What type of resistor is needed for a dummy load on a 350W PC PSU?

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Discussion Overview

The discussion revolves around the requirements for creating a dummy load for a 350W PC power supply unit (PSU) with multiple voltage outputs (3.3V, 5V, and 12V). Participants explore the specifications of resistors needed for proper operation and the configuration for connecting these loads.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests using a 10 ohm, 10W resistor for the dummy load and questions whether a separate resistor is needed for each voltage output or if one can be used across the 5V output.
  • Another participant notes that PC power supplies often have minimum output current requirements for certain rails and advises checking the datasheet for these specifications.
  • A later reply mentions that many PSUs require a Power On line to be grounded for the unit to operate, suggesting that grounding this line could allow the PSU to start and supply all outputs.
  • A participant reports successfully installing a 6.8 ohm, 10W resistor connected to the 5V output, indicating that the PSU operates correctly when switched on and off using the Power On line.

Areas of Agreement / Disagreement

Participants generally agree on the need for a dummy load and the importance of grounding the Power On line, but there is no consensus on the exact resistor configuration needed for each output voltage.

Contextual Notes

There are mentions of minimum output current requirements and the necessity of grounding the Power On line, but specific details on these requirements are not fully explored in the discussion.

Glenn Borg
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Hi,
I have a 350 w PSU (PC) with 3.3, 5 and 12 v outputs.

I want to create a dummy load so that i will remain on and output the correct voltage.

However, i found online that a 10 ohm 10w resistor is needed such as this one :
http://www.fabian.com.mt/en/product...tor-wirewound-aluminium-housed-10-ohm-10w.htm

Can you kindly verify if i need one for every output ? (3.3, 5 and 12 v)
Or i connect one end to a Positive 5v and on the other end ground and still can use all outputs ?

Thanks
 
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Glenn Borg said:
Hi,
I have a 350 w PSU (PC) with 3.3, 5 and 12 v outputs.

I want to create a dummy load so that i will remain on and output the correct voltage.

However, i found online that a 10 ohm 10w resistor is needed such as this one :
http://www.fabian.com.mt/en/product...tor-wirewound-aluminium-housed-10-ohm-10w.htm

Can you kindly verify if i need one for every output ? (3.3, 5 and 12 v)
Or i connect one end to a Positive 5v and on the other end ground and still can use all outputs ?

Thanks
PC power supplies often have a minimum output current on one or more of the rails. The datasheet for the power supply should specify those minimum output currents -- have you checked for that yet?
 
Glenn Borg said:
Can you kindly verify if i need one for every output ? (3.3, 5 and 12 v)
Or i connect one end to a Positive 5v and on the other end ground and still can use all outputs ?

berkeman said:
PC power supplies often have a minimum output current on one or more of the rails. The datasheet for the power supply should specify those minimum output currents -- have you checked for that yet?

agree with Berkeman, there are those that are like that
and a large majority have a Power On line that needs to be grounded before the PSU will start up and run

ATX power pins.JPG


just permanently ground the Power On line and the PSU should always start up and supply all railsDave
 
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Thanks a lot for the answers, i have managed to install a resistor (6.8 ohms 10w) connected to a 5v output. managed to turn on with a switch on the green wire and ground. so far so good, switches on and off accordingly. Thanks
 
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Likes   Reactions: davenn and berkeman

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