phantom power toggle switches

[pucho812]

I am certain this is simple, I am certain I am overthinking things.
But I need some toggles for a project.  I can't find any that are rated  for above 48VDC. I see plenty rated for 250VAC at various amps. Those same switches also have VDC ratings and it is far below 48VDC.  since the current is so low does it matter that I am exceeding the switch rating.  I say it does, yet I keep reading I am o.k. because of such a low current.
what is fact vs fiction?

 

[JohnRoberts]

I am certain this is simple, I am certain I am overthinking things.
But I need some toggles for a project.  I can't find any that are rated  for above 48VDC. I see plenty rated for 250VAC at various amps. Those same switches also have VDC ratings and it is far below 48VDC.  since the current is so low does it matter that I am exceeding the switch rating.  I say it does, yet I keep reading I am o.k. because of such a low current.
what is fact vs fiction?

are you sure about those specs?

The higher AC voltage may be dielectric breakdown not the switch contact rating (two different things).

There were a pile of 48V DC rated switches on digikey when I just checked.

JR

 

[Bo Deadly]

The standard mini-toggle is fine. Datasheets usually say they're good at some voltage up to some current (like 30V / 4A) over which the gold plating can be burned off from arcing. But at lower current you can use higher voltage accordingly. I'm not sure if the VA rating scales like other parts or if the higher voltage increases the risk of arcing but for phantom power you're talking about 20mA depending on how much current you want going though the LED. That's nothing. That switch will lead a long and happy life.

 

[pucho812]

are you sure about those specs?

The higher AC voltage may be dielectric breakdown not the switch contact rating (two different things).

There were a pile of 48V DC rated switches on digikey when I just checked.

JR

Yes John. I pulled them directly from newark. 

 

[pucho812]

The standard mini-toggle is fine. Datasheets usually say they're good at some voltage up to some current (like 30V / 4A) over which the gold plating can be burned off from arcing. But at lower current you can use higher voltage accordingly. I'm not sure if the VA rating scales like other parts or if the higher voltage increases the risk of arcing but for phantom power you're talking about 20mA depending on how much current you want going though the LED. That's nothing. That switch will lead a long and happy life.

excellent.  just needed that assurance. 

 

[JohnRoberts]

Yes John. I pulled them directly from newark.

I am not sure that I really want to know but how about a link...

I just went to newark, ran a filter for 48V dc and looked at the spec sheet for the only switch cheaper than $5

It basically said 48V ac or dc.

JR

 

[pucho812]

http://www.newark.com/multicomp/1md1t1b5m1qe/switch-toggle-dpdt-5a-250v/dp/98K4949?ost=1MD1T1B5M1QE&scope=partnumberlookahead&exaMfpn=true&searchref=searchlookahead&ddkey=http%3Aen-US%2FElement14_US%2Fw%2Fsearch

 

[PRR]

> rated  for above 48VDC.

So, what.... 49V? 49,000V?

What is the load? A big motor? Coil? Capacitor? Or mostly resistance?

The real issue is that when you break AC, the arc will go out in 1/120th of a second; big DC can arc forever. Big DC switching needs quite special construction.

Also testing. Clearly the $0.99 Radio Shack knife-switch (Frankenstein movie) will break 300V DC, if you flip it wide open quickly, but why should they bother to test it? Would you dare to break 300V on bare knives?

A specific model of Carling vacuum-cleaner switch has been used in millions of guitar amps to break B+ (standby) and gives no trouble.

 

[Monte McGuire]

The only gotcha I can see is that you need to make sure that the P48 switch is not loaded directly into a filter cap - charging that cap for 0 to 48V will require a large current spike. Make sure that there's some resistance after the switch, before any local filter caps, or put the switch after the caps but before the P48 series resistors. Just make sure to limit the peak current, which is only severe if you're charging a filter cap.

 

[JohnRoberts]

http://www.newark.com/multicomp/1md1t1b5m1qe/switch-toggle-dpdt-5a-250v/dp/98K4949?ost=1MD1T1B5M1QE&scope=partnumberlookahead&exaMfpn=true&searchref=searchlookahead&ddkey=http%3Aen-US%2FElement14_US%2Fw%2Fsearch

The data sheet for that part says 1000V rms at sea level.. so adjust for your altitude.  ;D

I think 48V will easily be < 1000V, even in CA that is higher than the rest of the country.  8)

JR

 

[pucho812]

The data sheet for that part says 1000V rms at sea level.. so adjust for your altitude.  ;D

I think 48V will easily be < 1000V, even in CA that is higher than the rest of the country.  8)

JR

I must have been looking in the wrong part of the sheet or whatever, it would not be the first or the last time that happens.

Thanks john..

 

[ruffrecords]

The data sheet for that part says 1000V rms at sea level.. so adjust for your altitude.  ;D

I think 48V will easily be < 1000V, even in CA that is higher than the rest of the country.  8)

JR

That's the dielectric strength. I think what concerns him is this bit at the bottom of the data sheet.

Cheers

Ian

 

[Bo Deadly]

Actually 0.4 VA does seem really low even if the voltage is referring to RMS. I guess maybe it makes a difference that the 48V is only applied for a short time as the filter cap charges up? But I wonder if it is justified to use a larger resistor / smaller capacitor in the RC filter. With a 100R there will be an instant where you have 48V across 100R which is quite a lot of power for a 0.4 VA part. Then again, those mini-toggles have been used for phantom forever without problems AFAIK.

 

[abbey road d enfer]

The 0.4VA contacts are dedicated to switching low-level signals, typically audio signals in low (200) to high (100k) loads. They are gold-flashed so they don't contaminate.
The other type is generally siver-flashed and relies on the switching arc to de-contaminate the contact. I would use this type for phantom power switching.

 

[Bo Deadly]

The 0.4VA contacts are dedicated to switching low-level signals, typically audio signals in low (200) to high (100k) loads. They are gold-flashed so they don't contaminate.
The other type is generally siver-flashed and relies on the switching arc to de-contaminate the contact. I would use this type for phantom power switching.

Interesting! Well that's a useful tidbit.