Switch Amperage For a Noob.

[WharfRat1976]

4.2v/1.5 ohms = 2.8 amps
4.2v/1 ohm=4.2 amps
4,2v/.9 ohms= 4.66 amps
4.2v/.8 ohms= 5.25 amps
4.2v/.5 ohms = 8.4 amps
(and so forth)

Why do people say a 2amp or 3amp switch is good to go on an unregulated single battery diy mech mod

 

[rhelton]

If you use a actual mech mod switch yah it can handle the amps. If you use a button switch like a anti-vandal type you need to buy one rated for the amp's you plan to run thru it. Or wire in a pfet to protect it.

Is this a trick question what am I missing

 

[david4500]

Why do people say a 2amp or 3amp switch is good to go on an unregulated single battery diy mech mod

They are fools. A properly rated switch or mosfet needs to be used.

 

[WharfRat1976]

They are fools. A properly rated switch or mosfet needs to be used.

Every thread is "I use a 2amp switch and it works just fine." It is Impossible to find a 5amp or higher rated vandal switch that doesn't require a 1" plus mount hole.

 

[rhelton]

The Otto P9 is a 10amp, it is the switch used in the Duke and Hexohm

Beyond that you will need a pfet.

 

[WharfRat1976]

This switch is alleged to be rated for 12 Volt/ 60 amps and only a 19mm mount hole.

Will this work on a single battery mech box w/o a Mosfet?

2X New Momentary Push Button Off on Switch 12V 60Amp 110V 19mm | eBay

 

[WharfRat1976]

The Otto P9 is a 10amp, it is the switch used in the Duke and Hexohm

Beyond that you will need a pfet.

Great post---$18 bucks though...Looks nice.

 

[WKS01]

Why do people say a 2amp or 3amp switch is good to go on an unregulated single battery diy mech mod

Most people tend to incorrectly apply Joule's law (P=V * I) to switches in order to "rerate" them. This is not correct for two reasons, first switches are not rated by power and second they incorrectly apply the law as if the switch is seeing a voltage drop equal to the source voltage.

Switch ratings are determined for current and voltage loads the switch can handle and are independent of one another. Hence why using Joule's law is useless. It is best to think of the switch ratings as a range the switch is safe to be used. If a switch is rated at 5A / 120VAC the manufacturer is saying the switch can handle from 0-5A at 0-120VAC. It is also important to note the voltage is AC, which is quite different from DC voltage. Though it is difficult to "convert" AC ratings to DC ratings a general rule of thumb is 120VAC is equivalent to about 30VDC as far as switch ratings are concerned. So the switch with a rating of 5A / 120VAC would also be ok for 5A / 30VDC. Ideally a switch that is properly rated for DC voltage should be used.

Now if we ignore the completely incorrect application of Joule's law we can examine why it is applied incorrectly anyway. Knowing P=V*I and V=I*R we can see P also is equivalent to I²*R. Most of the time people will simply multiply the current and voltage given by the switch ratings to obtain a wattage value. Below is an example of how Joule's law is incorrectly applied for a switch rated at 5A / 120VAC.

P = V * I
P = 120VAC * 5A
P = 600W​

The issue is the voltage in Joule's law is supposed to be the voltage drop seen across the component being examined not the source voltage. This is also why it it much easier to use the alternative formula, P= I²*R, unless the voltage drop is already known. Where R is the internal resistance of the switch. For example the popular E-Switch PV6 series anti vandal switch has a maximum internal resistance of 50 milliohms according to the data sheet. Applying Joule's law gives us the following:

P = I² * R
P = (5A)² * 0.05 ohms
P = 1.25W​

This value is much lower than the other value of 600W and if anyone would stop to think about it they may see how ridiculous it sounds to say one of these small switch would be capable of dissipating 600W of heat.

Short Version: People that do not know what they are doing and incorrectly apply basic equations to obtain false answers and spread false statements.

