PTC as a Spark Suppressor

1

Hi,

I found a youtube video showing a Spark Suppressor used to protect the connector of large ESC and LiPo batteried. But the blogger did not specify the PTC he used. Are you able to research the specification of the PTC. Here’s the youtube vifdeo and a schematic.

I am using a switch instead of the touch and plug concept in my diagram.

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Regards,
Carlou

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2

Hi Carlou, Welcome to the forum :smiley:

The youtube description lists a 47 Ohm 2 Watt resistor. There is also a link to a blog with some photos of the resistor used and it looks to be a fairly generic resistor.
Is there a particular reason you wanted to use a PTC resettable fuse, instead of a run of the mill resistor?

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Yes one version of the Spark Suppressor is using a resistor and the other version is using a PTC. I thought the PTC would be better than a resistor. Here’s the PTC Version. Kindly advise if the PTC you have can be used in this application?

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Hi Carlou,

At room temperature, this PTC will have a resistance of as low as 1.25 Ohms, I don’t know what sort of current needs to flow before you will experience arcing but your single battery shouldn’t exceed its current rating and damage the PTC.
There will be a small delay as the resistance ramps up in the PTC so it will still have an initial current surge, but we’d need to look into it further to know if 1.25 Ohms is sufficient resistance to prevent an arc.

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5

Hi all
Don’t particularly agree with using what used to be known as a “poly fuse” for this application.
It is what the name implies, a fuse (resettable) which means it is current activated. This means that if a malfunction happens on the load side causing excessive current the device will operate. It heats up and the resistance rises sharply thus reducing the current. The resistance rises to a point where just enough current is passed to maintain temperature and an equilibrium is reached where the device remains hot while only allowing a small enough current to pass which will not normally damage the supply. Normally you would remove the offending equipment (thus resetting the fuse), repair or replace and everyone is back in business.

I have not had occasion to try this but maybe if the poly fuse is activated by inrush current there is a possibility it will stay activated and prevent the load equipment operating correctly.

The trip current etc of different devices is available in data sheets. Jaycar stock a few and make the data for stocked units available in the catalog, P156.

I have used these devices where a number of load equipments are powered from one source and it is very undesirable to have one faulty unit bringing down the whole lot due to power supply shut down. This was part of a very high reliability system where the implications of losing a number of units due to one faulty one were very nasty indeed. Such as Air Traffic Control.
Cheers Bob

Edit: It may be worth while to investigate how battery chargers handle this. Most modern chargers will not spark when connected but I have had no reason to date to find out how this is done.

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