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Aug
25
Written by:
Gary Holbrook
8/25/2008 4:39 PM
This evening, having just gotten my hands on another USB to TTL\serial adapter, there was but one logical thing to do...revisit my XBee experiments.
My initial trial with XBee was mixed. I got the devices working, but they were incredibly unreliable from only a few inches away. That was shockingly short of the expected one mile range.
This time I decided that measuring transmission distance in inches simply wouldn't do, upped the ante. The following photograph shows the extreme communication distance that I attempted from my secret laboratory. Please note that the modules are separated by feet!
Sadly, my results were the same. That's unfortunate, because I had blamed poor board design on my part for the failure. Not so. Transmission was slow, and characters dropped for no apparent reason. The setup would be unusable for true data communications.
Reflecting upon my previous experience with the incredibly power hungry XBee Pro boards, I realized that the 9V battery attached to one of them might be part of the problem. While the voltage was high, current certainly was not. After retrieving a cage and four AA batteries from my other secret laboratory, I tried again.
Presto! The setup worked beautifully. Not a single dropped character, no delays nor pauses. While I have now had two problems due to the power consumption of the XBee Pro modules, I have still not looked up how much power they consume. Instead I'm going to continue speculating.
My near term goal is to use an XBee module on a remote controlled airplane. It will transmit data from the aircraft to the ground...I hope*. Given my recent experience with the XBee's ravenous appetite for power, it may be necessary to build an airplane large enough to carry a car battery.
*I recently purchased the radio for my airplane, and it also operates in the 2.4 Ghz range. It's a Futaba FASST system, so perhaps I'll be saved by the frequency hopping. It is altogether possible that I will not be able to run the two devices on the same aircraft.
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