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  #1  
Old Tue 15 September 2009, 08:41
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
Troubleshooting a DIY Power Supply

Okay guys i have an antek 600 watt powersupply... It has two outputs at 38 volts and basically thats what i need before the recitifier... Well this is how john at antek told me to hook it up.. I cant figure out why im get 76 volts double of the 38 and no multiplication of 1.44 after the recitifier.. How do i get the 38v and it multiplied by 1.44



Input:

Black and black to hot
Red and red to nuetral

Output: (the set for the 38v is one green and one blue)
Green and Green to one side of the recitifier
Blue and Blue to the other side...
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  #2  
Old Tue 15 September 2009, 09:03
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
OKay now i tried hooking one red and black together and one black to hot and one red to nuetral i get 36.8 volts green to green blue to blue and now the question remains how come im not getting the 1.44 mutiplication?
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  #3  
Old Tue 15 September 2009, 09:03
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Kyle, what is the part/model number of that supply?
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  #4  
Old Tue 15 September 2009, 10:14
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
You posted at the same time as me.

Looks like you purchased a transformer and not a power supply.

You need a capacitor after the rectifier before you will see the 1.41 (not 1.44) multiplication.
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  #5  
Old Tue 15 September 2009, 10:55
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Kyle,
Also don't forget that when reading the output of the transformer you should be using the AC mode of your meter. After the bridge rectifier and capacitor, use the DC mode of your meter.
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  #6  
Old Tue 15 September 2009, 16:15
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
After the recitifer i use V~ right? and i actually kinda thought about the capacitor being the problem but wasnt sure... And thank you i will hook everything up right away and tell you the results... and before the recitifier i cant seem to get a true reading its always 1 idk i might have my symbols mixed up...
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  #7  
Old Tue 15 September 2009, 17:10
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
Aww frick i forgot to put a resistor on the capactor... now it is charged at 54.7v what do i do?
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  #8  
Old Tue 15 September 2009, 18:12
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Lick your fingers and ... (No, don't do this).

V~ is usually a symbol for AC, so you would use that when measuring before the rectifier.

As for the capacitor, you could lay a resistor across the terminals to bleed it off.
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  #9  
Old Tue 15 September 2009, 20:01
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Or you could use a lamp pigtail and put in a 60 or 100W light bulb and use that to bleed off the charge. A pigtail is just a lamp socket with two leads coming off it. Works if you dont have any power resistors. Dont use a small wattage resistor, as that could flame on you if the value is low enough.
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  #10  
Old Tue 15 September 2009, 20:39
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
well when i test the voltage after the recitier i get 56v with the V~ and hmmm i guess when i test it with the other i get half that grr... im scared to hook up the wires the opposite way because if i do that then if it doubles my out put my capacitor wont handle it...
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  #11  
Old Wed 16 September 2009, 07:09
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Kyle,
It sounds like you have the wires correctly, as you stated you had 54V on the cap the other day. 38V AC on the transformer will give you 53.7V DC after the bridge and capacitor (approx). Leave the transformer wire like it is and if you have the bridge and cap hooked up and you are reading 54V or so on the cap DC then you are all set.
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  #12  
Old Wed 16 September 2009, 09:32
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Using pigtail lamps to drain capacitors . . . .

Heath, how about using a kettle, hairdryer, bedside lamp, anything with a standard plug on the end of the cord.......then touch the plug pins across the cap? The American plug has pins with about the right spacing. Our spacing is too wide.
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  #13  
Old Wed 16 September 2009, 12:40
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Gerald,
Any high wattage load as you suggested will work in a pinch. The spacing of the plug might not work for some types of capacitors (computer grade caps with screw terminals would be too wide). In that case it would be easy to use an old extension cord with one end cut off. Strip the wires and plug in the kettle / lamp etc and use the leads to connect to the capacitor.
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  #14  
Old Wed 16 September 2009, 16:11
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
Okay thank you guys... I actually got a pdf finally from antek about the transformer now im kinda worried... BUt first of all did i not have the symbol right for the voltage reader? i was using V~ at the capacitor to get 54ish volts and well here is the pdf i have it set up as 220... but does this really make a different because the way it is set up it is exactly the same just on two different sides of the transformer?

