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Old 09-30-2004, 03:57 PM   #1
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Default Building a power supply

I am currently using a 4 cell 3000 pack on my lathe, but would like to also have a power supply to use.

Anyone know a place online where I can find a guide to building a power supply?

Any help is GREATLY appreciated.

Thanx.
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Old 09-30-2004, 04:04 PM   #2
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cant build it but you can buy it, you would have to be a genius to make one
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Old 09-30-2004, 04:08 PM   #3
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Pretty sure with some fairly basic physics you could knock up a power supply/ transformer. Best bet would be to buy a cheapish computer power supply and use the 5V line from that, i know theres a few guides on how to convert one of those around on the web.
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Old 09-30-2004, 04:08 PM   #4
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Radio Shack has books to help. They also sell some cheap power supplies. As for being a genius to construct one... If you can put your R/C car together, you can build a power supply.
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Old 09-30-2004, 04:21 PM   #5
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building a power supply isn't hard but getting the right transformer is. ya better off just buying 1
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Old 09-30-2004, 04:26 PM   #6
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yeah you can get a good power supply now for about $100 so it will save you a headace if you just drop the 100 and be done with it. but im sure if you wanted making one shouldnt be that hard
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Old 09-30-2004, 05:06 PM   #7
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Default try this

http://web2.murraystate.edu/andy.bat...owerSupply.htm
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Old 09-30-2004, 06:58 PM   #8
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I've done the PC power supply conversion and it is very easy. Just read the instructions and follow them to a T. You can save yourself a crapload of money by doing this. Works great, charges my batteries at 6A if I need it. Best of all it was salvaged and free.
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Old 09-30-2004, 07:36 PM   #9
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I've built my own Transformer-rectifier-regulator Power supply.
--heavy
Then I tried converting PC pwer supplies
--wimpy. Voltage drops below 11V on high loads

Now I'm happily using an Eagle 18 amp power supply.



Just go buy a commercial PWM supply. It will save you headaches plus it's easier to sell them when you need money compared to a homebuilt one.
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Old 09-30-2004, 10:29 PM   #10
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Quote:
Originally posted by rough512
I've built my own Transformer-rectifier-regulator Power supply.
--heavy
Then I tried converting PC pwer supplies
--wimpy. Voltage drops below 11V on high loads

Now I'm happily using an Eagle 18 amp power supply.



Just go buy a commercial PWM supply. It will save you headaches plus it's easier to sell them when you need money compared to a homebuilt one.
Actually the voltage drop is due to the fact you need to load the 5V bus to bump up the 12v bus. This is achieved via soldering resistor across the 5V bus. I've tried this experiment and it worked like a charm..... the 12V bus voltage increased from 10.5V to 12.5V. I have 2 made and charging at 6A is no big deal.

Bryan
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Old 09-30-2004, 10:31 PM   #11
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Quote:
Originally posted by donoman
.........Best of all it was salvaged and free.
Right on dude....saves us money for other stuff !!

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Old 10-01-2004, 07:29 PM   #12
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He's looking for a power supply to run his lathe. He doesn't mention charging so low voltage or amperage on the 12v side shouldn't be a problem.

I've got a couple of these and both work well.

The first one is an old 250w AT type. With 4 resistors (I'v forgotten the values) across the 5v tap I have enough power to run 2 chargers at 5a. The only problem is starting the second charger it goes into overload. Solved this by getting a big azz (beer can) size capacitor. The other problem is that certain chargers need a certain amount of over voltage to operate properly. My Tekin BC112 seems to need about 2.5v-3v over the batteries peak voltage to operate. If the battery peaks much over 10v it chokes and goes into low power error. My Novaks don't have this problem.

I got the second one to do just what Galactic wants, run my lathe. It's 155w ATX unit. It has 15a at 5v and 14a at 3.3v. Had no use for 12v in this one so I didn't install any resistors on the 5v tap. The 5v runs my lathe great and I use the 3.3v to break in my stock motors. It will also break in 19t motors if they don't need a lot of start up amperage. I don't think it will start up mod motors.

Best part is I got it from www.mpja.com for about 20 bucks. About 5 or 6 bucks for a switch and jacks an old computer cord and your in business.
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Old 12-03-2007, 11:58 AM   #13
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ok, so let me get this right...


the +12V 15A is going to give me a positive 12volts and 15amps. Which is what I need for my Duratrax ICE charger.

Wiring coming off an industry standard circuit board will be:



ORANGE +3.3 V
YELLOW +12 V
BLUE -12 V
RED +5 V
WHITE -5 V (May not be present on recently manufactured supplies)
BLACK GND
GREEN POWER-ON (Active high -- must be shorted to ground to force power up)
GRAY POWER-OK
PURPLE +5 V STANDBY
BROWN +3.3 V REMOTE SENSING

All I have to do is connect the black (GND) and the yellow (+12v) to my charger and I should be good to go. Being that I will be working with an ATX power supply I am going to need to ground the Green wire (POWER ON) to force it to turn on. And that is all? I will have a 12v 15a power supply?

thanks in advance!

Scott
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Old 12-03-2007, 12:14 PM   #14
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Quote:
Originally Posted by tornado View Post
Actually the voltage drop is due to the fact you need to load the 5V bus to bump up the 12v bus. This is achieved via soldering resistor across the 5V bus. I've tried this experiment and it worked like a charm..... the 12V bus voltage increased from 10.5V to 12.5V. I have 2 made and charging at 6A is no big deal.

Bryan
mmm iam experiencing sum problems with my 12v line aswell...when i conncet my ICE and start chargin and i can voltages anywhere from 10.7-11.7

can you tell us was resistance reisitor u used??

cheers

wog
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Old 12-03-2007, 08:55 PM   #15
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You can probably use a 3ohm resistor, 5-10 watt unit, could be had for about 25 cents at an electronics store, or a couple bucks at the source(radioshack). These are the large white resistors. As long as you got some load (1.5amps for say) out of the 5V line, the PS will crank out some current on the 12V line.

Even if the PS say 15A at 12V, don't get too happy!.. Most of these things don't put out as much current as they say it does. You either get a low voltage (voltage dips down to under 10V at a 5-7amp load despite a load on the 5V line) or it goes poof in a matter of seconds. They are cheap but not worth it in the long run....
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