Help to identify PSU voltage sense-wires

[RasmusEu]

I'm planning to make a set of very short 17 AWG PSU cables for my SFF build. The voltage-sense wires will not be needed. I have seen people either completly leaving them out or using small jumper cables on the PSU side. I'm hoping my PSU (Corsair SF450) will accept leaving the cables out.

 

But how do I identify which pin on my PSU is for carrying the current and sensing the voltage? I have made my own PSU-pinout. For example, I want to identify and distinguish terminal 10 (+12 V) on the PSU side.

 

Thank you.

[W-L]

12 hours ago, RasmusEu said:

I'm planning to make a set of very short 17 AWG PSU cables for my SFF build. The voltage-sense wires will not be needed. I have seen people either completly leaving them out or using small jumper cables on the PSU side. I'm hoping my PSU (Corsair SF450) will accept leaving the cables out.

 

But how do I identify which pin on my PSU is for carrying the current and sensing the voltage? I have made my own PSU-pinout. For example, I want to identify and distinguish terminal 10 (+12 V) on the PSU side.

 

Thank you.

 

You'll need to verify with the original cables and check which pins have a dual connection and what pins they would go to, usually the thinner wire is for sense. If you disconnect one of the lines you should be able to probe and measure which one is providing the 12V supply, as the sense itself shouldn't be outputing a voltage from my understanding. Depending on the PSU some will not be happy without signal/sense feedback so that will need to be tested. 

[leham]

There is PWR_OK and 3.3v Sense

 

PWR_OK is pulled high to 5V (5VSB [standby, usually purple wire] not 5VDC [higher current rail, red wire])

 

Sense is also pulled high but to 3.3v (orange wire)

 

 

Some modern power supplies tie PWR_OK to 5V+SB and sense to 3.3v internally, others don't.

 

Every psu I've jumped for projects, I've just needed to pull PS_ON (green wire) low (to ground).

[RasmusEu]

On 3/13/2020 at 6:21 AM, W-L said:

You'll need to verify with the original cables and check which pins have a dual connection and what pins they would go to, usually the thinner wire is for sense. If you disconnect one of the lines you should be able to probe and measure which one is providing the 12V supply, as the sense itself shouldn't be outputing a voltage from my understanding. Depending on the PSU some will not be happy without signal/sense feedback so that will need to be tested. 

Pin 13, 19, 21 and 10 are double wires.

The cable thickness is identical for both the current carrying wire and voltage sense wire.

 

Pin 13 measurements and tests:
+3.3V

Both wires output +3.3V from the PSU side to the device side

Did the voltage change when unplugging one of the double wires (testet for both)? NO
Power good test (one double wire unplugged): OK measured 5V
Power continuity test (between pin16 and GND): OK

 

Pin 19 measurements and tests:
0V

Both wires are connected to GND from the PSU side to the device side

Did the voltage change when unplugging one of the double wires (testet for both)? NO
Power good test (one double wire unplugged): OK measured 5V
Power continuity test (between pin16 and GND): OK

 

Pin 21 measurements and tests:
+5V

Both wires output +5V from the PSU side to the device side

Did the voltage change when unplugging one of the double wires (testet for both)? NO
Power good test (one double wire unplugged): OK measured 5V
Power continuity test (between pin16 and GND): OK

 

Pin 10 measurements and tests:
+12V

Both wires output +12V from the PSU side to the device side

Did the voltage change when unplugging one of the double wires (testet for both)? NO
Power good test (one double wire unplugged): OK measured 5V
Power continuity test (between pin16 and GND): OK

 

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Conclusion: I still haven't figured it out.

 

I could put my multimeter in series with one of the double wires one at a time and check the amp draw.

 

Or would it be safe to unplug one of the double wires and just observe if my PC turns on?

 

[W-L]

3 hours ago, RasmusEu said:

-SNIP-

 

A multimeter in series or ideally a clamp meter capable of lower amperages should let you determine which one is sense and the main current draw. As for disconnecting it depends on how the PSU reacts some will not turn on or shut down if the sense line is disconnected while others will not have and issue running without it. From what I've tried before it usually doesn't turn on the PSU if you disconnect the sense line. 

 

If you jumped the line on the PSU side with a short wire then lead out to the 24 pin that shouldn't have a problem given that your jumper wire and the one going to the 24 pin is the same size and not super thin. 

[RasmusEu]

On 4/7/2020 at 3:17 PM, W-L said:

A multimeter in series or ideally a clamp meter capable of lower amperages should let you determine which one is sense and the main current draw. As for disconnecting it depends on how the PSU reacts some will not turn on or shut down if the sense line is disconnected while others will not have and issue running without it. From what I've tried before it usually doesn't turn on the PSU if you disconnect the sense line. 

 

If you jumped the line on the PSU side with a short wire then lead out to the 24 pin that shouldn't have a problem given that your jumper wire and the one going to the 24 pin is the same size and not super thin. 

I measured pin 13, 19, 21 and 10 and finally managed to identify the voltage sense wires.

My computer is working perfectly fine without all 4 sense wires for my motherboard.

However my PC won't continue to boot without the voltage sense wires for my GPU. I will just get the messege: "Please power down and connect the PCIe power cable(s) for all graphics cards". I used a small jumper cable and solved it.

[W-L]

17 minutes ago, RasmusEu said:

I measured pin 13, 19, 21 and 10 and finally managed to identify the voltage sense wires.

My computer is working perfectly fine without all 4 sense wires for my motherboard.

However my PC won't continue to boot without the voltage sense wires for my GPU. I will just get the messege: "Please power down and connect the PCIe power cable(s) for all graphics cards". I used a small jumper cable and solved it.

If it's not in the way I'd leave the sense wires in place using a short jumper on the PSU side as having feedback isn't a bad thing for the system. The 12V rail is usually the most important and can go under sudden changes in load much more rapidly which is at least my presumption why it might require it. 

 

When I repined and sleeved an AX series from Corsair (seasonic) it wouldn't turn on without all the sense cables connected. 

[eliar]

On 4/8/2020 at 1:45 PM, RasmusEu said:

I measured pin 13, 19, 21 and 10 and finally managed to identify the voltage sense wires.

My computer is working perfectly fine without all 4 sense wires for my motherboard.

However my PC won't continue to boot without the voltage sense wires for my GPU. I will just get the messege: "Please power down and connect the PCIe power cable(s) for all graphics cards". I used a small jumper cable and solved it.

 Wow you're a life saver. I have an SF600 and been wondering how to determine which wire is the sense wire since they will both have a voltage across them. This makes my sleeving so much easier to do.