Circuit board marking

Thread Starter

Usbuild

Joined Apr 20, 2019
2
I’m trying to figure out what is -S, +S and PS could stand for?
I checked voltage on PS, it’s 0.05vdc when idling and 0.2vdc when 10Amp load applied on 12V rail.
I didn’t attempt to test S terminals, as I have no clue what it could be and how to safely test it.

What I’m trying to accomplish:
I would like to add a switch on low voltage side and control it with ESP-12E board
My assumptions are S stands for switch, 5V rail is always On and 12V rail can be switched On/Off.

There is no schematic available for this PSU (well, i coudnt find one). It’s made by Skynet Electronics, model PEL-R307. PEL probably stands for Pelco. There was two of these PSUs in rack mountable shelf. I’m assuming for redundancy.
100-240V 50-60Hz 4A
12Vdc 21A
5Vdc 0.1A





E8C16E97-1A40-465D-A573-8410BACCA620.jpeg D18D1993-6BAA-478B-89D1-47FDA0142AAC.jpeg
 

MrChips

Joined Oct 2, 2009
21,041
Does the power supply provide the proper +5V and +12V output when AC power is applied?

+S and -S would normally be used for remote sensing.
+S would be connected at the load +V supply.
-S would be connected at the load GND return.
Without specific information, I can only guess that this refers to the +12VDC 21A supply.
I don't know what PS means. I would guess that PS means Power Status to indicate that the power is on.
 

AnalogKid

Joined Aug 1, 2013
8,438
S+ and S- probably are remote sense connections. 21 A is a large enough amount of current that there can be a measurable voltage drop in the wires going out to the load, decreasing the apparent load regulation. With remote sense, you run a second wire pair (thinner wire) out to the load. In this way, the supply's error amplifier is detectin the actual voltage at the load, not at the output terminals, and the supply's control loop increases the output voltage at the terminals to compensate.

Since the connector is not populated, there is a good chance that the rest of the components necessary to implement remote sensing are not installed either. It is common for a single pc board to be used for different models, output voltages, extra features, etc.

The manual for the supply might state that the remote sense connections should be tied to the main output terminals, but usually the connector is populated if that is required.

Does the output come up and regulate with a light load? A common requirement for this type of switcher is a 10% minimum load; 2.1 A in your case. If the supply regulates ok, measure the voltage between S+ and +Vout, and S- and -Vout. If those are remote sense connections, they should be very close to 0 V.

ak
 

Thread Starter

Usbuild

Joined Apr 20, 2019
2
Does the power supply provide the proper +5V and +12V output when AC power is applied?
It does. 5.1V and 12.36 when idling, 12.2 at 10A load
+S and -S would normally be used for remote sensing.
+S would be connected at the load +V supply.
-S would be connected at the load GND return.
Indeed, I’m measuring 12V on S terminals

There is about 3 seconds delay between applying power and output. That’s one of the reasons I wanted to keep it constantly On and switch 12V rail.
I’ve done something similar with standard PC PSU. But I guess it’s not possible with this unit
 

MrChips

Joined Oct 2, 2009
21,041
Then it means that +S and -S are not being used. They are probably jumpered internally to +12VDC and GND.
You can ignore these.
 
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