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dropping voltage

Old 05-26-2003, 12:14 AM
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Vormulac
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Default dropping voltage

hey I was wondering if anyone in here knows how to drop voltage using a voltage dropping resistor? I need to go from 7.2v to 5.5 or 6v @900mah. if I have it figured correctly I'm looking at 7.5ohm resistor.. Any help????
Old 05-26-2003, 02:03 AM
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NitroHolmes
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Default dropping voltage

How did you get 7.5 Ohm?
Old 05-26-2003, 03:53 PM
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Vormulac
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Default dropping voltage

because of the voltage I need dropped... 7.2v minus 5.5v gives me 1.7v that needs dropped. If you take 1.7v and divide it by 900mah(the current needed) you get the resistance needed for the dropping resistor. that hurt my brain.
Old 05-26-2003, 05:58 PM
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NitroHolmes
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Default dropping voltage

Yeah, that's what I was thinking too, but here's what I got:

(1.7v) / (900mA) = (1.7v) / (0.900A) = 1.89ohms
Old 05-26-2003, 07:12 PM
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Vormulac
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Default dropping voltage

I got the same as you when I re-calculated. But I set up the circuit on electronics workbench and checked the voltage, I only got it down to 5.5v when I used a 7.5ohm resistor. It didn't match the math, but I haven't seen it be wrong yet.... but maybe I just did.
Old 05-26-2003, 10:38 PM
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NitroHolmes
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Default dropping voltage

What else is in your circuit? When you're running at 7.2V what is the resistance and current of the circuit?

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