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08-05-2009, 09:27 AM #1
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zxn474l
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current/9 volt battery and diodes

What is the total aproximate current from a typical 9volt battery? In a parrallel ciruit using just one 9 volt battery and powering three diodes all in parralell with each other would the total current from the 9 volt battery be divided by 3 and each diode recieve a 1/3 of the current from the battery at 9 volts which is well under the max ma for any one diode?

08-05-2009, 09:39 AM #2
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ThunderBird89
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Re: current/9 volt battery and diodes

There's no such thing as 'current for a 9V battery'. Current is voltage divided by resistance, so you need the resistance of the circuit, or at least one diode to calculate the current.

08-05-2009, 12:36 PM #3
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Re: current/9 volt battery and diodes

Also, i have my doubts about each diode recieving 1/3 of the total output without some sort of current regulation. I believe that more current will simply flow to the diode(s) which offer the least internal resistance, or basically the most effecient of the bunch.
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08-05-2009, 01:43 PM #4
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ThunderBird89
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Re: current/9 volt battery and diodes

That's the least of his problem, I think, but true: you always need some sort of active current regulator. Depending on the forward bias of the diode and the budget, I'd say a RckStar driver, with its output split threeways would do the thing, no? Although the input power would probably have to be raised to three 9V batteries, but at least it's massively durable, and hard to damage short of catastrophic overvolt.

Or if you want to go safe, and you have the money, you could order three FlexDrives, which are buck-boost drivers, so they will always keep the current and voltage at the proper setting, but are easy to overload and short out. However, with pulldown resistors and a lot of calculation, you should be able to split a 9V input into three, each of which is palatable for a FlexDrive

08-05-2009, 06:04 PM #5
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HIMNL9
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Re: current/9 volt battery and diodes

probably he means the maximum current that a 9V-type battery can give ..... old types, zinc-carbon, was something like 50 / 100 mA, the alkaline ones can give like 200 / 300 mA or few more (don't really think much more) for a short period of time.
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08-05-2009, 06:34 PM #6
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ThunderBird89
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Re: current/9 volt battery and diodes

So not really much, especially if it has to power three diodes. Still, he should use some sort of current regulator, just to keep those diodes safe. I certainly wouldn't power them up with just a limiting resistor in series with each...

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