Understanding Switch Rating

[Chractic]

I'm having a bit of trouble understanding how switches are rated.

If I've got a switch rated for 50mah at 48v it would be good for 2.4amps. Which at 4.2v should allow me to use 1.8ohm resistance?

Is that how it works? Why don't they just call it a 10W switch then?

I see people using switches rated for 2amps at 48v = 96watts.. wouldn't that be complete overkill?

Also, if it's an illuminated switch, that requires a nominal voltage of 2.8v to light the LED, what's the acceptable range? Could I power that straight with a 4.2v battery?

Thanks Guys!

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[Java_Az]

I'm having a bit of trouble understanding how switches are rated.

If I've got a switch rated for 50mah at 48v it would be good for 2.4amps. Which at 4.2v should allow me to use 1.8ohm resistance?

Is that how it works? Why don't they just call it a 10W switch then?

I see people using switches rated for 2amps at 48v = 96watts.. wouldn't that be complete overkill?

Also, if it's an illuminated switch, that requires a nominal voltage of 2.8v to light the LED, what's the acceptable range? Could I power that straight with a 4.2v battery?

Thanks Guys!

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If the switch is rated @ 50mA and 48 Volts That = 6 volts 400 mA. Not sure how you got 2.4 amps. Amps at lower voltages are a bit more damaging. If the switch company did the raing @ 6 volts it would be more like 6 volts 333mA Or maybe even 300mA. I guess that is the reason they dont use a wattage rating. But converting it to watts and then taking a 1/4 off is a good way to get an idea of what the switch can handle using it at a lower voltage.

Nothing wrong with overkilling a switch. Doing so you pretty much guarantee that you will get the full mechanical operations out of it and it wont die because the contacts fry out.

You should use a resistor for the LED. There should be some specs with the switch that tells you what to put into a resistor calculator. Here is a link to a calculator LED calculator for single LEDs


Edit: here is a data sheet from a switch company. You can see as the voltage rating goes down the amp rating goes up , But it doesn't correspond with the watts it is close but not quite the same. As the voltage goes down watts will go down just a fraction.

 

[Chractic]

Awesome response... thanks Java!

I see where I messed up.. need some more coffee -

48 * .050 = 2.4 took that for amps.. the switch is rated for 2.4 WATTS at the 48v dc level.

 

[Chractic]

How is the Ego able to have such a tiny switch that most can run 10watts through (ego-c 4.1v @ 1.8ohm=9.3w) But everywhere I look for switches rated for that amount of current are HUGE. I can't find a tactile switch rated for more than 3.2 watts (like here)

I need a tiny On-Mom switch that can do at least 12 watts, and not take up more room than the dang battery! Any tips or links?

Thanks!

 

[DaveP]

How is the Ego able to have such a tiny switch that most can run 10watts through (ego-c 4.1v @ 1.8ohm=9.3w) But everywhere I look for switches rated for that amount of current are HUGE. I can't find a tactile switch rated for more than 3.2 watts (like here)

I need a tiny On-Mom switch that can do at least 12 watts, and not take up more room than the dang battery! Any tips or links?

Thanks!

The eGo uses an electronic circuit called a MOSFET to drive the atomizer coil. The switch only supplies a low voltage signal through the circuit that tells the MOSFET to turn on the voltage to the coil. It can be a tiny switch as long as it is mechanically solid.

It's similar to making a phone call to have a 300 pound refrigerator delivered! The initiator doesn't do much work to have a large amount of work done.

Something like this ... The switch supplies a gate voltage to the MOSFET. The current flows through the source/drain path. The MOSFET supplies a ground to the atty circuit, one side of which is connected to the positive pole of the battery. The 47k resistor is a current limiter that prevents the switch from experiencing high current. The switch only needs to provide a logic level voltage to satisfy the gate on the MOSFET.

 

[Robert T]

The eGo uses a MOSFET for switching. There's several threads about them and they're mentioned in several more.

ETA beat me to it lol

 

[Chractic]

Ah, so shouldn't one still be able to buy a whole MOSFET switch? Petite button that comes with a little chip? Or even on board the button? I'm still impressed the ego is running 10 watts through those little tiny chips.

 

[DaveP]

Ah, so shouldn't one still be able to buy a whole MOSFET switch? Petite button that comes with a little chip? Or even on board the button? I'm still impressed the ego is running 10 watts through those little tiny chips.

I'm not sure what you are building, but Madvapes sells a box mod kit as well as a variable voltage box mod kit pretty cheap. You can buy the VV model assembled for as low $35 and the one with an LED voltage meter for $45. They also have 3.7v box mod kits for I think around $15 with instructions and all the parts, including the box.

I have one of the assembled box mods and it's solid. The box is a plastic battery box (not brittle) but it makes for a good cheap mod in a small package. The parts could probably be built into a tube 3/4" to 1" in diameter, kind of like a Lavatube.

If it's a tube mod you are working with, I can't tell you where you can get one, but someone here can, I'm sure.