G'day Andrew, There is a voltage above which the XO-1 will not charge, which had been often encountered by people using solar panels. Along would come a cold sunny day, with a greater than normal voltage, and the charging would stop.
I don't recall the actual voltage (Richard may remember), but I think it was somewhere near 18V, and it varied slightly between laptops. So it might work, or might not. Instead of using a resistor, you might use two or three large diodes in series, each of which will provide a "forward voltage" 0.6V drop. Pick the diodes based on the maximum current 1.85A (usually double that), and the power that will be released as heat; P = V x I, where V is 0.6, and I is not to exceed 1.85A, so 1.11W minimum "power dissipation". Place them in a way that does not hold the heat in. https://learn.sparkfun.com/tutorials/diodes p.s. if you find one diode does what you need, then add another in case of variation in the supply or laptop. You might even add a full-wave bridge rectifier instead of two diodes, that way the input polarity won't matter. On Wed, Dec 11, 2013 at 01:52:54PM +0000, NoiseEHC wrote: > Hi! > > I am thinking about using my laptop's charger instead of the OLPC > charger in the future as I move a lot and it's getting really > tiresome to bring both chargers with me. The plan is to create a > converter plug and use only the laptop's but it has different > voltage levels. > > laptop: TOSHIBA > part: PA3715U-1ACA > model: PA-1750-24 > output: 19V - 3.95A > > XO-1.75: DARFON > model: BBOJ-C > output: 13.5V - 1.85A > > So can I plug my XO to the TOSHIBA adapter? The page says that > 11-18V needed, while the laptop's is 19V. Shall I use a resistor to > drop the voltage or is it unnecessary? Power usage is not an issue > to me. (BTW I will use the plug from the XO-1's charger, I guess > that it did not change in the meantime.) > > Thanks, > Andrew > _______________________________________________ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel -- James Cameron http://quozl.linux.org.au/ _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel