Recent content by FinnFlyer

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    Down-Home Vibrometer

    Correction: It does appear to matter when sampling starts. I get stable phase results (on the bench) when starting sampling at start of trigger pulse. Going to try it again on the engine and then prop... Finn
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    Down-Home Vibrometer

    Thanks trimtab. I think the light bulb finally came on: Sample two channels simultaneously: 1) trigger signal and 2) accelerometer signal. Then do FFT on both sample sets. Note the frequency "bin" with the highest accelerometer peak (should also be RPM/60) Read the phase from the trigger...
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    Down-Home Vibrometer

    Thanks. It briefly mentions the Phase Spectrum but I guess the question is: phase in relation to what? Intuitively, if RPM is varied slightly in relation to the sampling frequency won't that shift the phases drastically? Perhaps that's why initially adding a weight is done in order to get a...
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    Down-Home Vibrometer

    Can you elaborate on this? Dummy channel? Indexed how? How do you related the extracted phase data to the trigger point? Trying to fine-balance the engine w/o prop to simplify things. Changed my low-pass filter to 100Hz and amplify the ADXL335 x-axis signal 200 times. (the z-axis has twice...
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    Arduino/ strobe controller + engine monitor

    Haven't looked into thermistors but as far as I know they are not linear. In other words you'll have to have a calibration table or formula. Not impossible but seems simpler to me to use a sensor with a linear output (and possibly voltage offset). Then you just need to subtract the (known)...
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    Arduino/ strobe controller + engine monitor

    The AT MEGA certainly will give you enough inputs for anything you can think of. To keep it simple for pressure and temp measurements use sensors that output 0 to 5 volts (or output serial digital signal): Pressure: MPX5... series Lower temps: LM34 (F) or LM15 (C), TMP35/36/37 for example. To...
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    Who here has no need/intention to add ADS-B OUT?

    Normally 1/4 mile but getting closer day by day. Runway may start flooding next week ... Finn (Second flight this morning of N214FL RV-4 Mazda 13B Renesis (50 min flight). Too over-propped to develop full horsepower and too restrictive openings in/out of radiators (A/C evap cores) for proper...
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    Who here has no need/intention to add ADS-B OUT?

    9FL5 Perhaps TFF said it better than me. I'm cheap and didn't want to accuse others of being cheap and selfish :)
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    Who here has no need/intention to add ADS-B OUT?

    I installed it in both my RV-3B and RV-4. Partly because I want to be able to fly to Clearwater (in Tampa Mode C veil), partly for "the other guy's" sake. Even in my isolated area I find it useful for traffic avoidance. Taking off I saw (on my iFly Nexus pad) someone coming straight into my...
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    Down-Home Vibrometer

    Now getting a decent scope signal. Two peaks, one slightly bigger than the other. Adding big washers to periphery of spinner do not alter them significantly. Then I spent most of yesterday learning about FFT. Programmed an Arduino Nano for prop balancing. Meanwhile I then found that my Rigol...
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    So I though I would buy some books from the EAA.... silly me

    So I'm not the only one. Several months ago I tried ordering the experimental kit to get the decals, etc. Ended up ordering most of what I needed separately from ACS at a much lesser cost. A couple of days ago I tried ordering the flight test kit/cards. Same thing as original poster...
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    Looking for someone in or close by FL. who can fabricate engine mount.

    When I made my mount for my RV-3 and Mazda 13B, I made a copy of the firewall in plywood. Laid the plywood flat. Hung the engine from the prop shaft. Then started cutting and adding tubes and welding them. On the RV-4 with 13-B Renesis I supported the engine with concrete blocks and wood...
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    Down-Home Vibrometer

    OK, so not as simple as I thought it would be. 1. Three pulses per rotation or one pulse for every three rotations? 2. The o'scope has a FFT match function. but minimum resolution is 50Hz, so that probably won't work. I'm not familiar with the math behind FFT. A scope normally shows amplitude...
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    Down-Home Vibrometer

    Reflective alum tape on one bolt shank end, the other bolt ends and nuts black with a sharpie. I am getting an excellent signal from the one bolt. But overnight I realized why my filtering doesn't work. I have a 100K resistor from photo transistor to +5V. Then at the other end of the cable 47nF...
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    Down-Home Vibrometer

    No, I haven't, but that sort of makes sense, except the Rotary 13B is supposed to be smooth. So the trick appears to be to extract only the prop vibrations from the signal. Probably what trimtab is talking about (I still need to wrap my head around his post). Finn
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