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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 700 460" width="700" height="460" role="img" aria-labelledby="t2 d2">
+<title id="t2">LED wiring with separate ground pins - recommended</title>
+<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>
+<text class="xs" x="83" y="76" text-anchor="middle">receiver.ino</text>
+
+<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>
+<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>
+<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>
+<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">220&#937;</text>
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+<text class="s" x="404" y="111" text-anchor="middle">RED pair</text>
+<text class="xs" x="404" y="126" text-anchor="middle">long leg faces this side</text>
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+<text class="s" x="404" y="227" text-anchor="middle">GREEN pair</text>
+<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>
+<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>
+<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>
+<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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