BETS1 BEAM Engine Test Stand 1 -- Mycroft2152, April 2003 Building & Using BETS1 BETS 1 Test Results Test results I've settled on running 5 tests, each having 5 SE "pops". This gives an average of 25 "pops," which should even out any bumps. Also it is convenient for logging the values -- I generally run 2 sets of 25 "pops." Just to get my feet wet, I ran a couple of trials. For these, I've created two metrics: distance per "pop" and distance per uF. The first trial I conducted was of a stock FRED (I already had in my box) with varying capacitors; 2200, 4400, 6600, 8800 uF. Distance (inches) per "pop" of a FRED SE, as a function of storage capacitor size (click to enlarge) Distance (inches) per uF of a FRED SE, as a function of storage capacitor size (click to enlarge) I found that on the FRED tests, it appears that there is a non linear relationship in distance travelled to capacitor size. By increasing the capacitance by a factor of 4, you get an 8 fold increase in distance, and almost double the distance per uF (octane?). The second set of trials I conducted compared FRED vs. 1381 SEs using identical capacitors and solar cells. Distance (inches) per "pop" of two SEs, FRED vs. 1381 (click to enlarge) Distance (inches) per uF of two SEs, FRED vs. 1381 (click to enlarge) It was interesting to watch the cursor move across the screen. I noticed that the cursor did not move the same distance each time. This was confirmed when I did the calculations. So, I set up a 555 timer with a 5 volt regulated supply to pulse the motor (a Solarbotics pager from the solar racer) and ran tests on it. Interestingly enough the distance traveled was very nearly consistant [each within about 5% of the average -- ed.]. Distance (inches) per "pop" of a 555-based circuit (click to enlarge) Since the 555 can be considered to output pulses at a fairly constant frequency, this means that the BETS1 is measuring SE behavior to within about 5%. Not shabby for something you can build from a spare computer mouse! Building & Using BETS1 BETS 1 Test Results

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