Right now I’m assembling a first prototype of the detector node. I’ve determined a few things which need to get done in order to make sure the device will work how I’d like it to.
1. Optimize timing accuracy
I’d first like to see how I can modify the GPS settings to get the most accurate clock pulses. I also want to experiment to find the best algorithm for utilizing the GPS pulses. This means measuring how many Arduino clock pulses it takes for a single GPS pulse over time, and seeing if averaging is necessary. This also means making more intelligent code which accommodates for the timer ticking while each byte is recorded. (I haven't thought through that last part entirely, but I may not have to accommodate for this delay as long as it is consistent.)
2. Optimize protocol for server communication
I need to find a balance between minimal processing by the Arduino and minimal transmission size. I also need to determine if the detector node should immediately send data, or rather accumulate data on the SD card and then send it to the server.
3. Increase detector sensitivity
I realize now that a single pin diode probably isn’t enough. This means I need an array of pin diodes. I need to determine which pin diode on the market is most worth its cost. I also need to determine which amplification circuits and ICs work the best.
4. Determine calibration procedure
All nodes need to have the same sensitivity and delay; this means calibration is important. I need to determine where in the circuit pots or adjustable caps are required, and what accuracy each discreet component needs to be. Then, I need to find a good way to ensure that the nodes can be calibrated without any expensive test equipment. One idea I have is to use readily available americium from smoke detectors to calibrate sensitivity.