Hi All,

I have a strange one with a circuit I'm currently building. I've got everything working fine but this is when the circuit is connected to a 9v battery supply. I've added a DC barrel jack so I can power it from the mains through a 9v PSU but when I connect this at the same point it doesn't work. The lead shows approx 9v but when I connect it up it shows around 0.7v on the board. I don't know if it could have something to do with the diode but I'm not sure.

I have attached a photo to show how I have wired it up. I've also got the battery running through the switch in the jack but that doesn't work when its unplugged. The red and black are the battery pack.

If anybody has any ideas I would be grateful

Thanks

 

What’s the function of the diode?
Also, use your multimeter to double check the polarity of the PSU vs the battery.
Finally, it’s possible your PSU can’t handle the current requirements and the voltage collapses.

 

What’s the function of the diode?
Also, use your multimeter to double check the polarity of the PSU vs the battery.
Finally, it’s possible your PSU can’t handle the current requirements and the voltage collapses.

Absolute legend, thank you. It was the polarity of the PSU

 

The contacts in the socket disconnect the negative side of the battery. The battery negative should be connected to the the tag marked plug detect in your picture. (Not directly to the to the anode of the shunt polarity protection diode.) The battery positive connects directly to the cathode of the shunt polarity protection diode.
Les.

 

The contacts in the socket disconnect the negative side of the battery. The battery negative should be connected to the the tag marked plug detect in your picture. (Not directly to the to the anode of the shunt polarity protection diode.) The battery positive connects directly to the cathode of the shunt polarity protection diode.
Les.

This configuration doesn't seem work it this case. Potentially due to the polarity . The plug detect pin would be connected to the +ve sleeve therefore would connect to the cathode from the "ground" pin in this case. Then -ve of battery to the diode anode.

 

I was assuming that you were using the centre pin as positive (The most common polarity for thes plugs.) and that the polarity protect diode was connected across the supply so it blows the fuse in the power supply if the polarity is wrong..
Please post a schematic of how you want it wired.. (Not a picture of your construction) .

Les.