I thought to cross-over a discussion about needed power adapters for the XO-1 Laptop.<br>-iain<br><br><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Steve Holton</b> <<a href="mailto:sph0lt0n@gmail.com">sph0lt0n@gmail.com</a>><br>
Date: Thu, May 22, 2008 at 5:38 AM<br>Subject: Re: [support-gang] Replacement power adapters<br>To: "Community Support Volunteers -- who help respond to help AT <a href="http://laptop.org">laptop.org</a>" <<a href="mailto:support-gang@lists.laptop.org">support-gang@lists.laptop.org</a>><br>
<br><br><div class="Ih2E3d">On Thu, May 22, 2008 at 1:21 AM, Ixo X oxI <<a href="mailto:ixo@myna.ws">ixo@myna.ws</a>> wrote:<br>
> Some interesting news on compatible adapters...<br>
><br>
> I just recently purchased a Linksys (or was it a D-Link?) wireless adapter,<br>
> and the adapter fits like a charm. (12 V 2.25 amp)<br>
><br>
> So that got me thinking, and dug through my pile of various adapters.<br>
><br>
> (Laptop - IBM Thinkpad 770E), 16V , 3.36 amp<br>
> (Laptop - HP pavalin ze1250), 19V , 3.95 Amp<br>
<br>
</div>Best fit I've found was the power brick supplied with the Netpliance<br>
I-Opener boxes. Sadly, those are even harder to find than the real<br>
OLPC ones.<br>
<div class="Ih2E3d"><br>
><br>
> Also just in the last few days, I've developed some connections with two<br>
> local electronics recyclers who can set aside a select few of specific items<br>
> for me. One of the items I was thinking could be power adapters... with the<br>
> correct plug end.....<br>
><br>
> So... can the XO really handle ANY DC voltage between 12V and 24V ? Any<br>
> amps ?<br>
><br>
> Will all of the above work ok? What is the best range (or most effective<br>
> combination) for Amp's and total wattage ? (i.e. 12v @ 1amp vs 24v @ 500<br>
> milli-amp = 12 Watts)<br>
<br>
</div>==VOLTAGE== "VOLTS"<br>
The XO 'likes' around 12-14 volts, but should be able to charge<br>
(slowly and inefficiently) down to about 9V.<br>
DC-only and center pin positive. Both are critical. Make sure you<br>
check this for any re-tasked power supply you want to try.<br>
<br>
I would avoid a power supply offering more than 25 volts, or less than<br>
9. But these are unlikey anyway.<br>
<br>
==CURRENT== "Amps"<br>
The 'Amps" rating is a measure of how much current the supply will<br>
allow a device to pull before (essentially) blowing an internal fuse<br>
and killing the power adapter. You'll ideally want a supply that is<br>
comfortable supplying about 1.5 amps (which is pretty beefy) because<br>
then the XO will never ask for more than the power adapter can supply.<br>
<br>
The risk of using a power supply with a smaller 'Amps' rating is that<br>
the fuse will blow (in the power adapter) which will kill the power<br>
adapter.<br>
<br>
Any power supply with a greater-than-1.5 Amps rating will be fine,<br>
with the understanding that a) it will be unnecessarily more<br>
expensive, and b) there's a risk that whatever is drawing the power<br>
(the XO) will develop a fault and draw more than 1.5 amps, but less<br>
than the overcurrent protection of the power supply, and so the<br>
failsafe mechanism will fail to trip (a fancy way of saying the fuse<br>
won't blow.)<br>
<br>
==POWER== "Watts"<br>
The other common rating of a power supply is the power, measured in<br>
Watts. This is usually a rating of how much (maximum) the power<br>
adapter will *consume* (so it's listed as an input parameter) and<br>
includes power lost to the AC/DC conversion process.<br>
<br>
The XO consumes 17 Watts of power at maximum draw. So if the power<br>
supply indicates it uses less than 17 W, it won't supply a full 17 W<br>
onward to the XO.<br>
<br>
(That's important for the alternative energy folk as well: if you're<br>
trying to find a solar panel, hand crank, wind turbine or perpetual<br>
motion machine to run an XO, make sure it can supply enough power to<br>
run a 15-20W lightbulb over a period of hours or you won't be matching<br>
the standard power needs of an XO. That's a LOT of cranking over a<br>
period of 2 hours. Hand crank flashlight/cell phone rechargers<br>
generally provide less than 5 volts and total power measured in<br>
milliwatts. These just won't cut it for powering the XO.)<br>
<br>
======<br>
I have found two viable alternative power supplies:<br>
<br>
The first the 19V 1.84A (roughly 80 watts consumed) power adapter<br>
from the Netpliance I-Opener mentioned above. The power plug is as<br>
close to an exact part match as I've been able to find. (But it's not<br>
green). The bad news; these are unsourcable parts.<br>
<br>
The other is a 12V DC, 500 mA (0.5 Amp) power supply with a close-fit<br>
plug. This unit:<br>
1. is under-powered (only rated for 500mA vs. 1420mA for the OLPC Green supply)<br>
2. gets hot when charging an XO.<br>
3. has a loose-fit plug which occasionally needs 'wiggling'.<br>
4. is NOT a lead-free device, so probably is not appropriate for children.<br>
<br>
The good news is that these will recharge an XO (a good workaround<br>
solution for someone who's only XO power supply has failed, leaving<br>
their XO otherwise unpowered) and are available in my area. ($10 gets<br>
you the 500mA power adapter, a 12V car adapter with the same plug, and<br>
a wind-up flashlight/weather radio to boot)<br>
<div class="Ih2E3d"><br>
--<br>
Steve Holton<br>
<a href="mailto:sph0lt0n@gmail.com">sph0lt0n@gmail.com</a><br>
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