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  • Harvesting Sound Energy From Passing Cars

    The rectifying bridge drops your voltage by two diode drops; you might do better with Schottky diodes (lower Vfwd).However, the big question is how much power is developed. You could try inserting a current meter + a resistor across the cap, but I suspect it will be very hard to measure because both the voltage and current are quite low. A better approach would be to put various size resistors across the capacitor, while measuring the voltage on the capacitor - these will simulate voltagae and power when carrying a load. Suppose you measure 0.2v sustained with a 100Kohm resistor; that would indicate that it generates 2uA of current at that load, or 0.4 uW. Or suppose that it shows 0.1v with a 10K resistor - that would be 10uA and 1uW. Suppose you could get 0.15v with a 1K resistor...

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    The rectifying bridge drops your voltage by two diode drops; you might do better with Schottky diodes (lower Vfwd).However, the big question is how much power is developed. You could try inserting a current meter + a resistor across the cap, but I suspect it will be very hard to measure because both the voltage and current are quite low. A better approach would be to put various size resistors across the capacitor, while measuring the voltage on the capacitor - these will simulate voltagae and power when carrying a load. Suppose you measure 0.2v sustained with a 100Kohm resistor; that would indicate that it generates 2uA of current at that load, or 0.4 uW. Or suppose that it shows 0.1v with a 10K resistor - that would be 10uA and 1uW. Suppose you could get 0.15v with a 1K resistor (unlikely), that would be 150uA and 23uW.The forward drop of most diodes are not specified at such low currents, so I don't know if a Schottky bridge would help or not, but you might try it.I wonder if it's helpful to have a tuned mechanical resonator, when your sound looks more like white or pink noise, so you are extracting only a thin frequency slice of the broad spectrum sound energy. The small peaks in the FFT can be meaningless noise (noise as in signal to noise ratio, not as in sound) that disapear if you average many samples, or due to one set of tires passing at a given time, not to be repeated often.And finally, piezo elements can produce much higher voltages; I wonder if you have managed a very efficient coupling between your mechanical oscillators and the piezo element. You want as much as possible of the mechanical vibrations to be damped/absorbed by the piezo. Try another mounting approach.Thanks for the thought provoking instructable.

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  • Make the Harbor Freight 45W Solar Panel Charge Controller useful with a simple mod.

    This is kind of old, but just in case others are finding it, I'll offer some notes.1) Do not put blocking diodes on the battery - the whole point is that this system stores energy into the battery as well as taking it out again, so that flow needs to be two way.2) Blocking diodes on the solar panel MIGHT make sense, to avoid draining the battery into the panel at night. However, some solar panels include an internal diode, and some controllers include an internal diode, so adding another one might or might not be needed for that purpose (I don't have the unit and cannot check).3) The blocking diode reduces the voltage from the solar panel, and thus the charging power available, so adding one if not needed is actually a bad idea. If you do use a diode, make sure it has enough current r...

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    This is kind of old, but just in case others are finding it, I'll offer some notes.1) Do not put blocking diodes on the battery - the whole point is that this system stores energy into the battery as well as taking it out again, so that flow needs to be two way.2) Blocking diodes on the solar panel MIGHT make sense, to avoid draining the battery into the panel at night. However, some solar panels include an internal diode, and some controllers include an internal diode, so adding another one might or might not be needed for that purpose (I don't have the unit and cannot check).3) The blocking diode reduces the voltage from the solar panel, and thus the charging power available, so adding one if not needed is actually a bad idea. If you do use a diode, make sure it has enough current rating (and that it's placed so it's OK to get hot). A Schottky diode has less voltage drop than a standard diode. One diode with a sufficient rating is somewhat preferable to two under-rated diodes in parallel (because the two may not divide the current evenly). Since OP says he got better results with a blocking diode on the solar side, then for at least his unit it may have been needed.

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