Momentary switch amp rating question

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Discussion Overview

The discussion revolves around the selection of momentary switches for a battery-powered electronic cigarette, specifically focusing on the amp rating of switches at different voltages and the implications for safety and performance in high-power applications.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires whether switches rated at lower currents (e.g., 3A/250VAC) can handle higher currents at lower voltages, and how to calculate amp ratings at different voltages.
  • Another participant explains that switch ratings are complex and depend on factors like contact welding and sparking, indicating that ratings are not simply linear with voltage.
  • A different participant asserts that switches cannot handle more amps at lower voltages due to inductance in circuits, which can cause damaging voltage spikes when the switch opens.
  • Concerns are raised about the high current levels in the proposed electronic cigarette design and the lack of safety features, questioning the need for regulatory approval.
  • One participant mentions the relationship between wattage and vapor production, sharing details about their specific build and its power ratings.
  • Warnings are issued regarding the potential health risks of inhaling high-temperature vapors and the dangers associated with high heat in the device.
  • Another participant suggests that the system may be self-limiting due to the boiling of the liquid, but expresses concern about the user's understanding of the heat generated by the device.

Areas of Agreement / Disagreement

Participants express a range of views on the safety and functionality of the switches and the electronic cigarette design. There is no consensus on the amp rating implications or the safety considerations of the device.

Contextual Notes

Limitations include the lack of detailed specifications for the switches discussed, potential dependencies on specific circuit configurations, and unresolved questions about safety standards and health implications.

BaDaBooMM
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Hi all.

Hope you can help me out.

I'm making a battery powered electronic cigarette and I need a momentary switch that is rated above 20amps at 8,4v. There tons of switches out there but the ones I like are rated at 3A/250VAC or 2A/ 36V DC etc, do these switches have a higher amp rating if the voltage is lower or is this the maximum amps no matter the voltage ??
My next question would be if the switches can take more amps the lower the voltage how do I calculate the amp rating at certain voltage??


Example switch:
http://www.ebay.co.uk/itm/16mm-Star...al_Components_Supplies_ET&hash=item51b70f1510


Thanks
 
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Switch ratings are not so simple to understand. The ratings are based on several things the manufacturer must take into account. The upper current rating must not A) spot weld the contacts B) cause a pitting or sparking residue oxidizing the contact surface that would prevent future proper operation. There are probably other things as well. So no, switch ratings are not a linear voltage, current relationships. Stick to the manufacturer specs.
 
BaDaBooMM said:
My next question would be if the switches can take more amps the lower the voltage

The safe answer is "no". If there is any inductance in the circuit (and there is always some inductance in any real-world circuit!) the high voltage spike when the switch opens is caused by the current changing suddenly to zero, not by the supply voltage in the circuit. The voltage spike and the spark it generates is what causes damage to the switch.
 
BaDaBooMM said:
Hi all.

Hope you can help me out.

I'm making a battery powered electronic cigarette and I need a momentary switch that is rated above 20amps at 8,4v. There tons of switches out there but the ones I like are rated at 3A/250VAC or 2A/ 36V DC etc, do these switches have a higher amp rating if the voltage is lower or is this the maximum amps no matter the voltage ??
My next question would be if the switches can take more amps the lower the voltage how do I calculate the amp rating at certain voltage??


Example switch:
http://www.ebay.co.uk/itm/16mm-Star...al_Components_Supplies_ET&hash=item51b70f1510


Thanks

Wow, why is the current so high?

And what kind of safety considerations are there in this circuit/device? Do they need FDA approval to be on the open market? Is there an issue with completely vaporizing the liquid versus inhaling not-totally-vaporized material?
 
Thanks for all the info guys/girls.berkeman

The more wattage the more vapor.

The one I'm building has no safety at all, 2x 2665 batts rated at 50amps with a 0.42ohm coil = 168 watts, the wattage will drop down to 110watts when the batts start to drain.

Don't think they need FDA approval there are tons of this stuff on the market. Google mechanical mods they are the ecigs with no protection, no circuity. Basically a flashlight.
 
I don't know anything about what you are doing. But I would issue a word of warning about exposing your throat/lungs to high temp vapors. Just sayin!
 
mjhilger said:
I don't know anything about what you are doing. But I would issue a word of warning about exposing your throat/lungs to high temp vapors.

The system is probably self-limiting. As soon as the liquid starts to boil, the gas bubbles will reduce the heat transfer rate, so the resistance element will probably over-heat and burn out :smile:

Seriously though, the OP doesn't seem to have any idea how hot a cigarette-sized object will get, with 150 watts of heat input. I suggest an experiment with a soldering iron. Switch on a 15 watt iron for 50 seconds, then pick up the hot end in your hand. That would be a reasonable simulation of heating something with 150 watts for 5 seconds. But don't sue me if you burn your fingers doing the experiment.