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Old 01-26-2006, 03:13 AM   #16
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personally i would not bother. sure it may be a cheap alternative but if it's not right you could end up doing more harm than good.

i would save your dosh & get something that is purpose built.
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Old 01-26-2006, 03:37 AM   #17
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Quote:
Originally Posted by Glowster21
It is a 12volt bulb on the 5 volt line, and a 1 ohm resistor on the 5 volt line. When it stays on, I can charge a battery at 6 amps and break in a motor etc. It is a 3oowatt supply that was new.
What is the wattage of the 12v bulb? It actually sounds like there is too much load, which is tripping the PSU's overload protection cut-off.

IMO I wouldnt use a 300w PSU, I recommend 400w minimum.

What are the amp ratings on the PSU label for the 3.3v, 5v, & 12v lines?


@Flysti- purpose built? Most purpose built Power supplies ARE computer PSU's!

There is no harm in saving money AND ending up with a better product as long as you know what you are doing. On any related thread about converting PSU's I make sure to warn people of the possible dangers if they're not careful.
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Old 01-26-2006, 05:03 AM   #18
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well if you buy somthing purpose built you have fall back if it fails. + the fact that some i have seen (computer psu) are real dodgy & should not be allowed to be used.
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Old 01-26-2006, 05:39 AM   #19
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So how many amps does this throw out? I just bought charger blinged up with some neon lights and a lighted fan. Needs 15 amps for it to really work good.
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Old 01-26-2006, 04:36 PM   #20
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Quote:
Originally Posted by flysti
well if you buy somthing purpose built you have fall back if it fails. + the fact that some i have seen (computer psu) are real dodgy & should not be allowed to be used.
That gets back to my point about "knowing what you are doing".

Regardless of how many warnings or disclaimers anyone makes, there is nothing to actually stop someone from making one, even if they don't have the expertise or knowledge to do it properly.

Unfortunately, it is human nature to want to attempt to do something that may be beyond our capabilities.
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Old 02-05-2006, 08:42 AM   #21
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(12+ yellow wire) to (black wire) OR (yellow wire 12+) to (12- wire)
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Old 02-22-2006, 02:55 PM   #22
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Sorry to bring this back up but i built one and it was REALLY REALLY simple. I even did some adding/removing wires straight from the circut board. Here is a pic:



The only change from that pic now is that ive added a small heat sink to each of the resistors. Thanks for all the help guys!
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Old 02-22-2006, 03:20 PM   #23
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i've put my resistors (same big ceramic types) directly in the airflow in the psu housing.
disconnected the fan from the circuit board and reconnected them to 12v connections.

no further heatsinks needed

although the only glitch that happens sometimes is when i pull a battery of the charger or run a powerful motor on my motor master the supply cuts out... have to pull out the power cord for about 30 seconds and reconnect again...
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Old 02-22-2006, 03:49 PM   #24
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Quote:
Originally Posted by aN4rK1
Sorry to bring this back up but i built one and it was REALLY REALLY simple. I even did some adding/removing wires straight from the circut board. Here is a pic:



The only change from that pic now is that ive added a small heat sink to each of the resistors. Thanks for all the help guys!


damm that is dodgy
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Old 02-22-2006, 04:03 PM   #25
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dodgy? lol
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Old 03-02-2006, 08:58 AM   #26
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Exclamation Not working...

Got a new 400 watt ps.

isolated all the lines.

Yellow +12
Black Ground
Red +5

Orange +3.3 (cut all off)****
White -12 (cut off)
Purple +5 STDBY (cut off)

Grey Pwr Good
Green PS on

I have a 10 ohm 10 watt resistor for the load.

I have the resistor to the +5 and Ground I have the Green to Ground

I am not sure if I am to do anything with the Grey, also some articles say that I need a sense wire (pin 11 from block connector) wired to +3.3 - I had no identified sense wire (orange wire at pin 11)

MY point.. this is not powering up.. the fan flicks on.. and nothing more.

Any ideas? Change the load? Look for this sense wire? I have seen articles where it says to put the GREY pwer good to +5??

Thanks

James
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Old 03-02-2006, 09:21 AM   #27
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Quote:
Originally Posted by Bikerbob
Got a new 400 watt ps.

isolated all the lines.

Yellow +12
Black Ground
Red +5

Orange +3.3 (cut all off)****
White -12 (cut off)
Purple +5 STDBY (cut off)

Grey Pwr Good
Green PS on

I have a 10 ohm 10 watt resistor for the load.

I have the resistor to the +5 and Ground I have the Green to Ground

I am not sure if I am to do anything with the Grey, also some articles say that I need a sense wire (pin 11 from block connector) wired to +3.3 - I had no identified sense wire (orange wire at pin 11)

MY point.. this is not powering up.. the fan flicks on.. and nothing more.

Any ideas? Change the load? Look for this sense wire? I have seen articles where it says to put the GREY pwer good to +5??

Thanks

James
You need to wire the ground wire to the PS on wire (black to green) and also you can bypass the "voltage sense" by wiring a 3.3v wire to the grey wire.
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Old 03-02-2006, 09:28 AM   #28
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ok, I have done the green to ground in my original test - did not work.

The Grey (pwr good) you think to +3.3? I tried it to +5 that did not work.

The ps I have does not have an actual sense wire(usually brown).. when I look at all the +3.3 they all start in the same block on the circut board.

I will have to solder an Orange +3.3 wire back in.. as I cut them all off.

Will give this a try tonight. You think the 10 OHM 10W should be enough load though??

James
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Old 03-02-2006, 11:50 PM   #29
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Ok, got it working!!

The 10 ohm 10watt was not enough.. a 30 OHM 10 Watt was good.

Now I have just one last problem. If I hook it up to a charger that changes power quickly then it shuts off. I know this is some kind of protection built into the ps, is there a work around it??

I dont have the grey power good hooked up btw.. did not need it.

James
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Old 03-03-2006, 12:01 AM   #30
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The green wire should be just a momentary connection to ground to turn on a power supply. All you have to do is touch it to ground and then remove it.

For mine I used a momentary switch and I just press it once to turn my supply on and press and hold it for a couple seconds to turn it off.
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