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  #15  
Old Wed 16 September 2009, 16:28
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
Also what size fuses should i put between my drivers and power supply?
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  #16  
Old Wed 16 September 2009, 19:31
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Kyle,
First off do you have any specs for the transformer?
What are the secondary voltages for the transformer?
What input voltage are you using?
You should be wiring the input side of the transformer for the input voltage you are using.
Now for the output side, I would wire it up as you have it in the second picture, 1 and 3 together and 2 and 4 together.
Use the V with the sin wave symbol to measure just the transformer wires (1/3) and (2/4) and make sure you have 38V AC before hooking up the rectifier and capacitor.
These wires (1/3) and (2/4) go to the ac input side of your rectifier.
The output side of the rectifier goes to the filter capacitor.
Use the V with bar (for DC measurement) to measure the DC voltage at the capacitor.
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  #17  
Old Wed 16 September 2009, 19:57
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Kyle, transformers work as the ratio of the number of turns on the input side to the number of turns on the output side. If you have ten turns on the input side, and ten on the output, you get the same voltage out (an "isolation transformer"). If you have ten on the input and five on the output, you get half the input voltage out. Ten in, twenty out would give you double, and so on.

How much power (amperage) you can draw out of a transformer is a function of the wire sizes used, and the size of the core.

Your transformer, per the PDF, has two input windings, and two output windings.
If you wire the input windings in parallel (red and red to neutral / black and black to hot), you provide more amperage, but the same input voltage. It's two input circuits, both with the same number of windings. If you wire the inputs in series (red to neutral, black to red, black to hot), you are doubling the amount of windings on the input side, which changes the ratio of input windings to output windings and halves the output voltage.

Similarly, on the output side, if you wire in parallel (green to green and blue to blue) you don't change the ratio. If you wire in series (green, green to blue, blue) you double the amount of windings on the output side, which doubles the output voltage.

So, I think what is happening here is that the natural ratio of your transformer is 115v to 38v, which is what you should get with red to neutral, black to hot, and then measuring green to blue (regardless of if you just use one set of each wires, or if you double them up in parallel). In your first test, you wired reds to neutral, blacks to hot, but then green, green to blue, blue, and you got double voltage at 76v for your
output. You then switched to red, red /black, black on your inputs, effectively halving your input, doubling your output, and getting the target of 38v. This will work, although it provides only half the current rating of the transformer.

What I think you want is at the top left and bottom right of the pdf page shown above, if it were rotated so that the text is normal: Red and Red to neutral, black and black to hot. Blue and blue to one side of your rectifier, and green and green and green to the other (these are the ~ pins of the rectifier).

Measure the output across the + and - pins of the rectifier and ensure you have something in the 38 to 50V range. If that is correct, then wire the + pin of the rectifier to + pin of your capacitor, - pin of the rectifier to - pin of your capacitor. Then you should see a nice, clean 54V-56V output across the + and - pins.

For your fuses, you want them just a little above the maximum expected draw from the driver. This is a function of whatever current you set your drivers to (using a resistor). For example, if you set the current limit for a motor to 3.5A, then you'll want something like a 4 or 5A fuse for the driver. I don't use discrete drivers, so I'll leave an exact recommendation to someone else.
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  #18  
Old Wed 16 September 2009, 20:11
shelbygt500buddy
Just call me: kyle
 
stuart fl
United States of America
Thanks brad i actually just got ballsy and did it its all parrell and it came out right. Thank you domino also and gerald... I just got my bob in today so hopefullly tomorrow ill get some thermal jell and get everythign in the case mounted and wired... I made my heatsink at work today... that was fun lol and also now that im heare i have a little 5v or w.e for my bob and it has ac in one 115 one 240 and one 50/60hz whats the 50/60 hz mean? and does it not need a nuetral? its a keling inc kl-10-5 i couldnt get any info on it.
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