fire button amps?

[bgibs1]

Hey everybody -
Im brand new to this whole modding thing. Read that as "Hey... this guy might melt something!" I have one under my belt so far, I built a altoid tin, 510 connector and push button switch into a cool little mod. I was really surprised at how well something so easy vapes. But here's my question.... A friend has suggested that a 5 amp fire button might not be safe firing my atty on a fresh charged VTC5. He thinks that I need a higher amp rated button. I've been reading for hours and cant figure if he's right or not. I put a .3 ohm build on it and it hammered, but I only did that for a couple puffs. Since then I have a 1.5 ohm kayfun on it. It worked fine with the .3 but did get a little warm. I wired the whole thing with 20 gauge wire if that matters. I'd like to get this setup to where I can drip at .5 to .8 or so. Any more electrically savvy have any input? I'd really appreciate it!

 

[Visus]

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You can add a mosfet and be done with wondering about the switch, and use any switch, even make it a touch mod. They do not take up much space.

I cannot tell ya what one works better than another it would be great to post another post if you wanna know. The one I would use is in Mamu's raptor build but its quite small.

 

[grobbins]

Jusy do the math with ohms law. And make sure a fully charged batt at 4.2v with whatever resistance you choose will keep under the 5amp limit of the switch.

 

[silentdogz]

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You can add a mosfet and be done with wondering about the switch, and use any switch, even make it a touch mod. They do not take up much space.

I cannot tell ya what one works better than another it would be great to post another post if you wanna know. The one I would use is in Mamu's raptor build but its quite small.

so what your saying, the Mosfet carries the current, and you can use a low current tactile switch...that just operates the gate?

 

[turbocad6]

many switches are rated at 5 amps, but at what voltage? a switch rated at 5 amps at 120v will have no problem carrying much higher amps at only 4.2v and you will never have a problem, hell even if it's rated at 5 amps at 12v that'll still allow you to pull well over 15 amps at 4.2v so really a "5 amp" switch should be fine as none are rated at such a low amperage anyway, so in reality it will carry much more than 5 amps in our use... and yeah a mosfet is cool, even cooler is a mosfet that controlled by a microcontroller, and has a display to show battery power and resistance of load , oh but wait, at that point you're at full vv/vw territory so only you can decide weather you want a simple mech or build a mosfet circuit or go all out and use a chip made for this purpose, like a dna30 or an sx350... yeah those are mosfets but microcontroller controlled

 

[LDS714]

so what your saying, the Mosfet carries the current, and you can use a low current tactile switch...that just operates the gate?

Exactly!

many switches are rated at 5 amps, but at what voltage? a switch rated at 5 amps at 120v will have no problem carrying much higher amps at only 4.2v and you will never have a problem, hell even if it's rated at 5 amps at 12v that'll still allow you to pull well over 15 amps at 4.2v so really a "5 amp" switch should be fine as none are rated at such a low amperage anyway, so in reality it will carry much more than 5 amps in our use... and yeah a mosfet is cool, even cooler is a mosfet that controlled by a microcontroller, and has a display to show battery power and resistance of load , oh but wait, at that point you're at full vv/vw territory so only you can decide weather you want a simple mech or build a mosfet circuit or go all out and use a chip made for this purpose, like a dna30 or an sx350... yeah those are mosfets but microcontroller controlled

I could be wrong, but don't voltage ratings for switches and fuses refer more to the arc-over voltage? For example, a fuse rated 5A @ 32V will still open at five amps irrespective of the voltage, it's just that if you have higher voltage (say 120 volts) it can continue to arc after it opens. Current is still current by Ohm's Law.

 

[stephenwhat]

So,how many amps at 4.2 volts would a switch rated for 2 amps at 48volts DC be able to handle?


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[opuscroakus]

Since there is no difference between AC amps and DC amps, other than AC flows in both directions, the answer is 2 amps. Now, that doesn't mean a switch rated for 2 amps can't handle 5, 6 or 10 amps, but pushing the higher amps through the lower rated switch will definitely reduce its lifespan.

 

[turbocad6]

2 amps at 48v is 96 watts, that switch would handle almost 23 amps at 4.2v just as easily as it would handle 2 amps at 48v

 

[rurwin]

No No No No

Watts has absolutely no meaning with switches unless you are using them as a heater.

Amps is amps. It's the same no matter what voltage they are running at. You will get away with running them above their rating if you don't mind them getting warm and failing sooner than they are supposed to. They won't explode when they fail. The worst that could happen is that they fail in the "on" state.

 

[LDS714]

2 amps at 48v is 96 watts, that switch would handle almost 23 amps at 4.2v just as easily as it would handle 2 amps at 48v

That would be incorrect.

The answer is two amps, irrespective of the voltage.

 

[DaveP]

Tubrcad6 said: 2 amps at 48v is 96 watts, that switch would handle almost 23 amps at 4.2v just as easily as it would handle 2 amps at 48v

The Switch is rated at 2 amps, regardless of the parameters it's controlling, but the amperage across the switch changes as voltage and resistance changes.

I=E/R all day long, so voltage and resistance changes the current handling capabilities proportionately. Change E or R and I moves all over the place.

