EmilyJane:
Now, the question is, how does one compute the direction of the vane pointer? The weather station reports 1 of 16 unique positions.
You'll need to define one of the 'positions' as North - obviously this is installation dependent. The rest is basic trigonometry. Determining current position and direction of travel is most likely similar to handling rotary encoders.
Graynomad:
First question, why have 8 if they are spaced at 45 degrees, surely that means 4 of them are redundant?
Rob
I don't understand why you say 4 are redundant. How would you get 16 unique directions with only four switches? I see that 24 = 16 but I don't see that that helps.
Graynomad:
switch (reading)
0x12:
// north
0x23:
// north west
I was thinking that with the HE sensors at 45 degrees they are effectively operating in pairs as you would always have both opposites on at the same time.
Would that not be the case?
I can see that if the magnet actuates adjacent pairs when it's in the centre that would double the resolution, but I still can't see the point in having sensors directly opposite each other.
"reading" is the value read from the IO port that these sensors are on. In this case PORTC, so
byte reading;
reading = PINC;
switch (reading)
0x12:
// north
0x23:
// north west
So, if I number the HEs 0-7 like in the attached drawing and they are wired to PC0-PC7 for purposes of this discussion and the top of the drawing is North. Let's also assume that an activated HE has a value of "1", regardless of how we would accomplish that.
Then if the rotor is pointing North, what would be the value of "reading"? If the rotor was pointing South, what would it be?
The original Dallas 1-wire instrument used a DS2450 4 input A/D converter with 8 reed switches and rotating magnets to determine direction. Someone wrote a sketch to read the speed and direction with an Arduino. I am using it as part of my weather station. Find it here...
billcramer07:
The original Dallas 1-wire instrument used a DS2450 4 input A/D converter with 8 reed switches and rotating magnets to determine direction. Someone wrote a sketch to read the speed and direction with an Arduino. I am using it as part of my weather station. Find it here...
Maybe the new AAG instrument is using a similar method.
Your link didn't work for me. I believe the original 1-wire instrument switched resistors with its reed switches so as to get unique A/D readings for each direction. This one doesn't appear to be switching any resistors.
I believe the original 1-wire instrument switched resistors with its reed switches so as to get unique A/D readings for each direction.
That would make a difference. Still I think removing a magnet would be easier. Maybe add a similar weight to keep the balance.
Rob
Very good. That's exactly what those inscrutable Chinese did. That gray thing that looks exactly like the other one is a dummy. Only one is a magnet.
I'm proud to say I figured it out before I actually verified it. Like Sherlock Holmes said, whenever you've exhausted all the possibilities, whatever is left, no matter how improbable, is the answer.
The remaining mystery to me is why they went to such trouble to hide what they are doing. The dummy looks EXACTLY like the real magnet. It's like they had a big batch of defective ceramic magnets to use up. The rotor that operates the HE for wind speed does have two functional magnets and looks identical to the Wind direction rotor. Curiouser and curiouser.
I'm still left with the problem of reprograming the stock chip. Anyone with any suggestions about that please step in.
from Pololu or someone (there are a few around) and make up a 6-way to 5-way cable.
Rob
I might end up doing that but there's no reason why I can't use an Arduino for this project unless the manufacturer has burned the fuses to disable reprogramming.
EmilyJane:
The remaining mystery to me is why they went to such trouble to hide what they are doing. The dummy looks EXACTLY like the real magnet. It's like they had a big batch of defective ceramic magnets to use up. The rotor that operates the HE for wind speed does have two functional magnets and looks identical to the Wind direction rotor. Curiouser and curiouser.
Unlikely that they're hiding anything. Perhaps a counterweight? Provided for balance?
EmilyJane:
I'm still left with the problem of reprograming the stock chip. Anyone with any suggestions about that please step in.
Adafruit sells a little ISP programmer (usbtiny) that should do the job nicely. It's supported directly by avrdude.
BTW, the Bus Pirate that I mentioned yesterday also fulfills this purpose. Also supported by avrdude. Just sayin'...
Oh, and my earlier suggestion regarding position is based upon experience with my own AAG weather station. You really don't get a useful position until it moves.
EmilyJane:
The remaining mystery to me is why they went to such trouble to hide what they are doing. The dummy looks EXACTLY like the real magnet. It's like they had a big batch of defective ceramic magnets to use up. The rotor that operates the HE for wind speed does have two functional magnets and looks identical to the Wind direction rotor. Curiouser and curiouser.
Unlikely that they're hiding anything. Perhaps a counterweight? Provided for balance?
EmilyJane:
I'm still left with the problem of reprograming the stock chip. Anyone with any suggestions about that please step in.
Adafruit sells a little ISP programmer (usbtiny) that should do the job nicely. It's supported directly by avrdude.
BTW, the Bus Pirate that I mentioned yesterday also fulfills this purpose. Also supported by avrdude. Just sayin'...
Oh, and my earlier suggestion regarding position is based upon experience with my own AAG weather station. You really don't get a useful position until it moves.
EmilyJane:
The remaining mystery to me is why they went to such trouble to hide what they are doing. The dummy looks EXACTLY like the real magnet. It's like they had a big batch of defective ceramic magnets to use up. The rotor that operates the HE for wind speed does have two functional magnets and looks identical to the Wind direction rotor. Curiouser and curiouser.
Unlikely that they're hiding anything. Perhaps a counterweight? Provided for balance?
EmilyJane:
I'm still left with the problem of reprograming the stock chip. Anyone with any suggestions about that please step in.
Adafruit sells a little ISP programmer (usbtiny) that should do the job nicely. It's supported directly by avrdude.
BTW, the Bus Pirate that I mentioned yesterday also fulfills this purpose. Also supported by avrdude. Just sayin'...
Oh, and my earlier suggestion regarding position is based upon experience with my own AAG weather station. You really don't get a useful position until it moves.
I'm sure it's a counterweight as you suggest but it is made out of the same material that the magnet is made from. Maybe they are readily available from another process/product.
I finally got avrdude/ArduinoISP to talk to the WS but I'll probably order one of the Adafruit programmers to use in the future. The problem was I needed to over-ride the baud rate in avrdude. Coding Badly figured that one out.
The new AAG will be even easier to determine wind direction now that I realize that there is only one magnet. It will work when the vane is stopped as well.
I decided to go ahead and bump the clock frequency up to 16 MHz so as soon as a crystal arrives, I'll get back on this project. I'll be using a USBtinyisp and a USB/TTL serial interface instead of an Arduino for programming and communication also, so everything should go smoothly.