Switches.

[Baske7Cas3]

What does it mean if it says that a switch's contacts are rated 25A at 12VDC? I know that the contacts are the metal prong things sticking out of the switch, and I know what 25A and 12VDC, but I was wondering what it actually meant.... Like can it only let 25A and 12VDC through the switch? I am just wondering.

 

[3v0]

What does it mean if it says that a switch's contacts are rated 25A at 12VDC? I know that the contacts are the metal prong things sticking out of the switch,

Not exactly. The contacts are usually within the switch hidden from view. The metal prongs are connected to them. Perhaps in some switches they are the same piece of metal.

and I know what 25A and 12VDC, but I was wondering what it actually meant.... Like can it only let 25A and 12VDC through the switch? I am just wondering.

In this case it means that the contacts are able to carry 25A at 12VDC without overloading them. It is an upper limit.

 

[Baske7Cas3]

Well, how many volts do you think it would be able to carry if it was under 1 amp? or is it still the same amount of volts?

 

[Sceadwian]

You'd have to contact the maker of the switches, because construction can vary so widely there's no simple way to derate a switch for higher voltage. Also keep in mind that the current rateing for a switch usually isn't what it can safely switch off. For example an inductive motor might draw the full 25 amps at start and at running speed only draw 2-3 amps. But it's usually not safe to turn a switch off under it's full rated current otherwise arcing and possibly contact welding may occur. If you're not sure set up a test sitatuation that mimicks your load with a fuse on the line and a fire extiguisher handy.

 

[Nigel Goodwin]

Well, how many volts do you think it would be able to carry if it was under 1 amp? or is it still the same amount of volts?

Generally the same - the voltage rating is mostly dependent on the seperation gap of the switch. Also be aware that the current rating is usually considerably lower for DC than AC.

 

[things]

if this is for the camera shock setup?, the switch should be able to handle 300 volts, but if you flick the switch, then start charging, it will work

 

[Baske7Cas3]

Hmmm... what do you mean things? What I want is just a switch for it to start charging, so I flip the switch and it charges the flash capacitor, but isn't that well over 12v? I am curious as to how it would be able to handle 300 volts when it is rated for 12v...

So here is how it is going to work... I make a break in the connection with the switch, then I flip the switch and it makes the connection, hen it starts charging the capacitor... I am just not sure how it is supposed to stand however many volts it is receiving. I also doubt it is receiving 330v cuz that is just how much the capacitor holds once its charged, and it takes a couple of seconds for it to charge.

 

[things]

is the switch to start charging the capacitors? or is to connect the second capacitor?(if you have one)? the switch is rated for 12 volts @25 amps, but with the caps, they are charged to something like 300 volts, but at a low milliamperage (1-3)ma. if the switch is to replace that little metal thing on the bottom, it doesn't have 300 volts through it, only something like 1.5 volts, which then goes to the transformer, and then the transformer steps up the voltage to 300 volts

 

[Baske7Cas3]

Ohhhh.... ok... ya, it is to replace the little metal thing on the bottom.

Now then, what kind of switch would I need to connect the second capacitor then?

 

[things]

basically any plastic cased switch, but at a reasonable size

 

[Baske7Cas3]

I have plastic cased switches, but they all have metal tops and metal handles... And how is 250v?

 

[things]

250 volts are good, but discharge the capacitors first, then flick the switch, then charge them both if it has a metal handle. if you don't, you have a good chance you will get shocked through the the handle.

 

[Baske7Cas3]

Ya, I need to have the switch on or off anyways in case I want both or one... so im never gonna touch it while it is charging.

But how can it shock me through the handle? It couldn't if I only touch it with one finger to switch it could it?

 

[things]

never gonna touch it while it is charging.

or charged well actually if it's rated for 250 volts, it shouldn't shock you, but anything under 50 volts rated probably would

 

[Baske7Cas3]

Ya ok... cool lol, thx a lot for your help, now that I have a project case and everything I am gonna set it up tonight/tomorrow. I will probably just get it laid out tonight and then to the rest tomorrow. The only problem I have as of now is connecting the two wires to the metal plates on the bottom I don't have a pencil solder I have an old solder gun which is to big to be accurate.

 

[RODALCO]

Might be an idea to save up for a good temperature controlled soldering station,
they are worth the extra money, especially when you solder a lot.

Soldering guns can also damage CMOS components.
Quite often the tip of the gun is floating with respect to earth and may damage static sensitive devices.

 

[Obmar]

Baske7Cas3,
There is also a difference between voltage rating of contacts on AC and DC supply. On DC, the current is constantly flowing through the contact while in AC it is almost zero at change over point and fluctuates. The contact rating, therefore, is lower for DC than equivalent AC. The difference is more important during opening of the contact. On DC the sparking would be more than on AC (as spark will be cut-off automatically on AC) and hence contact rating lower.

Does this help in point under discussion?

 

[things]

good point ROLDALCO.
yea, thats if you don't want the contacts to weld together