Michael Black wrote:> > And even worse, -5 plus +12 is 7 volts, the minus > subtracts from the positive.No, it doesn't. The -5 V supply has it's positive end connected to common, so they add. +5 V & +12 V supplies would have 7 V between the outputs.
DC 17V from PC power supply?
Started by ●June 25, 2013
Reply by ●June 25, 20132013-06-25
Reply by ●June 25, 20132013-06-25
"John G" <greentest@ozemail.com.au> wrote in message news:tdOdnWvxEqI1G1TMnZ2dnUVZ_uednZ2d@westnet.com.au...> Mr. Man-wai Chang submitted this idea : >> 1. If I shorted the +5V and +12V in the molex connector, >> would I get +17V? What's the max. current? >> >> 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A? >> Would it hurt the battery? > > NO! > Shorted is the correct description. > They are both referenced to ground so MAGIC SMOKE will result. :-?The correct term is: "let the magic smoke out".
Reply by ●June 25, 20132013-06-25
"Mr. Man-wai Chang" <toylet.toylet@gmail.com> wrote in message news:kqc53t$th6$2@dont-email.me...> On 25/06/2013 8:01 PM, John G wrote: >> NO! >> Shorted is the correct description. >> They are both referenced to ground so MAGIC SMOKE will result. :-? > > OTOH, should I attempt -5V and +12V pins at the power connector? Or should > I try +5V and -12V? > > Which one is safer and could supplies 4A?On older PSUs, the -12V had a 7912 regulator (1A max). Your best bet is an open frame 5 & 12V switcher that can be modified. You'll probably find a TL431 programmable zener with sampling resistors connected to the 5V rail, with suitable modification of the resistors, you can sample the 12V rail instead - if you adjust the resistor values to get 17V, watch the voltage ratings of the electrolytics or you'll get loud bangs and confetti (and let the magic smoke out). If you find a surplus Aztec open frame switcher - they use a house coded TL431, but its obvious when you see it.
Reply by ●June 25, 20132013-06-25
"Michael Black" <et472@ncf.ca> wrote in message news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org...> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote: > >> On 25/06/2013 8:01 PM, John G wrote: >>> NO! >>> Shorted is the correct description. >>> They are both referenced to ground so MAGIC SMOKE will result. :-? >> >> OTOH, should I attempt -5V and +12V pins at the power connector? Or >> should I try +5V and -12V? >> > The minus supplies, if they are even still there, have minimal current, > were way in the beginning because RAM might have needed some negative > voltage (I can't remember if those RAM were still in existence in 1981The original 5150 PC had provision for 3 rail RAM, selected by the configuration DIP switches. I have yet to aquire a 5150 board that hadn't been fucked up by someone messing with the DIP switches!
Reply by ●June 25, 20132013-06-25
"P E Schoen" <paul@peschoen.com> wrote in message news:kqcl62$rtn$1@dont-email.me...> "Mr. Man-wai Chang" wrote in message news:kqbv6h$tms$1@dont-email.me... > >> 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A? Would >> it hurt the battery? > > You can probably use a surplus or used notebook supply of similar specs. > Here's one with 19V and 2.65A for just $4: > http://www.mpja.com/19-Volt-Desktop-Power-Supply-265A-EIAJ-Plug/productinfo/19078%20PS/ > > And if you need 4.74A and can spare $15: > http://www.mpja.com/19V-474A-Desktop-Supply-Delta/productinfo/30336%20PS/In the UK; Maplin sells a universal laptop PSU with a voltage selector switch and an assortment of power jack attachments. This device depends on the laptop having its own internal charging circuit, its not intended for charging any battery directly. Most developed countries probably have a better choice than our just Maplin.
Reply by ●June 25, 20132013-06-25
"Michael Black" <et472@ncf.ca> wrote in message news:alpine.LNX.2.02.1306251529490.5374@darkstar.example.org...> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote: > >> >> 1. If I shorted the +5V and +12V in the molex connector, >> would I get +17V? What's the max. current? >> > No, because probably one side of each is already grounded inside the pwoer > supply. > >> 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A? >> Would it hurt the battery? >> > NO, because these likely are fancy batteries and you don't just push > current through them, it has to be controlled based on the state of the > battery.If its a lithium battery - charging with anything other than properly designed circuitry can be very dangerous!
Reply by ●June 25, 20132013-06-25
On Tue, 25 Jun 2013, Ian Field wrote:> > > "Michael Black" <et472@ncf.ca> wrote in message > news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org... >> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote: >> >>> On 25/06/2013 8:01 PM, John G wrote: >>>> NO! >>>> Shorted is the correct description. >>>> They are both referenced to ground so MAGIC SMOKE will result. :-? >>> >>> OTOH, should I attempt -5V and +12V pins at the power connector? Or should >>> I try +5V and -12V? >>> >> The minus supplies, if they are even still there, have minimal current, >> were way in the beginning because RAM might have needed some negative >> voltage (I can't remember if those RAM were still in existence in 1981 > > The original 5150 PC had provision for 3 rail RAM, selected by the > configuration DIP switches. > > I have yet to aquire a 5150 board that hadn't been fucked up by someone > messing with the DIP switches! >I'd forgotten about the dip switches on those. But how many were actually shipped with low density RAM? I thought it was the 4K RAM that needed negative voltage, and I thought by the time the IBM came out, it would use 64K RAM, which I thought did away with the need for negative voltage. Michael
Reply by ●June 25, 20132013-06-25
Michael Black wrote:> > On Tue, 25 Jun 2013, Ian Field wrote: > > > > > > > "Michael Black" <et472@ncf.ca> wrote in message > > news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org... > >> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote: > >> > >>> On 25/06/2013 8:01 PM, John G wrote: > >>>> NO! > >>>> Shorted is the correct description. > >>>> They are both referenced to ground so MAGIC SMOKE will result. :-? > >>> > >>> OTOH, should I attempt -5V and +12V pins at the power connector? Or should > >>> I try +5V and -12V? > >>> > >> The minus supplies, if they are even still there, have minimal current, > >> were way in the beginning because RAM might have needed some negative > >> voltage (I can't remember if those RAM were still in existence in 1981 > > > > The original 5150 PC had provision for 3 rail RAM, selected by the > > configuration DIP switches. > > > > I have yet to aquire a 5150 board that hadn't been fucked up by someone > > messing with the DIP switches! > > > I'd forgotten about the dip switches on those. > > But how many were actually shipped with low density RAM? I thought it was > the 4K RAM that needed negative voltage, and I thought by the time the > IBM came out, it would use 64K RAM, which I thought did away with the need > for negative voltage.The early PC motherboards were shipped with four banks of 16K RAM.
Reply by ●June 25, 20132013-06-25
Mr. Man-wai Chang wrote:> > 1. If I shorted the +5V and +12V in the molex connector, > would I get +17V? What's the max. current? > > 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A? > Would it hurt the battery? >No Jamie
Reply by ●June 26, 20132013-06-26
Guess this project is too dangerous for a beginner! Thank you all! :) -- @~@ Remain silent. Nothing from soldiers and magicians is real! / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (Fedora 18 i686) Linux 3.9.6-200.fc18.i686 ^ ^ 12:30:01 up 21:59 0 users load average: 0.04 0.04 0.05 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
