Home built power supply

[PB]

My old car battery charger has been sitting in the garage since I bought a more modern one a while back. I decided to convert the old charger into a regulated bench power supply to charge my lipos so I gutted the old charger, keeping only the case with its transformer and rectifier still mounted in it. Only 11 additional components costing just £8 are required to build the bench power supply. These components are assembled on a small piece of veroboard which is mounted in the existing case. The result is a high quality variable 0v - 14v 10A regulated bench power supply and If anyone's interested in the cicuit diagram I'll happily post it here.

[IanN]

Yes please

Maybe a quick "how do I" idiot's guide, for those of us who aren't totally au fait with circuit diagrams would also be of interest

[PB]

OK Ian, circuit attached. I posted this thinking that only hobby electronics folks might be interested who would be able to work from a circuit diagram. With so few components it's quite simple to mount them onto a small piece of strip board 'on the fly' without a formal layout plan. I'll work on the 'how do I' guide anyway in case anyone asks for one, but even so it will take some electronics knowledge to do the job. The TIP 162 is on a heat sink and I also connected an old computer CPU cooling fan internally to the output terminals and glued it in place to blow air onto the heat sink. I limited the current to 6.5A with a 0.1 ohm 3W resistor between pins 2 and 3. The power supply works very well and charges my 4S 5000 lipos at 4.5A quite comfortably.

[Speedster]

The power suply,s we use in the club are a powersuply for scrap PC,s.

You can find them at the local scrapyard, and they are easy to remove from the pc.

Normaly they can give from 12 to 15 Amp.

12 v + is the all the yellow wires and - is the all the black.

To start it up, you must make a permanent assembling of the green wire and a black one.

Then it will start up and the cooling fan will turn.

Easy and cheap.

S

[PB]

Hi Speedster. Yes I have an old 300W ATX power supply that I've converted to a bench power supply but you need to be a bit careful. Some folks think that 300 watts = 25 amps at 12 volts, but that's not how it works in this case. A typical spec for a 300W ATX is: +5v @ 30A (red wires), -5v @ 0.5A (white wires), +12v @12A (yellow wires), -12v @ 0.8A (blue wires), +3.3v @14A (orange wires). They also have some huge capactors in there which remain charged to very high voltages for days after the PS has been switched off. So if people do go this route they should connect a 10 watt 12 volt car light bulb, (an interior festoon bulb is pefect), betwen each bunch of coloured wires and the black ground wires until the bulb dims and extinguishes, being extremely careful of course not to make contact themselves.

You're right that the computer ON switch connects the green to the black wire to enable the output voltages, but for safety it is essential that all power supplies have an indicator to show whether they are switched on or off, and a stock ATX PSU doesn't have this because it's normally an internal component. For safety's sake in your club you should do this by connecting an LED in series with a 330 ohm resistor between the grey power on wire, (LED anode), and any black wire, (LED cathode), mounting the LED in its holder in a hole drilled in the front of the case.

[Simon Chambers]

If you want a beefy power supply that is as solid as a rock and safe, imo you can't go much wrong with a XBox 360 power supply. Piece of cake to mod and the older original ones output ~17A at 12v. Much less faff than a PC psu.

I did a brief write up on my post near the end of this thread here.

Si.

[flight1]

Hi I have converted atx PC power supplies to power my 12v chargers etc and they have been very good and as the post be for and putting lamps on is a must. this has been a very cheep method of getting reliable regulated 12v power supplies, but as high power lipo etc have become more numerous the need for high out puts has be come a necessity. The solution and best and cheapest way of getting high power outputs is to use old server power suppies, they are buit to a high standard a lot better than the generic pc ones available. Thes power supplies will give 45A easily at 12volts.

most numerous is Hewlett pacard server switching power supply HP DPS-600PB like this one avail able on eby http://www.ebay.co.uk/itm/251014979830 very cheep and easily converted.

A thread that shows conversion here http://www.rcmf.co.uk/4um/index.php/topic,90276.msg1047696.html#msg1047696

Hops it helps

Cheer R

[Fun Flyer]

I went the ATX PC Power Supply route some time ago. However I found that when I try to use it to charge LiPos the LEDs on the charger pulse rather than staying on solid. Any suggestions as to why this would be?

[PB]

Fun Flyer if you're using a balancing charger then it will pulse between charging and balancing ususally at around one cycle per second. However, the LEDs on the charger itself usually don't reflect this pulsing and stay lit solidy. If you monitor the current drawn from the power supply though it will be pulsing. Even though it's pulsing, does your ATX nevertheless charge your Lipos?

[Fun Flyer]

PB, I didn't persevere when I saw the pulsing. I went back to my original power supply, built from mainframe computer parts. i.e. big transformer, big capacitor and big capacitor all nailed to a plank. Works perfectly and heats the workshop as well!

[PB]

Yes Fun Flyer, I used to have one of those under my workbench too, but I put it in a case after I knocked a cup of tea over it and blew every trip on the dist board which in turn spiked the hard drive on my PC and cost me dearly. The firework display was interesting though !!

[Fun Flyer]

Sorry, one of those big capacitors should have been a big rectifier. PB, I've only been using mine for about fifteen years so its a bit soon to get all fancy with a case.