Power = (E * I) or (E^2 / R) Change one and Power fluctuates.

But, the switch is rated for a maximum 2 amps working load and you have to calculate how much voltage and resistance it is controlling and stay UNDER 2 amps or it will experience premature contact failure. Stay within the design limits and it will last the predicted life.

 

[turbocad6]

yeah, I was wrong, did some googling and see, funny that I always thought the rating would be higher as the volts goes down but that's not the case afterall, sorry about that

 

[DaveP]

yeah, I was wrong, did some googling and see, funny that I always thought the rating would be higher as the volts goes down but that's not the case afterall, sorry about that

Not a problem. The best way to get a feel for the relationships is the Ohm's Law Wheel. You get multiple formulas for 4 different calculations, Watts, Volts, Amps, and Ohms.

You are partially right. The current goes down as resistance goes up or voltage goes down. Switch contacts are technically zero resistance for all practical purposes, so there's little or negligible voltage drop across it. The switch is designed with a contact made to withstand the load of a certain current level. If it were a resistor in the circuit (think atomizer coil) the current across it would rise and fall with voltage. The switch passes the sum of the current in the entire circuit and is just designed to do that.

Ohm's Law Wheel

http://www.ohmslawcalculator.com/ohms_law_calculator.php

 

[turbocad6]

wow, talk about a brain fart, and I'm no stranger to electrical circuits either, I've believed this for years too but I guess I never really thought too deep about it, made my assumption and then just always believed it. yeah an amp is an amp is an amp, the resistance required to draw one amp will change with voltage change but still an amp is an amp... it's funny how someone can make an assumption and hold it as true and then go on believing it even when it's incorrect. I feel like a ..... now

 

[stephenwhat]

What I'm wondering is how mod builders are using 3amp switches in wood box mods that are made for sub ohm. One box I saw is made specifically for super low sub ohming and uses a 3amp switch. Wouldn't it be guaranteed to fail if you push 60ps through it?


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[turbocad6]

the rated amps isn't like go past it and blow up, it's the max recommended to have an extended lifetime of the switch without it being damaged while doing it's job

higher amperage does damage, the contacts arc and they eventually practically weld to eachother but it takes serious abuse and a bit of time. if you run the switch at the rated amps it may be good for 20,000 cycles, as you go past the rated amperage the usable cycles will become much less because each cycle does a little damage.

if you tried to run 10 amps through a 3 amp switch it may only get 1,200 cycles but it will work for a while at least, I was running a 5 amp switch with a 11 amp load for a while thinking it was fine, truth is it worked fine, I was wondering if I was doing any damage to the switch, guess I was but you wouldn't know it in how well it did work

 

[DaveP]

A good way to think about electrical circuits is the water analogy. Water flowing through a hose flows with the same pressure (voltage) everywhere in the circuit. If you create a restriction (resistance) somewhere in the hose, you create a resistance to flow at that point and the pressure rises prior to that point and there's a drop in pressure past that point. In an electronic circuit, you'd measure the drop in flow across the resistor.

Pressure corresponds with voltage.
Water flow rate corresponds with amperage or current.
The size of the hose corresponds to wire gauge and resistance to flow.
Restriction at a single point corresponds to resistance and reduces flow past that point.
A cutoff valve the same size as the hose corresponds to a switch.

 

[DaveP]

the rated amps isn't like go past it and blow up, it's the max recommended to have an extended lifetime of the switch without it being damaged while doing it's job

higher amperage does damage, the contacts arc and they eventually practically weld to eachother but it takes serious abuse and a bit of time. if you run the switch at the rated amps it may be good for 20,000 cycles, as you go past the rated amperage the usable cycles will become much less because each cycle does a little damage.

if you tried to run 10 amps through a 3 amp switch it may only get 1,200 cycles but it will work for a while at least, I was running a 5 amp switch with a 11 amp load for a while thinking it was fine, truth is it worked fine, I was wondering if I was doing any damage to the switch, guess I was but you wouldn't know it in how well it did work

What happens in reality is that heavy loads create small arcs as the switch makes and breaks. It's why switches get a little finicky and resistive over time under load. If you take a switch apart after extended use you will find carbon deposits at the point of contact. When this starts you also begin to experience intermittent contact and find yourself pushing it several times to get contact and a good vape (or bright light in the case of a flashlight).

It's why electronic mod switches last longer than mechanical switches. There's much less current flow and heat going on. The MOSFET takes the load instead of the switch.

 

[mark-in-dallas]

A good way to think about electrical circuits is the water analogy. Water flowing through a hose flows with the same pressure (voltage) everywhere in the circuit. If you create a restriction (resistance) somewhere in the hose, you create a resistance to flow at that point and the pressure rises prior to that point and there's a drop in pressure past that point. In an electronic circuit, you'd measure the drop in flow across the resistor.

Great analogy and one of the first things I learned in Air Force tech school many years ago. The only thing I would add to all that's been said is that current translates to heat, which is one of the reasons why utility company power transmission lines carry extremely high voltages and use step down transformers to convert it back to usable power for end users.