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59 lines
1.3 KiB
59 lines
1.3 KiB
The example resistors in the adjustable section are R1 always 3K
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and R2, varies. You can double R1 and double R2 and get the
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same output voltage.
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So I will use an R1 of 6.8K
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with a base resistor, and an adjustable of
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base
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(would be for 13.5-13.8 according to powerstream sla page) volts)
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so let's do the math
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for 13.65 float voltage.
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6k( /(13.65/1.23) - 1 )
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13.65 / 1.23 - 1 == 10.09756
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6k / 10.09756 == 594.31
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There is a 590 resistor in e24 or something. Let's do that.
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That is base.
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For lowest voltage of 1.2volts (single nicad charged by sun)
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though nicads probably have memory issues, but they are cheap
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so who cares... (I think nimh might be better?)
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1.2 = 1.23( 6k/??? + 1)
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So solve for R2 which is unknown
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However my earlier math is wrong, since I need a 5900 resistor
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13.65 / 1.23 - 1 == 10.09756
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5900 / 10.09756 == 584.29
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So still a 590 resistor... Close as we can get. Well,
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there is a 583 on my chart, so
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5900
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583
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Base is 583, 5900 is R1
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Now what is the adjustable.
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Solve for R2, and remember you need the difference
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And can't go below reference...
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R2 == 5900 / (1.3/1.23 - 1)
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1.3/1.23 - 1 == 0.0569
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5900 / 0.0569 == 103690
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Quite a difference. We need to jump from 100K to 583.
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So I would add a 100K and that should get me close to 1.4 volts.
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Hopefully close enough. Done.
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