Cheap switchs need capacitors across them?

[treez]

supposing I have a 5V battery across a 500R resistor.
Then I want to add a simple switch in series with the resistor.

If using a cheap switch (like the below one), then will I need to add a capacitor across the switch contacts so as to increase the contact arc, and allow burning away of the inevitable corrosion which will have built up on the switch contacts?...thus allowing good electrical contact?

switch: farnell 1201430
https://uk.farnell.com/c-k-components/os102011ms2qn1/switch-spdt-0-1a-12v-pcb/dp/1201430?Ntt=1201430

 

[kripacharya]

not really. The arcing happens only if you are driving an inductive load, not a plain resistor. With 5v & 500R, even the steady current is only 10ma

 

[treez]

yes I know, but I am saying that 10mA may well not be enough to give a sufficient contact arc to burn away the corrosion, and I am asking if I need to put caps across the switch contacts to increase the current at the time of contact making, so as to burn away the corrosion.
All loads are inductive to an extent (stray), and not only that but even with a non inductive load, there can still be heat at the contact at the point of switching, due to the current all flowing through a tiny area (at themolecular level) at the point of contact make/break

 

[dick_freebird]

Who told you that contact arcing is a good thing?

What you'd rather have is a contact material system
that doesn't corrode.

But you did say "cheap".

"Cheap" however does not tend to imply good arcing
tolerance either, I'd expect - the arc may in fact make
oxidation happen quicker, not slower.

 

[betwixt]

Those switches have a wiping action anyway so any build up of corrosion will be swept away as the contacts slide over each other. I will say from experience of using them in a harsh environment that spraying them with silicone grease as soon as they have been installed seems to make them more reliable but the manufacturer may dispute that and in some circumstances it could result in metal migration across the contact gap. The type of switch that suffers most from corrosion is the ones where one contact simply pushes against another. Their uneven contact surfaces inevitably mean that a small contact area is established first before the pliability of the contact material increases the contact area and the reverse happens when the pressure is released. On releasing the last point of contact is where the arc starts so a damaged spot tends to form on that point of the contacts.

I suspect the issues you are having are not related to arcing though. It's more likely you are expecting more from the switches than they are designed to give, in particular in the 'cleanliness' of making and breaking connection. Almost all switches when used in critical control circuits will use some sort of de-bouncing mechanism, either a 'lock out' monostable or a delay and recheck routine.

Brian.

 

[treez]

Who told you that contact arcing is a good thing?

What you'd rather have is a contact material system
that doesn't corrode.

yes, but everything corrodes to an extent, so the slight contact arc is needed to burn away the corrosion and make the contact...the problem comes when the switch is on a car or something with vibration, because then the vibration can "Jump" the nicely arc'd bits of switch apart, and render the connection inferior.

I have definitely read an article saying how contact arcing is needed to assure good connection by burning away corrosion......don't forget we are talking of a minute arc...very small

 

[kripacharya]

just get a better switch dude. Micro- analysing a cheapass switch for molecular damage just doesn't seem worth it.

cheers!

 

[pjmelect]

I think that a contact arc, even a small one will degrade the contacts over time and result in higher contact resistance. On some high current switches a wetting current may be used, but the discharge from a capacitor is not a good idea.