Re: LF: Noise R75 - rs232 from smpsu -

[Andy Talbot <andy.g4jnt@googlemail.com>]

I've just ordered a couple of the DS2502 one-wire EEproms contained in the Dell PSU to tray hacking the contents to make a custom PSU.   But there's a long delivery time on them  from Farnell, so that's one project on hold until October.

Look easy enough to read and write, but they will need a custom PIC interface as the one-wire protocol is time-slot based.   Standard EEProm programmers can't do the job..

 

Apparantly, from people who have managed to read the Dell PSU  EE contents, it contains ASCII text giving the voltage and current rating, and the same serial number as appearing on the label.

 

One disconcerting finding - every chip has a unique fixed 48 bit serial number 'lasered' into it at manufacture.   So any Dell PSU, (or in fact any other product that uses these chips as an electronic serial number) can be uniquely identified - if anyone ever bothered to keep a record.   Don't think it can be read out via the Windoze operating system.   Bit if the part of the Bios that read the PSU data could be identified, its possible to envision a piece of software that could tell you which PSU was plugged into it.    

Big Brother could be watching you even more closely.

 

Andy
www.g4jnt.com

On 26 July 2010 14:10, Dave Pick <davepick@btinternet.com> wrote:

Jean-Louis

I had a 12V car/aeroplane adaptor for one of my Dells, made by a company called LL Power inc.
Dell used to sell them as accessories. LL Power have a web-site at http://www.llpower.com
Remember that these switch-mode adapters will cause RF interference!

Dave G3YXM

---

From: "Jean-Louis.RAULT@fr.thalesgroup.com" <Jean-Louis.RAULT@fr.thalesgroup.com>
To: rsgb_lf_group@blacksheep.org
Sent: Monday, 26 July, 2010 8:13:05
Subject: RE: LF: Noise R75 - rs232 from smpsu -

Dear all,

 

Do you know if there is any 12 V DC power supply supplier for the DELL laptops ?

 

Jean-Louis F6AGR

---

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Andy Talbot
Sent: Friday, July 23, 2010 11:05 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Noise R75 - rs232 from smpsu -

Yes, I've played with running laptops including Dells from all sorts of power supplies.  The nominal voltage can go a goodly 10 - 20% either way before it flags an error - and they seem to detect over voltage and take evasive action, although couldn't guarantee all do.

 

BUT there's a big snag with Dells.  If youv'e got one with the three way coaxial DC connector (it has a very thin centre pin) - the PSU contains a DS2502  one-wire EEPROM..   The Laptop interrogates the PSU to find out if its satisfactory and if the EEPROM isn't present, the laptop will use the external power, but refuse to charge the battery.    On a 12V input mobile PSU I had to butcher a surplus Dell black brick to get the EEPROM and incorporate it into the connector for the new PSU.

 

Those EEPROMS are supposed to be easy enough to read, so when I need one again, will read the contents and stick them into a fresh chip.

 

Andy
www.g4jnt.com

On 23 July 2010 21:47, Laurence KL7UK <hellozerohellozero@hotmail.com> wrote:

Anyone done any common mode noise mitigation from the RS232 port of the R75 Rx> - the noise coming up from the SMPSU/processor from the old Dell puter - cable is double screened - choking off using J (75) type has seen little improvement - this is my last hurdle to unimpeded remote rx on 137 - any pointers appreciated - everythings bonded and Ive tried the on/off earth tricks at various locations -
 
Anyone had any success of powering a Dell D series from a non standard non switched PSU? (the noise goes away when the DC from the Black Dell brick is removed but it may also be partially screen/processor noise...)
 
with thanks
 
Laurence Kl7UK

---

The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail. Get busy.