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#41
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"kony" wrote in message
... On Sun, 23 May 2004 12:18:59 -0700, ric wrote: kony wrote: So, if I used an array of LEDs to power a solar cell, I could get infinite free energy? Sure. Free except for the initial and replacement costs of the LEDS. (They aren't very efficient operating in reverse. Kinda like a microphone used as a speaker.) Huh? No free energy, it'd be a quite lossy. Shine a light in a LED, and you *DO* get a voltage out! Yes, free energy (minus the cost of the LEDs, as mentioned.) Yes, very inefficient, but they *DO* put out a voltage. Note that no mention was made as to how many LEDs would be needed to provide useful power. We seem to be interpreting the question differently... I read it to mean, powered LEDs, their light shining on a solar cell to generate electricity from the solar cell. That was how it was written. |
#42
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"Andy Foster" wrote in message ... "kony" wrote in message ... On Sun, 23 May 2004 12:18:59 -0700, ric wrote: kony wrote: So, if I used an array of LEDs to power a solar cell, I could get infinite free energy? Sure. Free except for the initial and replacement costs of the LEDS. (They aren't very efficient operating in reverse. Kinda like a microphone used as a speaker.) Huh? No free energy, it'd be a quite lossy. Shine a light in a LED, and you *DO* get a voltage out! Yes, free energy (minus the cost of the LEDs, as mentioned.) Yes, very inefficient, but they *DO* put out a voltage. Note that no mention was made as to how many LEDs would be needed to provide useful power. I think you would need a useful number of LED's. We seem to be interpreting the question differently... I read it to mean, powered LEDs, their light shining on a solar cell to generate electricity from the solar cell. That was how it was written. |
#43
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"Raymond Sirois" wrote in message news On Fri, 21 May 2004 22:47:30 -0700, ric wrote: Raymond Sirois wrote: LEDs draw an insignificant amount of current. LEDs, being diodes, draw *NO* current. They are connected *in series* with a impedance limited voltage, and pass - in one direction - the current that the series impedance dictates. There IS a VERY small voltage drop across a diode, as a result, there is a small amount of impedance. The power supply will see this as a load and therefore there will be current applied to the diode... never speak in absolutes. As I said, LEDs draw an INSIGNIFICANT amount of current... You are wrong. They draw a lot of current, thats why a series resistor is needed to stop them blowing. Raymond Sirois SysOp: The Lost Chord BBS 607-733-5745 telnet://thelostchord.dns2go.com:6000 |
#44
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kony wrote:
Shine a light in a LED, and you *DO* get a voltage out! Yes, free energy (minus the cost of the LEDs, as mentioned.) Yes, very inefficient, but they *DO* put out a voltage. Note that no mention was made as to how many LEDs would be needed to provide useful power. We seem to be interpreting the question differently... I read it to mean, powered LEDs, their light shining on a solar cell to generate electricity from the solar cell. Yeah, I guess so. Obviously powered LEDs need to pass enough current to provide light. But like a diode, they pass whatever current is provided to them, not draw current on their own. They'd likely not provide enough light to power a solar cell in any regard. I once powered a small LCD clock with a series/parallel array of LEDs. Worked great! But it was quite a bummer to reset the clock every morning after I turned on the shop's lights. |
#45
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ChrisJ9876 wrote:
My first thought was that the OP doesn't know the difference between voltage & current, and therefore shouldn't be messing with a multimeter. LOL, I do know the difference, I'm just not very handy with a multimeter. |
#46
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Trent© wrote:
On Fri, 21 May 2004 04:37:14 GMT, Cyde Weys wrote: I blew the fuse on my Radio Shack multimeter recently. I was testing the current across a 9V battery. I verified that it is just the fuse that was blown by removing the fuse, shorting across the gap, and verifying that the needle on the meter did indeed move on resistance tests (no way am I gonna test anything other than ohms without a fuse, hehehe). Anyway, my multimeter has the following options on it: 15, 150, 1000 DCV, RX 1K(Ohms), OFF, 150mA DC, 1000, 150, 15 ACV. I believe I left the battery attached to the leads when switching modes (is this bad?). I did not go into any of the ACV modes. So, can someone tell me how, with a 9V battery, I managed to blow a 315mA, 250V fuse? Thanks. If yer shorting the resistance-test circuit...and then the meter is moving...then you blew the resistance fuse. If you blew the resistance fuse, that means you had it in resistance mode when you checked the battery. Having the meter in ohm mode when checking the battery current will blow the fuse every time. I think you'll find that the meter has 2 fuses inside. Nope, there's only one fuse in there. I just checked. Unless one of the fuses is designed to be inaccessible and is squirrelled away in the back of the unit (wouldn't make a lot of sense). |
#47
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Let me try and explain this whole LED thing, and the fuse blowing
though it might be to late for this thread. The amount of current that is 'drawn' by the LED depends on the LED and the battery. Formula is this: A=V/R Where A is Current, V is Voltage, and R is resistance of the LED/multimeter. So a 9 V battery with a LED (typically around 1-10 ohms) will yeild a significant amount of current, ~1000 to 9000 mA. So to prevent this a resister is placed in the circuit to drop the current. This is also why the multimeter blew the fuse. on a DC Amp setting the resistance will be small, mine is rated at 25 Ohm. So the current will be more than the fuse could handle. Some multimeters have higher ranges, which just means there is more resistors in the circuit, and in turn a different range displayed. I hope this helped, I have a problem of my own... My dad, for reasons I don't know, tried to measure the current on a live 220V circuit and blew the multimeter without even blowing the fuse. I'm trying to trace the component that blew and need to find some schematics of a multimeter, any will do, just to help figure out what some parts do. if anyone has attempted to fix something like this let me know. Thanks ============== Posted through www.HowToFixComputers.com/bb - free access to hardware troubleshooting newsgroups. |
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