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Originally Posted by Draven Ah, that is a good idea. Sorry for such a rudimentary question, but would the resistor be inserted on the positive or negative end of the LED-wired-in-series array (for lack of a better name)? Oh, and at the 0.875 volts cutoff point, how long do you think it would take for the batteries to be damaged to the point of no longer functioning, if there were about 1 charge/discharge per day with that mechanism...

I'll do a little searching, but one thing that comes to mind is to use an off-the-shelf 12VDC to 120VAC inverter (common, cheap, UL approved), and a 120VAC-to-24VAC transformer (also common, cheap, UL approved). If we don't find a good pre-existing inverter to 24VAC, then this might be a good alternative. Especially if you can come up with some use for 120VAC in the system as well...

You can always put a series resistor from +24 volts to the collector, so that the IR voltage drop is ~15 volts (R = 15/0.12 = 125 ohms, I 2 R = 1.8 watts), and reducing the transistor power loss correspondingly. Bob S

Is polystyrene a good insulator for electric field? I gues its just a thermal insulator...Any way i gonna try it. Is there a way to detect a change in peak to peak voltage and obtain this change as high or low output?? For example, to detect such a change as in attachment ( 80mV change)

Oh, excellent! I'm gonna ask another newbie question (but I promise I don't ask questions twice ); what kind of resistor should be used (for example, a 2.2k)?

It's funny that you bring this up after this thread was resurrected recently. http://www.physicsforums.com/showthread.php?t=197240

Originally Posted by berkeman Don't think you can solder to stainless steel. You should probably be reading about how to weld to stainless steel instead. Sure you can, but you need to use special flux made for soldering stainless steel (I quite often have to solder SMA connectors to stainless steel coax). You don't need any special equipment or special solder, but you DO need to flux in order to make a good joint (it IS possible to...

Originally Posted by Draven I see. Is amperage proportional to voltage with solar cells? Is it possible to find one, or create an array of several wired in series, that are ~4.4 volts but at the same time ~250mA? Wired in series increases the voltage, wired in parallel increases the current. So if you have 4.4V cells that are 18mA each you would need 250/18 = 15 of them in parralel to give 250mA. That's the problem with these garden...

if you could make up a schematic of the XOR circuit that is a frequency double that would be helpful. i'm not really electrically inclined. i know ohms law and watts law and resistance, voltage and amps but that's my extent of electrical knowledge.

Ok,thank you everyone for the valuable advices and suggestions. I will look into it in my next lab session.