Charger HOWTO This document describes the proper way to assemble your battery charger. Address questions to 6.270-tech@mit.edu. All parts can be obtained from the 6.270 office. Each kit should have an AC adaptor in it already. Other components can be obtained from the 6.270 office. Parts (1) Jameco AC adaptor (1) 1.25" x 3" printed circuit board (1) RS401L rectifier (2) SPDT slider switches (2) Yageo 5 Watt 7.5 Ohm wire-wound resistors (big white blocks) (2) 5 Watt 15 Ohm metal-oxide resistors (2) green LEDs (2) red LEDs (1) 1 kOhm resistor pack (2) female battery connectors Note: due to a shortage of parts, the charger kits only contain ONE female battery connector. Additionally, the pins on the connector are spaced slightly too far apart to fit into the board. Just take a pair of pliers and bend them slightly to make them fit. Tools Soldering iron Instructions This is your board: The first step is to solder the battery connectors to the board. Orient the board as in the picture above, with the word "component" facing you in the lower-left corner of the board. The first thing to do is to solder the battery connectors to the board. Once you do this, the board should look as below. When you plug your battery pack into the board, the positive lead (red wire) should be to the right. Next solder the resistor pack and LEDs in place. Orient the resistor pack so the pin marked with the square goes into the hole with the square pad in that line of eight holes. Next, put in the LEDs. Red ones are marked with an 'R', green with a 'G'. One of the sides of the LED is slightly flattened, that side should be towards the right. When oriented like this, the short lead of the LED should be in the hole with the square lead. When you're done, your board should look like this: Next solder the power resistors in place. It doesn't matter which way you put them in, but leave about 1/8 inch of space between the big rectangular resistors and the board so they can dissipate heat more effectively. After this, solder the slide switches into the sets of three holes to the left of the big resistors. These also don't care which way they get soldered to the board. When you're done, your board should look something like this: Next, solder in the rectifier. The angled corner should be to the left. The last step is to hook up the AC adaptor. Cut the end off the wire that comes out of the big transformer block, separate the wires down a few inches, and strip about 3/4 inch of insulation off the ends of the individual wires. Solder the two wires to the remaining two holes in the board. It doesn't matter which wire goes in which hole. When you're done, the board should look like: You should be all set to charge your batteries now. The slider switch controls the speed your batteries will charge at. To the left is "slow", it'll take 8-12 hours to put a full charge on your batteries; to the right is "fast" it'll take 2-4 hours to put a full charge on your batteries. Don't leave your batteries on fast-charge overnight. When charging in fast mode the red LED should turn on, when in slow mode, the green LED should turn on. However, if your batteries are below about 4.5 V the LEDs will not operate until the batteries have charged some. When the batteries have a full charge they will feel warm on the charger. Always check the voltage on your batteries after charging. If it's above 7 V you should discharge them some with a resistor before plugging them into the board. Come find an organizer if you need help. Be careful not to set your charger on anything conductive when it's plugged in, as the pins on the back may short out. As a corollary to this, unplug your charger when you're not using it to charge your batteries.