mechanical box mod fire button

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WKS01

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Here is a link to a thread I started in another forum. might help you out a bit.

Switches?

Please do not listen to the information about switches in that thread. If a switch is rated at 2A @ 48VDC that means it is ok for use from 0-2A at 0-48VDC. If you lower the voltage of the switch it does not increase the amperage rating.
 

disturbed1

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Please do not listen to the information about switches in that thread. If a switch is rated at 2A @ 48VDC that means it is ok for use from 0-2A at 0-48VDC. If you lower the voltage of the switch it does not increase the amperage rating.


Pleas explain a little more. As I don't want bad things to happen. I thout the info would be good coming from Breaktru.
 

WKS01

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Many people have the incorrect notion in their head that if you lower the voltage of the switch the amperage increases. This is furthered by incorrectly applying the power calculation to the switch, as shown below for determining the current of the switch at 48VDC instead of the rated 120VDC.

Example Switch Rating 2A @ 120VDC (This is the incorrect way of rating a switch at various voltage levels!)

P= V*I

P=120*2

P=240 Watts

240=48*A

A=5 Amps


This is not the correct way to calculate the amp limit of a switch EVER! The ratings of a switch imply the maximum current the switch can take, which is based on the contact geometry, material, etc., and not run the risk of failure such as fusing the contacts closed or corroding them open. The maximum voltage is relates to the air gap in the switch and is the highest value of voltage that can be run through the switch before you risk the air gap not being large enough to stop the spark that occurs when using the switch.

**To recap: A switch rating implies that the switch is suitable for use from 0-X amps while being used at 0-Y voltage.

Another area people tend to get in trouble is attempting to convert ratings for AC voltage to DC voltage. AC and DC voltages are quite different, with DC voltage being much more degrading on a switch as it does not have the 100/120 zero current points per second as AC voltage does. This is way you see the switch ratings have lower amp limits at lower voltage for DC compared with AC. Without the zero current moments the switch takes the full brute power of the DC current and is damaged more than the same current and voltage level in an AC system.

Now it is possible to derate a switch from AC to DC to obtain a rough idea of what the switch may handle, but those are not 100% accurate methods. The best way to know a switch is suited for your application is to use a switch rated for your application.
 
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