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Car Battery Charger from Spare Parts in Mint Tin

Step 2: Assemble and wire

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Use the two # 4 screws and nuts to fasten the heatsink and LM317 to the top of the box, with the LM317 leads to pass through to the inside of the box.

Cut the power jack from the notebook power supply. This is usually a round ( barrel) plug which plugs into notebook). Strip and tim the leads.

Usually, the center wire is positive, but use a voltmeter to ensure this is true

Strip and tim the wires which will connect the regulator box to the auto power plug. I used 10 feet of 16 guage lamp cord because it was handly. long is good, as it allows the electronics to be placed out of the weather.

Wire the box per the schematic. Make sure to not have either of the pairs of wires to touch the metal box. The metal box is already connected to one of the pins of the LM317. Repeat, DO NOT WIRE ANYTHING TO THE METAL BOX.

Use generous amounts of hot glue to fasten down the resistor, the wire leads, the leads of the LM317, and the points where the leads pass in and out of the box.

Plug in the notebook power supply, and measure the voltage on the auto power plug. This needs to be 13.7V or more for proper operation. In the below pic, it is 16.16V, a relatively optimal voltage.
 
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guerroloco5 years ago
If you're not supposed to wire anything to the box, how come your schematic shows a wire connecting negative to "case"? And, the picture shows two wires soldered to the box. This matches your schematic but not your written instructions.
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