I am trying to convert a PSU (pc power supply) to a bench top power supply there is one point that I do not understand, that is the wire that is labeled 3.3 sense. If you know what the 3.3 sense wire does please let me know.
Thanks
AIDayley
View attachment 118625

 

That wire feeds the 3.3V back to the power supply to regulate the voltage at the point where it is connected to the 3.3V rail. This compensates for the voltage drop along the supply cables (3.3V is a high current supply).

 

What will I do with it when I turn it into a bench top power supply.

 

Connect it to the 3.3V supply output.

 

Thanks for the help
AIDayley

 

I am trying to convert a PSU (pc power supply) to a bench top power supply there is one point that I do not understand, that is the wire that is labeled 3.3 sense. If you know what the 3.3 sense wire does please let me know.
Thanks
AIDayley
View attachment 118625

You have to be a bit careful!

When I serviced them for a living, I encountered a cheap low spec ATX PSU with the 3.3 sense on its own with a pin to itself. My home made dummy load just picked up a connection to each rail and didn't link all the same rail pins like the trace on a motherboard does. With nothing fed back on the 3.3 sense line; the SMPSU circuit went flat out trying to get the sense line up - the PSU want bang.

Usually the sense wire is crimped into a pin alongside a rail feed wire - if it isn't; connect it yourself.