Laser Rain Gauge – Status Report # 1
Project Members:
Dr. J. Young, Dr. R. Baraniuk, J. Halbouty, C. McPheeters, G. Picazo, E. Rodriguez, D. Wu
Summary:
This Laser Rain Gauge project is a continuation of a previous year’s project, The
Communication is the Illumination, whose goal was to build a cheap, reliable network of sensor
nodes that are capable of reliably and accurately measuring rain rates. From previous work, it
was verified that the received signal is indeed related to the rate of rainfall, however there is still
a number of issues that need to be addressed in order to accomplish our goal of independent
nodes forming a scalable weather network. Similar, if not identical, nodes will form the
backbone of the network. They will gather data and perform both analog and digital signal
processing via circuitry and a DSP chip before transmitting a signal to a base station. The
transmission will be accomplished by wireless means, such as radio or FSK laser transmission.
Any remaining processing of the signal will be done at the base station to result in a real time
signal representing the rain rate.
Goals:
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Develop an independent laser driver node that is capable of transmitting a given binary
signal using FSK. We might use a Gnome to control the transmitter, this will also give us
the possibility to use its radio capabilities to transmit data.
Design a new algorithm for interpreting the received RMS laser signal and interpreting
this into an actual rain rate instead of just giving us a “laser RMS space”. This algorithm
should be significantly simplified so as to be implementable on a DSP chip.
Develop an independent receiver node using our algorithm that does not require external
hardware for processing. This node should output a real-time rain rate signal, in order to
accomplish this we will need to unify the receiving and processing of the signal into the
same process.
Develop a method for finding the calibration constant using the new hardware.
Establish a method for transmitting the data, i.e. rain rate, back to a base station. This
might involve networking the nodes, or using radio transmission.
Progress:
We have implemented an independent laser driver circuit that outputs a 10KHz square wave or a
DC output. It has a power regulator circuit and can run off of a 5 – 20 volt battery.
We have also started working on an independent laser driver circuit that will implement FSK
transmission based on a voltage input.
We have a good understanding of how the previous group approached the problem. We have
gone over the Labview programs that were written last year and figured out what each one does,
and discussed which ones might actually be useful for the implementation of the “new”
algorithms that will be used on the DSP chip.
We have determined that the sampling rate of the received signal can be lowered, but we still
need to ensure that the Nyquist frequency of 2.2 KHz suffices for our purposes.
We have begun to test the DSP chip to find out what it can and can’t do, as well as reading on
some of the programming constraints (using c). Code for the DSP chip we plan to use can be
synthesized from LabView and Simulink schematics, so this will provide an efficient way to
develop software. At the time we are figuring out which algorithms/programs should be
implemented first so that we can start doing basic data analysis using the chip.
For next cycle:
1. Finish the FSK laser transmitter (Ed & Joe)
2. Get the DSP board to take in an analog signal, scale it (or some other elementary processing)
and output it on one of the board’s digital outputs in its native format. ( Clay, Picazo, & Dan)
3. Send the 10KHz square wave laser signal to the receiver and use the signal coming from the
receiver as the input for the DSP board and do the same processing as above. So we should be
able to digitize and scale the signal using the DSP board. (Everyone needs to get together for this
one)
3. Determine how to get a rain rate, not laser RMS data. (Ed & Joe)
Team Cycles:
#1.
#2.
#3.
#4.
#5.
30 August - 8 October: Ed
9 October - 19 November: Clay
20 November - 28 January: Joe
29 January - 18 March: Daniel
19 March - 29 April: Picazo