Current handling spec for rotary switch

[JuiceKing]

Hi,

I'm looking at 2P4T switches. The maximum load it needs to switch is 25V at 0.25A VRMS.

Holy smokes, these switches are expensive. And, they don't even meet this spec. For example:

   SWITCH, ROTARY, DP4T, 200mA, 220V
   No. of Poles: 2
   No. of Switch Positions: 4
   Angle of Throw: 45°
   Contact Current AC Max: 150mA
   Contact Current DC Max: 200mA
   Contact Voltage AC Max: 220V
   Contact Voltage DC Max: 28V
   Circuitry: DP4T

This one is rated at 150mA, but I don't need 220V. Can I expect it to handle 250mA at 25V without a problem?

- Ken

[mariush]

Is that DC or AC?  There's 2 different limits for them...

 Contact Voltage DC Max: 28V
 Contact Current DC Max: 200mA

250mA is a bit higher than 200mA, the max current listed.  If in average you're going to have less than 200mA on it, I would say maybe they'll work, I'm not sure.

[JuiceKing]

Is that DC or AC?  There's 2 different limits for them...

 Contact Voltage DC Max: 28V
 Contact Current DC Max: 200mA

250mA is a bit higher than 200mA, the max current listed.  If in average you're going to have less than 200mA on it, I would say maybe they'll work, I'm not sure.

AC. My current requirements are 250mA and the switch is rated at 150mA. However, I will only put 25VAC across it, and the switch is rated much higher. So, if power is the real concern, it's fine. But if current rating must be respected even at a lower voltage, I need a higher spec part--more money and none in stock (at least none at Newark).

- Ken

[SeanB]

No, it can handle 150Ma AC only, and any voltage from zero to 220VAC. So 25 VAC is in the range for voltage, but the current is rather over the limit. That being said, if you are going to have few operations of the switch, or are prepared to have a life considerably less than rated, you can use it at this overload. If the current is only to be carried but the switched current is low then it will work.

[T4P]

I think you'll need to settle to use a lower rated switch to switch on a transistor ...
I THINK of course.

[HardBoot]

I wouldn't worry about it's spec too much, just gotta check it's contact resistance when running your worst-case current through it.

[JuiceKing]

Many thanks for the help here.

I looked around some more and found to my surprise that I could save money by getting a switch with exactly the capacity I need at lower cost by filtering for one with MORE poles than I need. I guess I happened to filter by a odd-ball configuration that they don't stock or don't buy in quantity.

It is harder than it should be to shop for parts on line.