Godwin's law.
Trumps 'em all. -sc From: Maglinger, Paul [mailto:pmaglin...@scvl.com] Sent: Friday, February 25, 2011 4:56 PM To: NT System Admin Issues Subject: RE: QUICK question... A/C adapters Don't leave out Thévenin's theorem. :-) -Paul From: Jonathan [mailto:ncm...@gmail.com] Sent: Friday, February 25, 2011 3:52 PM To: NT System Admin Issues Subject: Re: QUICK question... A/C adapters +1 SC is dead on here. Match the voltage (and the polarity, if DC), and match or exceed the current rating (amps) or the power rating (watts) and you'll be fine. Typically (for barrell connectors, anyway, you'll find that the size of the connector has to do with the voltage and or amperage of the supply. On a related note, I always appreciate when one of my computer geek colleagues quotes Ohm's law. ....or Kirchhoff's law... The sum of the currents entering a circuit equal the sum of the currents exiting the circuit. Jonathan On Fri, Feb 25, 2011 at 1:20 PM, Steven M. Caesare <scaes...@caesare.com> wrote: No, Ben is correct here. The resistive load (simplifying, as most modern load have inductive or capacitive components in addition to purely resistive loads), is heat will determine how much he current draw will be. Ohms law tells us I = V/R I-current V=voltage R=resistance Therefore if your supply voltage(V) is 14 volts, and the load resistance(R) is 7 ohms, then the current draw (I) will be 2 amps. Thus your power supply must be capable of supplying at LEAST 2 amps[1], it may be able to supply more, but the system would simply never draw it. A 500A power supply would no more require the load to "dissipate more heat" it than a 2A power supply would. -sc [1] And incidentally, power (W) = V*A. Therefore our theoretical power supply in this case would be supply 28W of power[2]. I not this because power supplies are often capable of varying voltage and/or are rated in watts. [2] Ignoring power efficiency factors for the moment. From: Jonathan Link [mailto:jonathan.l...@gmail.com] Sent: Friday, February 25, 2011 1:07 PM To: NT System Admin Issues Subject: Re: QUICK question... A/C adapters It would depend on whether you can trust the resistor to dissapate the extra heat generated by additional current. It's not something I would do over the long term... On Fri, Feb 25, 2011 at 12:57 PM, Jim Holmgren <jholmg...@xlhealth.com> wrote: Matt, I believe you are correct. Also not an EE, but in about 10 years of working for RadioShack, that was the mantra. The device will only draw the amperage it needs, but it must have the correct voltage. Jim Jim Holmgren Senior Manager, Infrastructure Services XLHealth Corporation The Warehouse at Camden Yards 351 West Camden Street, Suite 100 Baltimore, MD 21201 410.625.2200 (main) 443.524.8573 (direct) 443-506.2400 (cell) www.xlhealth.com <http://www.xlhealth.com/> -----Original Message----- From: Matthew W. Ross [mailto:mr...@ephrataschools.org] Sent: Friday, February 25, 2011 12:49 PM To: NT System Admin Issues Subject: RE: QUICK question... A/C adapters I am not an electrical engineer, so please do not take this as power supply advice: I have been told that as long as the voltage is correct, you can go over on the amperage with your PS. So, if you have something that requires 9V, 1 amp PS, and you have a 9 volt, 2 amp... you're good to go. The device will only pull as much amperage as it requires. Voltage is specific, as I'm told. Don't mess with it. AC and DC don't mix, etc, etc... Again, don't use this as any kind of real advice. Somebody with real electrical engineering experience can verify or tell me I've been told wrong. Sm:)e. --Matt Ross Ephrata School District ----- Original Message ----- From: Maglinger, Paul [mailto:pmaglin...@scvl.com] To: NT System Admin Issues [mailto:ntsysadmin@lyris.sunbelt-software.com] Sent: Fri, 25 Feb 2011 09:32:57 -0800 Subject: RE: QUICK question... A/C adapters > I go with 3rd party when there is a significant cost savings. Case in > point, we use a particular print server. The power supplies are > notorious for going bad. We cannot purchase the OEM power supplies > alone and the entire package runs about $120. I found replacement power > supplies for $7.50 online. Just make sure that the voltage, current, > polarity, and the connector size all match up! > > I have been known to go slightly higher in the current capacity so they > don't run as hot. Note that I said "slightly". > > -Paul > > -----Original Message----- > From: John Aldrich [mailto:jaldr...@blueridgecarpet.com] > Sent: Friday, February 25, 2011 11:27 AM > To: NT System Admin Issues > Subject: RE: QUICK question... A/C adapters > > Thanks guys... I'll keep monitoring, although it sounds like the > consensus > of opinion so far is that 3rd party is OK. :-) > > > > > -----Original Message----- > From: Matthew W. Ross [mailto:mr...@ephrataschools.org] > Sent: Friday, February 25, 2011 12:10 PM > To: NT System Admin Issues > Subject: RE: QUICK question... A/C adapters > > *grabbs the "Dell" AC adapter under his desk and checks who actually > manufactured it.* > > It appears that Dell doesn't make their own, this one is made by Delta. > (A > well known PS manufacturer.) > > I'm sure Dell has some very specific requirements for their power > supplies. > > But, I will say that any reputable aftermarket PSs are likely trying to > be > as close to the specs as possible for the intended use. YMMV. > > > --Matt Ross > Ephrata School District > > > ----- Original Message ----- > From: Ames Matthew B > [mailto:mba...@qinetiq.com] > To: NT System Admin Issues > [mailto:ntsysadmin@lyris.sunbelt-software.com] > Sent: Fri, 25 Feb 2011 > 08:59:07 -0800 > Subject: RE: QUICK question... A/C adapters > > > > Personally I would get a proper one direct from the manufacturer. You > > hardly want a cheapo PSU bein left on and causing a fire. > > > > Pretty sure that Dell a good few years ago did a recall for a dodgy > > batch of laptop PSU (at least in the UK), I doubt you would get that > > sort of service from an Amazon seller. > > > > > > -----Original Message----- > > From: John Aldrich [mailto:jaldr...@blueridgecarpet.com] > > Sent: 25 February 2011 16:47 > > To: NT System Admin Issues > > Subject: QUICK question... A/C adapters > > > > Are A/C adapters something you guys would ONLY buy from the OEM or is > an > > aftermarket OK on something like that? I got the OEM to come down > about > > $10, but they're still about $10 higher than Amazon... if you guys > think > > that's something that should come from the OEM, I'll go with them. > I'll > > look for your answers until Monday and make a decision based on the > > consensus of opinion then. :-) (See... I can be patient. :-)) > > > > > > > > > > > > > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ > > <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > > > --- > > To manage subscriptions click here: > > http://lyris.sunbelt-software.com/read/my_forums/ > > or send an email to listmana...@lyris.sunbeltsoftware.com > > with the body: unsubscribe ntsysadmin > > This email and any attachments to it may be confidential and are > > intended solely for the use of the individual to whom it is > > addressed. If you are not the intended recipient of this email, > > you must neither take any action based upon its contents, nor > > copy or show it to anyone. Please contact the sender if you > > believe you have received this email in error. QinetiQ may > > monitor email traffic data and also the content of email for > > the purposes of security. 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Si usted no es el destinatario, por favor, póngase en contacto con el remitente por teléfono y destruir todas las copias del mensaje original ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin -- Jonathan, A+, MCSA, MCSE ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to listmana...@lyris.sunbeltsoftware.com with the body: unsubscribe ntsysadmin
