Removing generated sparks

Hi,

Could "agu car audio on/off fuse and breaker" be used to reduce/remove generated sparks?

Thanks

maatthew:
Hi,

Could "agu car audio on/off fuse and breaker" be used to reduce/remove generated sparks?

Thanks

What is that thing you mention and where are you seeing the sparks?
Paul

I am not sure what you are asking but I will take a SWAG. I assume it is generator or alternator noise you hear in the audio of the radio. If so check with your local automotive supplier they sell the suppressors for a minimal price. They are generally an inductor, some with capacitors. They also sell them for Ignition noise as well.

Hi,
We need more information.

  • What voltage is causing the sparks?
  • What is the current?
  • AC or DC current?
  • Sparks across what and when?
  • What is the load that you are controlling?

Thanks… Tom… :slight_smile:

Post a photo of the 'sparks'

Thanks for your inputs.

There is a robot, which uses 36v battery (4400mAh)

When I am trying to connect the battery, I see the spark.
I assume by putting a simple switch It will be still there, but can not be seen.

So what I am trying to do is to remove that spark.

photo:

spark.png

spark.png

The sparks are the arcing due to current inrush.
Even a switch would arc internally. Only a semiconductor device like a mosfet would prevent it.

If the sparking is due to charging a large capacitor, you could connect a suitable resistor between battery and robot until the cap is fully charged and then make the direct connection without the resistor.

It is probably current inrush due to connecting a low internal resistance battery to a high current load. The electrons can jump the gap faster than
you can connect the plug.

raschemmel:
The sparks are the arcing due to current inrush.
Even a switch would arc internally. Only a semiconductor device like a mosfet would prevent it.

Thanks

I was wondering if you could help me by providing related keywords that I could search or maybe a schematic that could shed light, because I couldn't find anything online.

I appreciate it.

herbschwarz:
If the sparking is due to charging a large capacitor, you could connect a suitable resistor between battery and robot until the cap is fully charged and then make the direct connection without the resistor.

Thanks, this sounds a little manual which right now I don't think I am intent to pick this route.

Thanks, this sounds a little manual which right now I don't think I am intent to pick this route.

If the sparking is due to charging a large capacitor, you could connect a suitable resistor between battery and robot until the cap is fully charged and then make the direct connection without the resistor.

Not if you know electronics.
This is a simple and straight forward uP controlled relay application.

At a company I worked at once they had a huge resistor bank and when you pushed
the button to turn the the equipment it energized a time delay relay that engaged a contactor connecting the current inrush resistor bank. Two seconds later the relay timed out disconnecting the resistor bank and energizing
a second relay that had a 3 second delay before engaging the equipment.

raschemmel:
At a company I worked at once they had a huge resistor bank and when you pushed
the button to turn the the equipment it energized a time delay relay that engaged a contactor connecting the current inrush resistor bank. Two seconds later the relay timed out disconnecting the resistor bank and energizing
a second relay that had a 3 second delay before engaging the equipment.

A lot of the larger power VSDs/VFDs do the same thing, the DC Bus supply caps are charged via a current limit resistor until the caps reach a certain voltage then and a relay cuts in and shorts the current limit resistor.
Tom... :slight_smile:

As an alternative, is it possible to limit the spark by using a potentiometer? ( attached photo)

How it works: First connect the battery using the switch, then slowly increase the output using the potentiometer.

If this approach is not good enough, I would like to know the reason.

Thanks

As an alternative, is it possible to limit the spark by using a potentiometer? ( attached photo)

How it works: First connect the battery using the switch, then slowly increase the output using the potentiometer.

If this approach is not good enough, I would like to know the reason.

So far I have not seen any current info posted for the load.
If it is sparking, the current inrush is significant which means it would fry that pot.
I think you are not seeing the big picture. When there is a current source capable of delivering substantial current
and it is connected to a load with an internal resistance low enough to draw substantial current , the electrons
arc across the gap between the contacts. The contacts do not have to be actually in contact with each other for
this arcing to occur. It is more common when DISconnecting a live load that when initially connecting it but it
occurs in both cases. A pot in series is called a rheostat (very common back in the day) but must be rated for the
maximum current, unlike the pot in the photo you posted. If you use a relay, the contacts will still arc internally
but how long the relay lasts depends on it's rating. The arcing does not occur in a semiconductor device because
electron flow is controlled by the device. There is no air gap where arcing could take place.
Typically, a timed contactor is used which connects a current inrush resistor rated for the current for about 1 second and then a second contactor engages bypassing the current inrush resistor. This can be implemented on a
smaller scale with relays. Unfortunately, since I don't know the load current or the voltage, I couldn't tell you what
resistance or power rating the resistor would need to be. If you have two relays, energized 1 second apart, the first
one connecting a current inrush resistor between the source and the load and the second one connecting the source directly to the load bypassing the current inrush resistor, the current will be minimized on turn on by the
resistor. You need to learn Ohm's Law (V=I*R => I=V/R to understand why that pot in your photo would burn up.

That pot probably will limit the inrush current sufficiently to not burn up, assuming starting from maximum resistance... but with that kind of inrush currents I expect your normal load current is way too high for a pot to handle. All that current is now passing through that pot! On top of that, you have to remember to move the pot between disconnecting and reconnecting the batteries. That's easy to forget, and will become tedious very soon.

You indeed need a double switch system. If there's an MCU in your project that's easy to implement and automate.

When you switch on the load, it's connected to the project through a low value resistor, probably something like 10Ω, depending on the capacitors you're trying to charge. That limits the inrush current, and will allow an MCU to start up. 1-2 seconds after starting up that MCU will send a signal to switch on a relay that bridges that resistor, connecting the project directly to the load.

Pot resistance ?
Load current ?
I = 36V/?

I got to thanks for your great explanations and tips, I apperciate it @raschemmel @wvmarle

Pot resistance was about to be my next question.

The Load : (the photo is attached)

Controller : 350W 36V BLDC Brushless Controller

Wheel : https://www.amazon.com/6-5-Hoverboard-Wheel-Assembly-Motor/dp/B01N7X2L90

EDIT: the photo is updated

So for starters you have 660µF worth of capacitance that wants to be charged to 36V. That's a serious current spike.

Then the load, that's up to 10A worth of DC at 36V. Gonna be a beefy relay to switch that, could be contactor territory even.

Instead of a relay a MOSFET should be able to handle this just fine. Or a pair of MOSFETs in parallel. That would be to bridge that inrush limiting resistor. Probably far cheaper and smaller a solution than a contactor.

Any MOSFET(s) you suggest?

BTW, the photo is updated.

The IRLZ44N is a common one and should do fine. There are many more.

Do check the datasheets for RDS, ON value. You may need a heat sink there.