Dummy load for an ATX power supply upgrade !

[Charybdis]

Hi there, I'm following the amazing tutorial from this guy:


And he said to use a dummy load of 10ohm  10W to make stable the PS output.
I'm still finishing this project (since 4 years  )

but I made a quick continuity check with my multimeter and it BEEPS when it comes to 5V rail and GND. Is it right to say that if I would have switched on this PS it would have get fried ? I assume the 6,8 Ohm 11W resistor I had it's not enough right? How can I choose wisely a resistor to make a dummy load without frying everything?
Thank you

[james_s]

Most continuity modes beep whenever there is less than about 50 Ohms so this is not surprising. Use Ohms law to calculate the draw of your load, 6.8 Ohms, 5 Volts, it is trivial to calculate exactly how much current it will draw and how much power it will dissipate.

[ogden]

I assume the 6,8 Ohm 11W resistor I had it's not enough right?

Anything in 5..10 Ohms range is OK as idle load for 5V rail of ATX supply. Place your 6.8 Ohm resistor into the air flow and you will be fine.

[Charybdis]

Anything in 5..10 Ohms range is OK as idle load for 5V rail of ATX supply. Place your 6.8 Ohm resistor into the air flow and you will be fine.

Thank you Ogden, so how can I understand if I will make a shortcircuit or not?
I thought 5Ohm were not enough to prevent a shortcircuit.

Most continuity modes beep whenever there is less than about 50 Ohms so this is not surprising. Use Ohms law to calculate the draw of your load, 6.8 Ohms, 5 Volts, it is trivial to calculate exactly how much current it will draw and how much power it will dissipate.

Well actually I was more concerned by a possible shortcircuit, but thanks I didn't know about the 50 Ohm thing

[james_s]

A short circuit is 0 Ohms, you cannot create a short circuit by connecting a resistor across.

I told you everything you need to know to calculate the amount of power any resistor will draw, use Ohms law, look it up if you're not familiar with it, you will use it constantly doing any sort of electronics work. Once you calculate the current, compare that to the current the power supply is rated to deliver, and calculate the power and compare that to the wattage rating of the resistor.

[Charybdis]

A short circuit is 0 Ohms, you cannot create a short circuit by connecting a resistor across.

I told you everything you need to know to calculate the amount of power any resistor will draw, use Ohms law, look it up if you're not familiar with it, you will use it constantly doing any sort of electronics work. Once you calculate the current, compare that to the current the power supply is rated to deliver, and calculate the power and compare that to the wattage rating of the resistor.

OK I think I got it.
The current through the resistor should be 0.73A while the wattage that the 11W resistor will handle will be 3.65W. So it should be perfectly fine right ?
Thank you