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Step 6Home, Home, has no range
One of the first things we noticed, was that the range died a horrible death as soon as we walked out of the office with the transmitter. We tried from a different room, and the results were terrible. 1 feet away it crapped out. Time to look at solutions.
It occurred to me that where we testing we had 4 sources of Wi Fi within 5 feet, all in the 2.5 Ghz range like the Xbee. Also we did not "aim the Xbee at all. After researching I determine I could buy a more powerfull Xbee radio (about $23) or add antennas.
One of the things I needed was a good Range test. The X-CTU software from Digi has a "Range Test" built in, but it did notthing. I spent some time tryin gto figure out how to make it work. Actually this was as easier done than said. I did not really need the X-CTU test, just the "RX Signal Strength Indicator" (RSSI) value.
I looked in the xbee.py Tweet-A-Watt uses and right there, line 39: [code]self.rssi = p[3][/code]
Which means it is part of the Xbee return value! (xb.rssi in wattcher), so I modified a debug line for my hack:
print str(counter) +": RSSI: " + str(xb.rssi) + " | " + time.strftime("%Y %m %d, %H:%M")+ ", " + ": Voltage: " + str(CalcualtedVolts) + " avgv " + str(avgv) + " Thermistor: " + str(x) + " Temperature: " + str(Temperature)
Which produces a line like this:
373: RSSI: 82 | 2009 04 26, 11:18, : Voltage: 1.80100585938 avgv 593 Thermistor: 71.2276559865 Temperature: 78.6813444881
You can also see RSSI with processing, from Tom's Igoe's page. Though you will want to modify the packet length (at the top), as Processing complained about writing past the end of the packet buffer size. I believe you must be greater than 2 * expected packet length. Tom's code looks backwards for a previous packet which means if it misses the Ox7E packet indicator, it could run for while. Given that I am near the outer edge of measuring range, it can happen for a while. I set mine to 600 and it stopped giving me the "error, disabling serialEvent()" message.
Tom's code merely prints the latest setting, which is not all that useful for me. My debug line let's me track changes as Minion #1 wonder around.
Now we had a good way to measure, more than "hey dad we have a packet" it was time to try some home brew antenna ideas!
Using ideas from http://www.usbwifi.orconhosting.net.nz/ I have found that the Corner Cube measured a decrease in dB, though in practice did not seem to help connect a disconnected pair. The Vegatible Steamer actually was the best at aiming and reconnecting. USB Wifi's setup is much different from some other folks. The steamers have a stem in the middle which makes for easy XBee placement. A pho bowl with tin foil also see promising (though we just removed the tin foil later and held it in place). We also tried making a parabola with a bending piece of hot wheels "track," but it did not seem to help.
One of the problems is that we were testing at the outer edge of the range. Most 2.5Ghz radio, XBee especially, use spread Spectrum which means they can take a but to "sync" and then the XBee software looks for the beginning of an XBee packet before trigger. This means if you get an all or nothing effect. Either the radios lock onto each other, or not. Sometime it seems like luck, but in fact you are an antenna at these ranges and can be impacting the results.
I went to buy two steamers but then found that the cost of a steamer from the local supermarket was $10, and for the price of 2 steamers, I can get a more powerful XBee. So I looked at a few more places and found a pretty deep strainer which has turned out even better. It was $7. I believe the deepness is important , since I am on the transmitting end of things, it reflects more of the signal (per the notes in http://www.usbwifi.orconhosting.net.nz/number13.jpg).
End results, is that with a vegetable steamer on one end (to be replaced) and a strainer on the other, I have signal about 20-30m, from an interior office, through 3-4 walls, out to the hot tub!
Pro tip: Remember to bring the strainer in if you want 1) Your spouse to stay, and/or 2) Want steamed vegetables later.
Personally I like the petal-like appearance of the vegetable steamer.
It occurred to me that where we testing we had 4 sources of Wi Fi within 5 feet, all in the 2.5 Ghz range like the Xbee. Also we did not "aim the Xbee at all. After researching I determine I could buy a more powerfull Xbee radio (about $23) or add antennas.
One of the things I needed was a good Range test. The X-CTU software from Digi has a "Range Test" built in, but it did notthing. I spent some time tryin gto figure out how to make it work. Actually this was as easier done than said. I did not really need the X-CTU test, just the "RX Signal Strength Indicator" (RSSI) value.
I looked in the xbee.py Tweet-A-Watt uses and right there, line 39: [code]self.rssi = p[3][/code]
Which means it is part of the Xbee return value! (xb.rssi in wattcher), so I modified a debug line for my hack:
print str(counter) +": RSSI: " + str(xb.rssi) + " | " + time.strftime("%Y %m %d, %H:%M")+ ", " + ": Voltage: " + str(CalcualtedVolts) + " avgv " + str(avgv) + " Thermistor: " + str(x) + " Temperature: " + str(Temperature)
Which produces a line like this:
373: RSSI: 82 | 2009 04 26, 11:18, : Voltage: 1.80100585938 avgv 593 Thermistor: 71.2276559865 Temperature: 78.6813444881
You can also see RSSI with processing, from Tom's Igoe's page. Though you will want to modify the packet length (at the top), as Processing complained about writing past the end of the packet buffer size. I believe you must be greater than 2 * expected packet length. Tom's code looks backwards for a previous packet which means if it misses the Ox7E packet indicator, it could run for while. Given that I am near the outer edge of measuring range, it can happen for a while. I set mine to 600 and it stopped giving me the "error, disabling serialEvent()" message.
Tom's code merely prints the latest setting, which is not all that useful for me. My debug line let's me track changes as Minion #1 wonder around.
Now we had a good way to measure, more than "hey dad we have a packet" it was time to try some home brew antenna ideas!
Using ideas from http://www.usbwifi.orconhosting.net.nz/ I have found that the Corner Cube measured a decrease in dB, though in practice did not seem to help connect a disconnected pair. The Vegatible Steamer actually was the best at aiming and reconnecting. USB Wifi's setup is much different from some other folks. The steamers have a stem in the middle which makes for easy XBee placement. A pho bowl with tin foil also see promising (though we just removed the tin foil later and held it in place). We also tried making a parabola with a bending piece of hot wheels "track," but it did not seem to help.
One of the problems is that we were testing at the outer edge of the range. Most 2.5Ghz radio, XBee especially, use spread Spectrum which means they can take a but to "sync" and then the XBee software looks for the beginning of an XBee packet before trigger. This means if you get an all or nothing effect. Either the radios lock onto each other, or not. Sometime it seems like luck, but in fact you are an antenna at these ranges and can be impacting the results.
I went to buy two steamers but then found that the cost of a steamer from the local supermarket was $10, and for the price of 2 steamers, I can get a more powerful XBee. So I looked at a few more places and found a pretty deep strainer which has turned out even better. It was $7. I believe the deepness is important , since I am on the transmitting end of things, it reflects more of the signal (per the notes in http://www.usbwifi.orconhosting.net.nz/number13.jpg).
End results, is that with a vegetable steamer on one end (to be replaced) and a strainer on the other, I have signal about 20-30m, from an interior office, through 3-4 walls, out to the hot tub!
Pro tip: Remember to bring the strainer in if you want 1) Your spouse to stay, and/or 2) Want steamed vegetables later.
Personally I like the petal-like appearance of the vegetable steamer.
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