount, and of course Wind speed and direction. Normally you’d use a cup anemometer. There are severals other variants, i.e. one measuring the run-time of an ultrasound wave travelling along a known line in the wind. That’s quite interesting…

You can buy these SRF04 ultrasound range finders for less than 5€. I removed the mask-rom µC and connected one of these cheap arduino-clones to the outputs.

Der Arduino erzeugt also die 44kHz für die Ultraschallsensoren (für ein paar µs) und wartet dann 100ms bis der Zyklus wieder von vorn beginnt. Die Windgeschwindigkeit ergibt sich dann aus der Differenz der Laufzeit zwischen vor- und rücklaufendem Signal und der Schallgeschwindigkeit (sowie Temperatur etc.).
Die Transducer habe ich in 3D-Gedruckten (PETG) Haltern in einer Küchenpapier-Rolle montiert, zusätzlich befindet sich an einem Ende ein kleiner (5V) Lüfter:
Detail der Lüfter-Montierung:


Hier das empfangene Signal direkt aus dem Vorverstärker (CH2, Cyan), getriggert auf der ersten Flanke des TX-Signals:

Sieht vielverstpärechend aus. Setzt man jetzt einen Cursor an eine Flanke des Signals bei 0m/s Wind…

lightbox…und den anderen bei 240% Wind (5V Lüfter betrieben mit 12(!)V)…

lightbox…so zeigt sich dass zwischen 0 Wind und #Orkan 5,4µs liegen (zumindest auf der Länge einer Küchenpapierrolle). Die Windgeschwindigkeit im Versuchsaufbau war durchaus nicht zu unterschätzen und dürfte tatsächlich durchaus Orkanstärke erreicht haben.

Mit dem weiterhin verbundenen Aufwand (IO-Mux, Vorverstärker etc. etc.) macht es nicht wirklich Sinn, das zu vertiefen. Es gibt noch eine Variante mit stehenden Ultraschallwellen; vielleicht baue ich sowas mal… 😉

Wouxun KG-818 VHF Teardown

On the Hamradio Friedrichshafen I got myself a Wouxun KG-818 VHF (5W, 136-174.995 MHz). I plan to realize a small APRS transmitter for my car.

“The Wouxun…”

…whithout batteries. You have to remove the screws on the bottom left and right…

…as well as the nut around the antenna connector …

…to slide-wedge the whole assembly bottomwards-out. The dials will come off as well as some plastic thingy. Beware of the ribbon!

The two modules. On the left the processor/TRX-board, on the right, the LCD/speaker/kexs section with part of the case.

And once again the TRX/Chinagirl-module. Unfortunately the PCB is soldered to the RF-connector, which prevented me from further teardown, because I had no soldering iron at hand. Underneath the firmwaresticker it reads “M64X802”.

Great!” The TRX works even without its keys/speaker etc attached!

Well and that’s about it. I will mod this further so stay tuned.

eZ430-Chronos unboxing

This was in my mail today…

It’s from Digi-Key! Let’s crack this sucker open…

Ok, I’ll see what I can do… 😉

Look!!! I found an eZ430-Chronos! 🙂

The Chronos was on sale on tiDeals for $25 or so, so I bought one…

Little extra: The CHronos RF modem and a MSP-eZ430U Debugger (epic win!!)

As Dave would say: “Don’t turn it on, take it apart” (actually with the supplied screwdriver..), this is what you cet; the Chronos watch module (with debugging connector).

Unfortunately the Chronos is a little ugly (even more than on the website – so I think I won’t wear it.. 🙁 ). Also it consistently measures the altitude 500m too high (haven’t found barometer setup yet). But it sure is a great toy and the MSP-eZ430U Debugger/Programmer is worth it’s money.

So.. Stay tuned!

Magmount refurbishment

I do (of course) have an antenna on my car, which was to date mounted with a pretty rusty old magmount. I don’t know; our local marten didn’t like that at all, the RG-58 which was unprotected ~20cm was completely torn to peices.

To cut it short; I didn’t document the process. I could only reuse the magnet from the original magmount, the connector was completely encased in PVC and thus irretrievable. So i turned a new connector holder out of delrin (POM) and milled the fitting for the connector with my CNC. After I de-rusted the magnet, drilled matching holes, applied a base coat and some layers of laquer I screwed on the holder with V4A INOX screws.

Tada…. (click for larger..)


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