Don't encourage -sc...his ego is insufferable as it is. ;) - WJR
On Fri, Feb 25, 2011 at 15:51, Jonathan <ncm...@gmail.com> wrote: > +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 >> >> >> >> >> >> -----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. 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