Hello im David a newbie on this platform. I connected a molex cable on a regulated dc power supply in one direction and power just flew in through the Molex cable as it is suppoesd to be and. Again i changed the polarities and it just switched off the base station as a sign of warning to the base station that its a short . My question is how does that happen. Since its just a cable it is supposed. To just conduct not to be polarised.

 

hi David,
Welcome to AAC.
How many pins on the Molex connector.?
What is connected to the wires of the Molex.? [what device is the PSU powering]
E

 

I sounds like the item you are supplying power to has a reverse polarity protection diode between positive and negative. The diode may now have failed short circuit or it may have failed short circuit at first and then was blow open circuit if enough current was available. You should give more details of your problem if you want and answer that is better than just a wild guess.

Les.

 

Its a 2pin molex cable ,it is. Powerd to a PSU of 48volts and.its powering. A DC PCB connected to a certain control station. I guess if i may answer

 

Why did you reverse the polarity?

 

I sounds like the item you are supplying power to has a reverse polarity protection diode between positive and negative. The diode may now have failed short circuit or it may have failed short circuit at first and then was blow open circuit if enough current was available. You should give more details of your problem if you want and answer that is better than just a wild guess.

Les.

Yeah thats true but my qiestion is on theMolex cable functionality how does it have polarity. I guess if its a cable it just has to conduct in any polarity

 

The fact that the cable conducts any polarity is the answer to your query, it is the connector that determines the correct polarity.

The Molex connector usually has a mechanical feature that makes it non reverse-able.
E

 

That is a 4 pin connector but only 2 pins are used. looking at your out of focus picture it looks like it is only possible to insert it one way. Did you manage to insert it 180 degrees from it's correct position or 90 degrees in one direction from it's correct position. If there are also only 2 pins in the mating connector then nothing should have been damaged. (Other than the connector moulding by using excessive force to insert it the wrong way.)

Les.

 

The fact that the cable conducts any polarity is the answer to your query, it is the connector that determines the correct polarity.

The Molex connector usually has a mechanical feature that makes it non reverse-able.
E

Exactly my point is how does a connector determines polarity. I think that if it is composed of wires only then. It cant have the capability of determining the polarity.

 

The connector is not composed of wires, its the connector body shape that should prevent you from inserting it in the wrong way.
Post a clear image of the connector.
E

 

Note that the "shrouds" over the pins in the connectors have different shapes. They have to go into receptacles of the same shape. That gives the connector a polarity.

 

Ok let me. Explain well my query. I was building a molex cable. To put into my pcb and at the end of the molex cable i used banana plugs (red =positive and black=negative). But when building my molex cable i had inversed the banana plugs on the reverse direction at first . I connected. It into the UPS using a spliter and the other end.(molex cable end par)into my PCB and the control station as a security measure it shutdown power. Meaning that that was the revese direction and again i switched the banana plugs on the cables and it worked.

Basically my question is if molex cable is just a cable meaning that it has no polarity. Why did it cause the station shutdown. The problem is not at the input of molex to the board but at the banana end points.

 

Hello im David a newbie on this platform. I connected a molex cable on a regulated dc power supply in one direction and power just flew in through the Molex cable as it is suppoesd to be and. Again i changed the polarities and it just switched off the base station as a sign of warning to the base station that its a short . My question is how does that happen. Since its just a cable it is supposed. To just conduct not to be polarised.

The answer is:
When you changed the polarities, you connected the positive output of the supply to the negative input of your PCB and the negative output of the supply to the positive input of the PCB which shorted out the supply.
The wires will conduct in either direction (not polarised as you mentioned) but your PCB draws too much current for the supply to handle when it is connected in reverse polarity.