 

[rhelton]

Here is a couple that may work

KFB2DNA1BBB CHERRY | Mouser

http://octopart.com/partsearch#!?q=otto p9&start=0&limit=10

They are cheaper than that just have to look around. You know why dont you use a pfet so you can use whatever switch you want. I paid 3 bucks for my pfet and then used a E-Switch brand button that was 4 bucks. I can only suggest you use a pfet I really dont feel comfortable helping anyone build something not safe. Most importantly to note, we are using DC power. These people use the AC ratings and think its ok.

Its not

 

[WharfRat1976]

Here is a couple that may work

KFB2DNA1BBB CHERRY | Mouser

http://octopart.com/partsearch#!?q=otto p9&start=0&limit=10

They are cheaper than that just have to look around. You know why dont you use a pfet so you can use whatever switch you want. I paid 3 bucks for my pfet and then used a E-Switch brand button that was 4 bucks. I can only suggest you use a pfet I really dont feel comfortable helping anyone build something not safe. Most importantly to note, we are using DC power. These people use the AC ratings and think its ok.

Its not

I agree and just bought a 3034 and a 15k resistor from Stearnsy on Ebay...I'm done switch hunting. I guess I am going to be the switch police everytime I see an unregulated mech without proper protection. They are everywhere. Most for sale on ebay have a Mosfet, which is good.

 

[jmeldman]

My switch on my unregulated mod rated 3A/250 and has been working fine for over 2 months


Sent from my iPad using Tapatalk

 

[rhelton]

Ok and you keep on using it ok till someone gets hurt.

Doing it the right way only costs 2.50 more in money.

But hey 2 months is a long time.

 

[david4500]

This switch is alleged to be rated for 12 Volt/ 60 amps and only a 19mm mount hole.

Will this work on a single battery mech box w/o a Mosfet?

2X New Momentary Push Button Off on Switch 12V 60Amp 110V 19mm | eBay

2-5 amps, possibly 10. Absolutely not 60 amps.

 

[JohnnyDill]

One thing I dislike regarding high amperage button switches is that they usually are very stiff, meaning you have to press pretty hard to get them to trip. This is not something I would want for the button I want to press often.............

 

[Quigsworth]

Another option is most peeps that have the skills to build a mod can build they're own mech switch...I use the beryllium/silver contacts I cut out of heavy duty DC relays, they can be picked up for pretty cheap and depending on how you configure it you can get a nice tight form factor... I've built a few and so has Johnny dill

Good post wharf... but I've long given up trying to convince those saying "I've been sub ohming on a 2A switch and it works perfect" that they are at best going to be replacing it in a week or at worst, vaping on a potential bomb.

Btw... not really buying the 60A rating on that linked switch

 

[WharfRat1976]

2-5 amps, possibly 10. Absolutely not 60 amps.

Thanks for the confirm. Too good to be true.

I ordered Mosfets from Stearnsy...

 

[rhelton]

Not trying to steal your thread but what are these switches you guys are making can you show me.

 

[WharfRat1976]

Not trying to steal your thread but what are these switches you guys are making can you show me.

We are not making switches. The OP was about how insane it is to put in a 2amp-5amp+ switch into an unregulated device. The conclusion was that a FET transistor to take the majority of the work load off the flimsy switch is the right thing to do.

 

[david4500]

Not trying to steal your thread but what are these switches you guys are making can you show me.

http://www.e-cigarette-forum.com/fo...tch-if-anyone-cares-world-regulated-mods.html

 

[SupplyDaddy]

It also depends on what your diy box/mod is for. None of mine are designed for sub-ohming and any one that gets one has that information rammed into their head by me, Before they get one.
5 amp switches are what I use, which I can find all day long, for my mods. Of course, I also use 18 gauge wire, another limiter, and fuses as needed to keep the voltage down.
I guess it so helps that Most of my mods are 14500's.. the best battery usually is maxed at around 4.7 amps with those.

~sent from my galaxy mega using taptalk~