Dell 3330 laptop adaptor with 1-wire comms! - Page 1
Forum section: electronics / projects

author: picitup
author_rank: Regular Contributor
timestamp: December 11, 2015, 08:46:48 am
content: Hi AllI've been using 2 mains adaptors for a while, 1 clone and 1 pucker Dell. The pucker Dell one died, and I noticed the battery was no longer charging and the laptop was running slow.When I rebooted, I got an error message from the BIOS saying the adaptor could not be recognised and the laptop would be slowed down to compensate. As promised, the laptop rang like a dog. My first port of call was to update the BIOS as there was a 2015 release and mine was about 3 years old.Not so lucky. The BIOS update required a battery charge of a minimum of 10% in order to run. Makes sense, but didn't help me.Next I connected the laptop to my PPS2320a in parallel mode, so that's 19.5v at 6 amps. I rebooted and got the same error message. I was starting to think this was a motherboard issue.But not so. What I didn't realise was that the power plug had 3 connections, the middle pin being connected to a 1-wire device in the power supply which tells the bios the voltage, power etc of the supply so a simple PSU won't work properly.I got the info from here:http://hackaday.com/2014/03/03/hacking-dell-laptop-charger-identification/Next is to bust open the broken adaptor and remove the 1-wire device, then I can use it with any PSU.CheersSteve

author: crispy_tofu
author_rank: Super Contributor
timestamp: December 11, 2015, 08:59:12 am
content: Happened to me as well, only I was using a genuine adaptor. Turns out the circuitry that sensed this extra pin was fried...

author: ConKbot
author_rank: Super Contributor
timestamp: December 11, 2015, 09:06:52 am
content: To be fair, that isnt there *just* for consumer lock-in. They use the same connector for lots of models of laptops and chargers, so a 45W charger hooked up to a laptop that comes with a 330W power brick (http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=332-1432for gaming laptops apparently) its not gonna be able to do much with the laptop at full power.

author: picitup
author_rank: Regular Contributor
timestamp: December 11, 2015, 09:41:16 am
content: Yes I can see the point of it and it makes sense for the PSU to be able to identify it's capacities. There's also a massive price difference between OEM and clones. For my laptop, OEM is £58.79 and third party is £12.00, so 5 times more expensive. Given the volume they must sell, they must be making a good profit.Personally I'm going with my clone adaptor and the 1-wire chip from the bust OEM PSU.Thanks for reading....Steve

author: amyk
author_rank: Super Contributor
timestamp: December 11, 2015, 10:55:14 am
content: Interesting series on that here:https://hclxing.wordpress.com/2014/02/06/hacking-the-dell-laptop-power-adapter/https://hclxing.wordpress.com/2014/02/09/hacking-the-dell-laptop-power-adapter-part-ii-2/https://hclxing.wordpress.com/2014/02/09/hacking-a-dell-power-adapter-part-iii/https://hclxing.wordpress.com/2014/02/26/hacking-a-dell-power-adapter-final-not-really/The ultimate solution would be to move this chip inside the laptop, so you can accept a plain +/- power supply. If you want to use an MCU you could install a button that switches between input wattages.Quote from: ConKbot on December 11, 2015, 09:06:52 amIt is for lock-in, because otherwise they'd use something cheaper and simpler like a resistor, which is what the ThinkPads do:http://www.thinkwiki.org/wiki/Power_Connector#Signal_Pinhttp://www.thinkwiki.org/wiki/Power_Connector#Signal_Pin_2Note that Apple does a similar thing with its AC adapters:http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

author: picitup
author_rank: Regular Contributor
timestamp: December 11, 2015, 12:28:46 pm
content: Hmmm interesting. Thanks for all the links.Installing in the laptop would be the best solution I agree, but I'm probably going to wire the 1-wire device in line with a cable as it'll be quicker.Before I knew about the sensor, I was imagining the motherboard producing a large short duration current spike on the PSU across a resistor and the resistor was short circuit. Shows how wrong you can be.CheersSteve

author: tooki
author_rank: Super Contributor
timestamp: December 11, 2015, 05:55:35 pm
content: Apple also uses 1-wire on its power adapters, so that the laptop knows not to charge if it's on an underrated charger (e.g. 17" MacBook Pro on a MacBook Air charger), or on the airline cord.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: December 11, 2015, 07:07:13 pm
content: On my Dell Prescision M4600 I can disable the Adaptor-Check in the BIOS-Settings.I guess this is possible on other Dells too.

author: kolbep
author_rank: Frequent Contributor
timestamp: December 11, 2015, 07:51:44 pm
content: Apple Iphone Lightning Cables also have a chip in the Lightning Connector end.And since an update to IOS7, the iphones NO LONGER charge with a chinese cable.(I am talking about the cable itself. NOT the powersupply)before the IOS upgrade, it used to just warn you about incompatibility, but now you are SOL.Why do they do this?Because they do not want you to use a $1 Chinese cable, but they want to rip you off with their $25.00 cable that lasts less than a year

author: ajb
author_rank: Super Contributor
timestamp: December 11, 2015, 08:36:23 pm
content: I'm sure they don't mind the lock-in, but imagine that you're selling millions of devices to consumers, and many of them go out and buy the cheapest cables they can find that have so little copper in them that they can only handle a fraction of the current your device requires to charge. Now you have tens of thousands of customers coming to you complaining that the device doesn't charge and demanding that *you* replace it, and it can't possibly be the cable, and you're just trying to get them to spend more money by selling them your overpriced $25 cable which is exactly the same as the one they got from the internet for $3. When you sell enough devices, enabling your device to detect and reject an accessory that isn't known to be built to spec can mean massive savings just in support costs. Of course they aren't going to miss the opportunity to mark that accessory up and make some extra money in the process, but it's not necessarily only about greed. . .

author: German_EE
author_rank: Super Contributor
timestamp: December 11, 2015, 09:01:26 pm
content: Something similar happens on the Thinkpad machines. The inner and outer of the sleeve are the actual power connection and the center pin has either a resistor to ground or is open circuit. For the 90W PSU the pin is open circuit and a resistor tells the BIOS to reduce CPU speed because either a 65W or a 50W supply is being used.Easily hacked, remove the pin.

author: tooki
author_rank: Super Contributor
timestamp: December 12, 2015, 12:05:54 pm
content: Quote from: kolbep on December 11, 2015, 07:51:44 pmThe chip's primary function is to be a host adapter to whatever is on the other end of the cable, most commonly USB. That's because Lightning isn't an alternative plug for otherwise standard USB; it's a completely different interface. The ipad pro shows why: it apparently supports USB 3, with a hitherto unreleased cable.You can still get $2 Chinese cables that work fine, by the way (but it's true, not all do). I've just found their durability to be so bad that I don't bother with them any more.But regardless, the point of my Apple comment wasn't to start a bashing session, just to illustrate that using negotiated power delivery is actually quite common these days.