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Author Topic: Cheap 12volt(ish) PSU  (Read 4016 times)

Martin (Admin)

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Cheap 12volt(ish) PSU
« on: November 02, 2008, 12:32:40 pm »

I needed a 12volt DC supply for a nicad charger..... without spending any money!
I rummaged through the old Laptop PSU box at work and found a Toshiba 15V 3A
Works a treat!  :-))
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #1 on: November 02, 2008, 01:36:42 pm »
What a good idea Martin

....got any more  :} :}
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #2 on: November 02, 2008, 02:26:58 pm »
Just had a quick look at our home laptops and they all seem to be 19v and my charger is a max input of 15v.

Is that an older power supply??
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andyn

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Re: Cheap 12volt(ish) PSU
« Reply #3 on: November 02, 2008, 03:08:26 pm »
Would be from when laptops had Ni-Cd's, ah the joys of the poorness of old laptops, I have one in the loft somewhere.
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Martin (Admin)

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Re: Cheap 12volt(ish) PSU
« Reply #4 on: November 03, 2008, 09:03:52 am »
Quote from: Tester on November 02, 2008, 01:36:42 pm
What a good idea Martin

....got any more  :} :}

Might do!......  :P
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #5 on: November 03, 2008, 03:11:18 pm »
Just had a look in the loft at my old junk and all I found was a massive wasp's nest  !!!!

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andrewh

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Re: Cheap 12volt(ish) PSU
« Reply #6 on: November 03, 2008, 03:57:21 pm »
In a similar vein, its a rare house that doesn't have a dead PC or two lying around. 

The Power Supply Units of PCs produce (at least) 12VDC and 5VDC from the mains supply, and can supply a fair current at 12V.  I'm not sure of the ratings, but its certainly enough to run a hot wire cutter or act as a bench power supply.  PSUs seem to be rated about 400W , so if we lose 25% in conversion there should be 300 watts or so available at the lower voltages.  300W at 12V is 25Amps (but it will not be possible to have it all as 12V, probably)

Even though the PSUs come in a complete metal box, with the Mains components well insulated please be aware that there is mains voltage on the input side, and keep youself safe.  Leave the PSU in the computer case if you wish to be completely safe.

The power supplied to the computer is at low voltages and appears on cable leads with plugs fitted.  use a voltmeter to find out what voltages are present - or even better check this reference which gives the colours, powers and plug types fitted
http://en.wikipedia.org/wiki/Computer_power_supply

If you were to make a hot-wire cutter, you might consider using your brushed motor ESC as the power controller, and drive it with a servo tester so that you can dial up the power and temperature of the wire by twiddling the knob.
andrew
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andrewh

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Re: Cheap 12volt(ish) PSU
« Reply #7 on: November 03, 2008, 04:00:04 pm »
tester
- not only are wasps nests very beautiful  - you could salvage it and mould an S-boot hull (pre-camouflaged) with the wasp paper

andrew
if its free its essential
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chingdevil

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Re: Cheap 12volt(ish) PSU
« Reply #8 on: November 03, 2008, 04:27:13 pm »
If you have an old PC check its power supply and then check out this article, it works really well.

http://web2.murraystate.edu/andy.batts/ps/powersupply.htm


Brian
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #9 on: November 03, 2008, 04:43:39 pm »
Hi Andrew

My wife dosen't agree with the beauty.... words to the effect "get rid of it now" came as she disappeared rapidly over the horizon  :-) :-)

Richard
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andrewh

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Re: Cheap 12volt(ish) PSU
« Reply #10 on: November 03, 2008, 04:50:44 pm »
tester,

I was assumng it was wasp-free! 
Me, I love the mottled shades of greys and browns that make up the paper  - reminds me of some of the mottled colour schemes used by the axis.
Curiously, my wife likes them as well

BTW; Which did you decide to keep? :}
andrew
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Martin (Admin)

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Re: Cheap 12volt(ish) PSU
« Reply #11 on: November 03, 2008, 04:51:55 pm »
Good point Brian, I forgot that I use a PC PSU for my other battery charger.

There are many proper/elaborate conversion for PC PSU around but with mine, I only bridged
the green wire to one of black wires, seems to work for me!

NB. For safety reasons, only attempt this type of modification if you have the qualifications,
experience and wherewithall to do this.

http://www.modelboatmayhem.co.uk/forum/index.php?topic=10935.msg102278#msg102278

http://modtown.co.uk/mt/article2.php?id=psumod
http://www.gideontech.com/content/articles/196/1



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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #12 on: November 03, 2008, 05:09:09 pm »
Can I ask a quick question. My Triton Charger, discharger and cycler says it needs 10.5 - 15v DC input and then says " to achive Triton's maximum potential, the power source must be capable of delivering at least 13 amps of current while maintaining 12 volts DC"

Will one of these modified psu's or a laptop power supply work?. I only use the charger for cycling nicads and charging Nimh at the moment.

PS The wife...  O0 O0
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Martin (Admin)

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Re: Cheap 12volt(ish) PSU
« Reply #13 on: November 03, 2008, 05:22:50 pm »
I would be more worried about a charger requiring 13Amps than anything else!
Yes a modified PC PSU should power almost any charge.
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Sandy Calder

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Re: Cheap 12volt(ish) PSU
« Reply #14 on: November 03, 2008, 10:42:26 pm »
.....a YT50 50 watt halogen bulb transformer(£4.50 from TLC-direct) and vero rectifier/filter.
Another for the "if you have the qualifications,experience and wherewithall to do this." types.

At 31 kHz it needs a hefty rectifier and interference filter (vero circuit) but the transformer is protects against shorts,overheating and mains bourne surge transients.

Regards
Sandy the cheapskate.
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portside II

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Re: Cheap 12volt(ish) PSU
« Reply #15 on: November 03, 2008, 11:55:34 pm »
save time converting psu's from pc's and other things ,why not just buy a regulated psu ,the ones used by cb'ers to power their radios.
They are not all that expensive these days , a good site is knights wher they have a range of psu's from 2a - 60a and some have variable outputs of 3-15v.
daz
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Martin (Admin)

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Re: Cheap 12volt(ish) PSU
« Reply #16 on: November 04, 2008, 07:54:05 am »
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #17 on: November 04, 2008, 07:57:58 am »
Thanks for the site link Martin, but still more expensive than a 2nd hand PSU. I think I'll have a look at the cheap option
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Martin (Admin)

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Re: Cheap 12volt(ish) PSU
« Reply #18 on: November 04, 2008, 08:06:27 am »

 :-))... but if you don't happy about electrics, there always a choice.
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Tester

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Re: Cheap 12volt(ish) PSU
« Reply #19 on: November 04, 2008, 10:53:21 am »
or just get another second hand car battery and continue to charge in the garage, only trouble is that it's a bit cold outside....
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