DC Barrel Jack Sparking

[JoeWawaw]

Hi, I'm using a DC barrel jack in a SMPS circuit, and whenever I plug in the jack, small sparks can be seen. The SMPS circuit if is shutdown mode during power on, so I'm thinking the input caps i have (2x 10uF ceramic, and 100uF aluminum) are causing the sparks.
Since i cant remove those caps as they are essential to the SMPS circuit, how could i eliminate these sparks?
I'm using a barrel jack like this one: https://www.sparkfun.com/products/119

 

[MikeMl]

What is pin 3 (see the Sparkfun datasheet link) connected to?

 

[JoeWawaw]

So pin 3 (the center one) is V+, pin 2 is GND, and pin 1 is unconnected

 

[MrAl]

Hello,

Maybe an input surge suppressor. Goes in series with the input.

One of my battery chargers does that too, and i was thinking about doing the same.

 

[Inquisitive]

Like this.



In this case the center pin just happens to be #1 but (+) positive

 

[MikeMl]

So pin 3 (the center one) is V+, pin 2 is GND, and pin 1 is unconnected

Go look at the linked data sheet again. The center pin is pin 1. The thing that connects the outside of the plug is pin 2, and pin 3 is the switched contact, which is opened when the plug is inserted...

 

[JoeWawaw]

ahaha i guess i got my pinout wrong, but on my circuit it is correct
MrAI, what would the circuit look like?
My input is 12VDC, and during operation it can pull up to 5A

 

[Les Jones]

Hi Joe,
Have you noticed that it is only rated at 2.5 amps. (From the data sheet from your link.)

Les.

 

[JoeWawaw]

The one i'm using is from digikey, and its rated for 5A
i took sparkfun's for illustration

 

[ChrisP58]

The simplest is a resistor between the connector and the cap. But the resistor will have a voltage drop during operation, so add a timer and a relay to bypass the resistor after a short delay.

 

[chemelec]

Besides seeing the Spark, Is it causing any problems?
If not, I would just leave it as is.

 

[JoeWawaw]

The spark isnt affecting my circuit at all, but im concerned about safety issues if the circuit were to be mass produced
Which of the caps i have placed (2x10uF ceramic, or 100uF aluminum) would be causing the problem? I'll try desoldering it to confirm for sure that its causing the sparking

 

[MrAl]

ahaha i guess i got my pinout wrong, but on my circuit it is correct
MrAI, what would the circuit look like?
My input is 12VDC, and during operation it can pull up to 5A

For example the ICL:
https://media.digikey.com/pdf/Data Sheets/Ametherm PDFs/SURGE-GARD_Series_Web.pdf

You can look for a suitably rated part.
The device goes in series with your power supply input lead. The resistance can change 50 fold so if it starts out as say 10 ohms it can go down as low as 0.2 ohms once the current starts to flow.

Current limiting is rather strange for apps like this because you have a sudden capacitor to capacitor connection, and without any series resistance it creates a short duration but high current peak. The current will be limited by the dynamic resistance, but for a fixed resistance of 1 ohm and 12 volts the current peak is 12 amps, and for 2 ohms and 12v it is 6 amps, and for 10 ohms and 12 volts it is 1.2 amps, etc., etc. As the ICL changes resistance it allows the cap to charge up slowly and then allow the circuit to work normally with little loss.

There is a chance that a fixed series resistor might work too if the app can tolerate the voltage drop.

 

[chemelec]

Have you measured the Voltage Difference between the two devices?

Are Both Device Line Operated and do both have Grounded Plugs?

 

[spec]

Hi, I'm using a DC barrel jack in a SMPS circuit, and whenever I plug in the jack, small sparks can be seen. The SMPS circuit if is shutdown mode during power on, so I'm thinking the input caps i have (2x 10uF ceramic, and 100uF aluminum) are causing the sparks.
Since i cant remove those caps as they are essential to the SMPS circuit, how could i eliminate these sparks?
I'm using a barrel jack like this one: https://www.sparkfun.com/products/119

Hi Joe,

How much, if any, electronics would you be able/prepared to fit at either the plug or socket end. Or maybe a little interface box. If that were acceptable, I think a solution to your problem would be pretty straight forward- a MOSFET and a few passive components should do it, without generating any heat. I'm just thinking out loud at the moment.

 

[JoeWawaw]

Hi guys,
thanks for your replies, after some thought i decided to not do anything about the sparking

 

[spec]

Hi Joe,

Good call

spec

 

[MrAl]

Hello again,

I should have also mentioned that when using an inrush current limiter NTC thermistor the device has to be allowed to get pretty hot in order to work correctly. The resistance comes down with temperature but to see a marked change in resistance the temperature has to be allowed to get pretty high, possibly around 170 degrees C.
I have a device that is around 2.5 ohms at 25 deg C, but even at 5 amps it's resistance only comes down to maybe 0.5 ohms. That's might not be enough of a change for example.

 

[kinarfi]

A resistor between terminals 1 & 2 would discharge the cap and when disconnected and drop out of the circuit when plug is inserted.
When you insert the plug, is the power on or off, is the plug power into or power out from the SMPS

 

[kinarfi]

2 more cents, If the jack is the power input to the SMPS, #2 & #3 would act as soft starts