Notes on power
From Steve Holton on the support-gang list, but good things to use when making your wiki resources for chargers...
==VOLTAGE== "VOLTS" The XO 'likes' around 12-14 volts, but should be able to charge (slowly and inefficiently) down to about 9V. DC-only and center pin positive. Both are critical. Make sure you check this for any re-tasked power supply you want to try. I would avoid a power supply offering more than 25 volts, or less than 9. But these are unlikey anyway. ==CURRENT== "Amps" The 'Amps" rating is a measure of how much current the supply will allow a device to pull before (essentially) blowing an internal fuse and killing the power adapter. You'll ideally want a supply that is comfortable supplying about 1.5 amps (which is pretty beefy) because then the XO will never ask for more than the power adapter can supply. The risk of using a power supply with a smaller 'Amps' rating is that the fuse will blow (in the power adapter) which will kill the power adapter. Any power supply with a greater-than-1.5 Amps rating will be fine, with the understanding that a) it will be unnecessarily more expensive, and b) there's a risk that whatever is drawing the power (the XO) will develop a fault and draw more than 1.5 amps, but less than the overcurrent protection of the power supply, and so the failsafe mechanism will fail to trip (a fancy way of saying the fuse won't blow.) ==POWER== "Watts" The other common rating of a power supply is the power, measured in Watts. This is usually a rating of how much (maximum) the power adapter will *consume* (so it's listed as an input parameter) and includes power lost to the AC/DC conversion process. The XO consumes 17 Watts of power at maximum draw. So if the power supply indicates it uses less than 17 W, it won't supply a full 17 W onward to the XO. (That's important for the alternative energy folk as well: if you're trying to find a solar panel, hand crank, wind turbine or perpetual motion machine to run an XO, make sure it can supply enough power to run a 15-20W lightbulb over a period of hours or you won't be matching the standard power needs of an XO. That's a LOT of cranking over a period of 2 hours. Hand crank flashlight/cell phone rechargers generally provide less than 5 volts and total power measured in milliwatts. These just won't cut it for powering the XO.) ====== I have found two viable alternative power supplies: The first the 19V 1.84A (roughly 80 watts consumed) power adapter from the Netpliance I-Opener mentioned above. The power plug is as close to an exact part match as I've been able to find. (But it's not green). The bad news; these are unsourcable parts. The other is a 12V DC, 500 mA (0.5 Amp) power supply with a close-fit plug. This unit: 1. is under-powered (only rated for 500mA vs. 1420mA for the OLPC Green supply) 2. gets hot when charging an XO. 3. has a loose-fit plug which occasionally needs 'wiggling'. 4. is NOT a lead-free device, so probably is not appropriate for children. The good news is that these will recharge an XO (a good workaround solution for someone who's only XO power supply has failed, leaving their XO otherwise unpowered) and are available in my area. ($10 gets you the 500mA power adapter, a 12V car adapter with the same plug, and a wind-up flashlight/weather radio to boot)
Mchua 09:28, 22 May 2008 (EDT)
So you're the infamous Chris! I've heard about you from Mel, and I think that I've spoken too everyone else at ilxo on irc or the phone except for yourself. Anyway. I was browsing the hardware articles you've been working on and I'm impressed. Good work. There is a pretty lively Flickr OLPC group that I manage, one of us should upload your photos as another method of distribution. Seth 21:05, 31 May 2008 (EDT)
Bridge Design Handout
Any chance of getting that bridge designer activity referenced in the lesson plan rewritten as an activity?
I went to the jhu site and played with it a little. It would seem to be a natural fit as an educational activity.
As a model railroader I also feel like pointing a couple of MR lists to it. Frequently there's the 'does this bridge make any sense' discussion.
Do you know what it is written in? Any encumbrances to using it? Or may the simplest solution be (ahem) reengineering it?
Rmyers 16:55, 8 June 2008 (EDT)
I like that idea, though I don't have a lot of time to put together a bridge building activity for the XO at the moment. I'll start doing some work on it toward the end of summer.
Power link dump Cjl 23:42, 8 June 2008 (EDT)
- Apcupsd is a UPS control system that permits orderly shutdown of your computer in the event of a power failure. Apcupsd source code is released under the GNU General Public License version 2
- Richard said this isn't viable -- deprioritize, in any case. --Andrea
- And the links to the report/presentation are dead.
IBM AC/DC combo power adapter
You might want to try to get your hands on a couple of "Lenovo AC/DC combo adapter 73P4503", this is the 72 watt version, I think there is also a 90 watt version. The tip works okay in the XO (maybe a little extra wiggle, but it works). The really cool part is that this can either plug into wall for AC source, or you can use the cigarette light adapter to plug into 12V DC source. Figure out what's inside one of these and you're well on your way. Cjl 17:38, 10 June 2008 (EDT)
Voltage_regulator is uncatagorized. But seems to be a work in progress. Could you categorize it please? 18.104.22.168 05:45, 2 July 2008 (UTC)