Leeenux - Linux distribution for eee netbooks

Disclaimer

This circuit is intended for people who have had experience in constructing electronic projects before. The circuit design and build process are provided simply as a reference for other people to use and I take no responsibility for how they are used. If you proceed with building and/or using this design you do so entirely at your own risk.

Parts List

• 2x 10k resistor (R1 & R4)
• 2x 22k resistor (R2 & R3)
• 1x 1.5k resistor (R5)
• 1x 120μF 25v electrolytic capacitor (C1)
• 1x 2200μF 16v electrolytic capacitor (C2)
• 1x 1N5822 Schottky diode (or equivalent)
• 1x 9.1v 0.5W Zener diode
• 1x BC337 NPN transistor
• 1x LM2576T-ADJ IC
• 1x 100uH, 3A inductor (e.g. Pulse PE92108KNL)
• 25°C/W or better minature heatsink (e.g. Thermalloy 6073)
• Cigarette lighter plug with 3A fuse and 2.1mm DC plug (e.g. DSE P1692)
• 2.1mm DC chassis mount socket
• 1.7mm x 4.75mm (ID x OD) DC plug and cable
• Small plastic enclosure

Building It

Make yourself a PCB using the template below (600dpi). I simply laser print (or photocopy) the design onto OHP transparency sheet and then transfer the toner onto a blank PCB using a standard clothes iron. Any missing spots can be touched up with a permanent marker before etching. This is quick, usually results in pretty tidy boards and hardly costs a thing.

Install the components on the PCB and triple check the layout before soldering. It is much easier to start with the low profile components such as resistors and diodes, then install the larger components afterwards. Don’t forget the wire link; this is shows as a red line on the layout guide above.

Remember to smear a small amount of heatsink compound on the regulator tab before mounting the heatsink.

For a case I used a small plastic enclosure from DSE, part H2840, as it was all the local store had in stock that was remotely suitable. The PCB is designed to fit into this particular case, however any small box should be suitable. If you have a dead laptop charger lying about it might be worth ripping the guts out of that and salvaging the case. If your enclosure is different you may need to modify the design to suit, so I have provided the schematic and PCB design files for download. They were created using Eagle.

The Eee uses a standard 1.7mm DC power connector with a positive tip.

Testing

Connect the circuit to a 12v supply. If you use a car or lead acid battery ensure you have a 3A fuse fitted in line with the circuit before connecting it, just in case.

Use your multimeter to check that the circuit outputs about 9.45v with no load. Connect a 12V, 21W lamp (e.g. old brake lamp from a car) or similar load across the output and check that the voltage doesn’t vary much.

You should now be able to connect your Eee. The circuit design should be good for up to 2.5A, so there is plenty of margin for the Eee to fully function and charge its own battery off this supply.

Thanks to http://www.marlwifi.org.nz/projects/asus-eee-car-charger for information