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PSU HAA15-0.8-AG extra sense pins?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author PSU HAA15-0.8-AG extra sense pins?
mmeixner
Hi!

I just bought three HAA15-0.8-AG PSUs, and I'm wondering about the pinout:




+OUT/-OUT/COM and the outer sense pins +S/-S are clear. But whats the point of the +S/-S connections in the bracket in the middle? Obviously they are connected to COM, if testing for continuity, but why are they called +S/-S? Seems unintuitive to me ... or am I overlooking something?
BananaPlug
Keep looking there are other threads (and PSU's manual's) with very good detailed explanations etc.

The short story is that it's a way to compensate between voltage loss over a long cable between the PSU and you load.
Dofkev
Here is a thread where this is discussed, some good advise graphics from Dave Jones:

https://www.muffwiggler.com/forum/viewtopic.php?t=66924&start=all&post days=0&postorder=asc&sid=1140fd605fbc810a739e316127eab837



Graham Hinton
mmeixner wrote:
+OUT/-OUT/COM and the outer sense pins +S/-S are clear. But whats the point of the +S/-S connections in the bracket in the middle? Obviously they are connected to COM, if testing for continuity, but why are they called +S/-S? Seems unintuitive to me ... or am I overlooking something?


All PSUs with remote sensing are the similar. Each rail has a pair of sense inputs that are connected between the rail and 0V at the point that needs to be regulated.



Note my terminology is slightly different to avoid duplicate names, they should be obvious from the order and PSUs are usually laid out to make local sensing a straightforward connection.

Remote sensing may be used to counteract the voltage drops in long cables, but be aware of these points:
1) The actual adjustment range may be limited, if you need to compensate for over a volt drop you are doing something wrong.
2) The sense wires modulate the output and so may need to be a twisted pair and or screened. Microphone cable is suitable
3) The sense wires don't carry heavy current and if used the rail cables don't have to be so thick, depending on length.
4) Do not ground the Com output, rather connect mains Earth to the distribution 0V. There is a current in the Com wire equal to the difference between the +ve and -ve currents, so unless these are exactly equal there is usually a voltage drop.
mmeixner
Graham Hinton wrote:
mmeixner wrote:
+OUT/-OUT/COM and the outer sense pins +S/-S are clear. But whats the point of the +S/-S connections in the bracket in the middle? Obviously they are connected to COM, if testing for continuity, but why are they called +S/-S? Seems unintuitive to me ... or am I overlooking something?


All PSUs with remote sensing are the similar. Each rail has a pair of sense inputs that are connected between the rail and 0V at the point that needs to be regulated.



Note my terminology is slightly different to avoid duplicate names, they should be obvious from the order and PSUs are usually laid out to make local sensing a straightforward connection.

Remote sensing may be used to counteract the voltage drops in long cables, but be aware of these points:
1) The actual adjustment range may be limited, if you need to compensate for over a volt drop you are doing something wrong.
2) The sense wires modulate the output and so may need to be a twisted pair and or screened. Microphone cable is suitable
3) The sense wires don't carry heavy current and if used the rail cables don't have to be so thick, depending on length.
4) Do not ground the Com output, rather connect mains Earth to the distribution 0V. There is a current in the Com wire equal to the difference between the +ve and -ve currents, so unless these are exactly equal there is usually a voltage drop.



Thanks all!
I'm familiar with the concept of sensing, I was just unsure about the pin naming and arrangement and wanted to make sure (the data sheet does indeed clarify the concept but didn't tell about the layout of the connections).

Thanks Graham especially for the very clear descriptions - as always!
fuzzbass
mmeixner wrote:
Thanks all!
I'm familiar with the concept of sensing, I was just unsure about the pin naming and arrangement and wanted to make sure (the data sheet does indeed clarify the concept but didn't tell about the layout of the connections).

Thanks Graham especially for the very clear descriptions - as always!


Also don't forget to pull the VW1 and VW2 jumpers off if you need +/-15V operation.
Rex Coil 7
Graham Hinton wrote:
... 2) The sense wires modulate the output and so may need to be a twisted pair and or screened. Microphone cable is suitable.
(I highlighted) ... Shield (*screen) to chassis?
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