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ATX to Lab Bench Power Supply Conversion
Thx for reply Matthew Currently.. my ATX power supply on yellow color wire output is 12v 20A I wonder it able to make it 13v 3A to charge deep cycle batterie
Hello Kokoro San. Be aware that many ATX power supplies have 12v split into 2 or more sub-supplies. Look at the sticker on the side of the ATX power supply for details. I would suggest using a battery charger to manage the charge process.I am not sure what you're asking about for diagrams?
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hi Matthewcurrently my ATX power supply have 12v with alot of Amps power...i wonder it can charge my deep cycle battery 12v 9A or parallel connection with 12v 54Ah. can you show us a diagrams that 12v have 1A , 2A, 5A , 10A ?-Kokoro San
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Hello, good question!Using Voltage = Current * Resistance, we know that 12 volts across a 25 ohm resistor results in 12/25=0.48 amps of current flowing through the resistor. The other important formula to use is Power = Voltage * Current, so 12 volts * 0.48 amps = 5.76 watts of power, that becomes heat in the resistor. Since the resistor is rated for 10 watts, you're not going to melt the resistor but it may get warm over time.I wouldn't expect it to get too hot to touch, so perhaps the resistor has less resistance, and is therefore drawing more current? If I remember correctly, the wirewound resistors that can handle many watts usually have a large variance in the amount of resistance it actually has, compared to the "official" resistance. If you have a multimeter you can measure the resistance of the resistor by itself, or you can put the meter in current measuring mode, and insert it in series with the resistor and measure the actual current. Let me know if you need more info about how to use a multimeter for this kind of investigation.If you could find a 100 ohm power resistor, that might work better. It would result in 0.12 amps of current instead of 0.48 amps. I really don't know how much current is needed for the minimum load, but I would guess that 0.1 amps would be enough. This would reduce the power burned as heat in the resistor down to 1.44 watts, so you could use a 5 watt power resistor instead of 10 watt.
have soldered a 25ohm 10watt resistor on my 12 volt rail since it has the most power.but the resistor is getting too hot that i can't touch for long... is that normal? do i need to use a heatsink? or something else? please help..
Hello, good question! If you want to limit a specific binding post to only output a certain amount of current (1A, 2A, 5A, etc) then you need to use a fuse that will blow when the current limit is exceeded. Be aware that fuses are not very precise in terms of current limits, and there is usually a range where the fuse may or may not blow.Hope that helps, let me know if you have further questions, or if I didn't understand what you were asking.-Matthew
if i want to put more binding post do add more specific current for my 5volts and 12 volts (like 1A, 2A, 5A) what should i do? thanks..
Thanks alot, here's my version. Converted from an old 250W Hipro unit from my mother's ancient Pentium 4 machine that just finally gave up last month.
TheLonesometoad, I was having the very same problem you were, but I was able to resolve it using two 10Ω resistors in parallel, on the 5v line. This gives me an equivalent resistance of 5Ω, and it seems that is enough for my power supply. I got the idea for this from matthewbeckler's reply to harshesh below. Hope this helps!
Lol my power supply is anything but new, I think. When I bought it the fan grill was completely covered in dust and I mean like a thick layer of it. But yeah I guess it varys with PSU. Also those aren't 7 segment displays its just a cheap 3 digit voltage meter, you can buy them in ebay.
Thanks for the instructable it helped me a lot with my PSU. One thing you forgot to mention, or it didn't apply to you, was that you have to connect the 3.3V brown sense wire to the 3.3V rail or else the unit wont turn on. Idk if this apply's to everyone but my unit would only turn on for a second then turn off when it wasn't connected. Also added a LM2596 buck converter in my unit so I can have a adjustable voltage output. I also used 5x 15Ohm 1 Watt resistors in parrell to get a comparable 5W resistor then I used another bundle of those 15Ohm 1Watt resistors and added it in series to have a total of around 10W at about 6Ohms.
Hmm... That looks more like a sun chip
Encyclopedia of ATX to Bench Power Supply Conversion
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