After a LOT of investigation of the La Crosse TX20, I’ve managed to fully decode the complete datagram from the La Crosse TX20 INCLUDING the Checksum.
The La Crosse TX20
Here’s everything you’ll ever want to know about the pin out and the communications protocol of the La Crosse TX20.
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I’ve been wanting to build a weather station, complete with the Geiger counter I’ve been working on. Building the wind speed and direction sensor seemed like a daunting task, especially since they need to be weather tight, but have moving components in them.
Since it’s nearly impossible to acquire an AAG or Dallas 1-wire Anemometer I decided to purchase a TX20 Wind Anemometer and use an AVR to decode the interface from it and reformat to a protocol more suitable for me.
The La Crosse TX20
I’ve managed to find some very useful information on a Violet Ray design through the Google Patents website. The patent number is 1506344. The link to the patent is http://www.google.com/patents?q=1506344. This patent isn’t for the model I’m trying to repair, but it gives some very useful information.
This includes a basic electrical circuit and theory of operation.
It also confirms my suspicions that the yellow cylinder covering the primary coil is likely to be the capacitor (Condenser). I suspected it as this yellow component didn’t appear to contain a winding coil and appears to be permanently connected in series with the primary coil to the AC power in.
I'm pretty confident the yellow part is a condenser.
I hope to test the individual components this weekend and should be able to deduce what’s wrong with it.
With the lower cover removed, it becomes clear that the internals of this Violet wand are very similar to the Master brand unit. This should make it a lot easier to find problems than blind investigation.
The intensity knob is mechanically linked to an electrode which contacts with an armature. I believe the armature oscillates electromagnetically due to making and breaking the circuit as the primary coil is energized.
A closer look at the primary coil and switching components
I believe the big outer yellow cylinder may be a capacitor, but not 100% sure as of yet.
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The first step to any repair is getting into the guts of the device…. primarily without damaging it.
There is very little information on the web about the internals of these devices. It looks very similar to the Violet Wand made by the Master company, so I got hold of some diagrams from patents and took it from there.
All of the information on the internals I could find, was available at http://www.electrotherapymuseum.com/Articles/VioletRayConstruction.htm
The wand could be unscrewed in the middle, but the parts couldn’t be separated. Something was stopping it from coming apart.
The Violet Wand has two small indents near the intensity adjuster.
The two small indentations
I was hoping that there were screws in “dem dere indents”. I carefully scraped at the indents and found that they were in fact some sort of wax.
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I’ve been asked to take a look at a non-functioning Violet Wand in the hope that I can repair it back to working order.
The Violet Wand I've been asked to repair
These devices have many uses from being used as Quack Medical devices, through to being used in bondage and other extreme activities – The ones used for the extreme activities are typically higher powered devices though. And anyway, who am I to question, when I’ve been asked to take a look at something that uses high voltages and resonant transformer circuits (Tesla anyone?).
The first step will be trying to get the device open without damaging it.
Stay Tuned…
I can happily say our move into our new house went well, and even though we moved only days after the shortest day of the year, the weather was (mostly) favourable and we moved almost everything over the weekend with only a couple of small boxes left to move tonight.
I managed to manufacture the steel frames for the Hen House last week and assembled them directly off the machine, mainly to test the machine, but it’s also faster than flat packing then assembling later.
The steel frames at home and ready to be turned into the Hen House
I’m about to move to a two acre lifestyle property in South Auckland and plan to build a Hen House to keep hens and ultimately, get fresh eggs.
Since I work in the light gauge steel framing industry, it was a no brainer that the Hen house (Chicken Coop) should be made out of steel and engineered for the local climate.
I decided on the size of 1800 x 3600 mm (6 feet x 12 feet). I chose this size for two main reasons. 1: I was going to clad it with plywood and plywood comes in 1200 x 2400 (4 feet x 8 feet) sheets and 2: It was well under the local council size limit of 10 square metres meaning I didn’t need a permit to build it.
I designed the hen house in the proprietary software developed by the company I work for. I decided that I would make two thirds of the space for the hens and one third for storage of chicken supplies (and in the future, my supplies for beekeeping).
My Hen House design rendered in 3D
I managed to find out some information on the СБМ20 Geiger Müller Tube.
I tracked down the following image on Google Image Search…
With the help of a Russian speaking coworker, I was able to find out the most important specs for this tube.
Nominal working current: 400 volts
Minimum plateau length: 100 volts
Maximum plateau slope: 0.1% per volt (10% per 100 volts)
Working range (min): 0.004 mkR/s
Working range (max): 40 mkR/s
Minimum life: 2*10^10 pulses
Hopefully this will help someone else.
I managed to get the Geiger counter kitset working.
I believe it was a problem with the high voltage leaking through some flux. Either way, a good cleanup around my solder joints seemed to fix the problem.
The Geiger Müller tube is a is a Russian model, marked with the code СБМ20 – There are lots of results on google for searches for “CBM20″, but very little of use regarding the actual specs of the tube.
I’ve been trying to measure the voltage across the Geiger Müller tube. It turns out that with no capacitor regulating the high voltage, the 10MΩ internal resistance of my multimeter and oscilloscope is enough to drop the voltage significantly. The normal way to get a reading is to add 90MΩ in series with the meter. This effectively creates a 10:1 voltage divider while increasing the total resistance of the measuring circuit to 100MΩ.
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