jessikitty
e1c5d00972
Four wires, no shared return junction, so the series-LED failure mode cannot occur.
57 lines
4.1 KiB
XML
57 lines
4.1 KiB
XML
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<title id="t2">LED wiring with separate ground pins - recommended</title>
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<desc id="d2">Board B GPIO25 goes through a 220 ohm resistor to the red LED pair and returns to its own GND pin. Board B GPIO26 goes through a 100 ohm resistor to the green LED pair and returns to a different GND pin. Four wires total and the two circuits never touch each other, so neither can end up in series with the other.</desc>
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<text class="h" x="83" y="59" text-anchor="middle">BOARD B</text>
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<text class="xs" x="83" y="76" text-anchor="middle">receiver.ino</text>
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<rect class="box r" x="36" y="100" width="94" height="26" rx="4"/><text class="s" x="83" y="118" text-anchor="middle">GPIO 25</text>
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<rect class="box n" x="36" y="150" width="94" height="26" rx="4"/><text class="s" x="83" y="168" text-anchor="middle">GND (a)</text>
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<rect class="box g" x="36" y="216" width="94" height="26" rx="4"/><text class="s" x="83" y="234" text-anchor="middle">GPIO 26</text>
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<rect class="box n" x="36" y="266" width="94" height="26" rx="4"/><text class="s" x="83" y="284" text-anchor="middle">GND (b)</text>
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<rect class="box r" x="182" y="100" width="86" height="26" rx="4"/><text class="s" x="225" y="118" text-anchor="middle">220Ω</text>
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<rect class="box r" x="320" y="94" width="168" height="38" rx="6"/>
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<text class="s" x="404" y="111" text-anchor="middle">RED pair</text>
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<text class="xs" x="404" y="126" text-anchor="middle">long leg faces this side</text>
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<rect class="box g" x="182" y="216" width="86" height="26" rx="4"/><text class="s" x="225" y="234" text-anchor="middle">100Ω</text>
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<rect class="box g" x="320" y="210" width="168" height="38" rx="6"/>
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<text class="s" x="404" y="227" text-anchor="middle">GREEN pair</text>
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<text class="xs" x="404" y="242" text-anchor="middle">long leg faces this side</text>
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<text class="s" x="404" y="318" text-anchor="middle">Four wires. The two loops never touch each other anywhere.</text>
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<text class="h" x="42" y="373">Why this version cannot fail the same way</text>
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<text class="s" x="42" y="395">There is no shared junction to get wrong. Each LED has one path out and one path back, so</text>
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<text class="s" x="42" y="413">neither can end up in series with the other. GND (a) and GND (b) are different physical pins</text>
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<text class="s" x="42" y="431">but the same net inside the board - that is fine, and it is what makes this safe to do.</text>
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</svg>
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