So i bought CK1050 rotary switch i now i realized that it's rated only for 150mA 250V AC/DC on the data sheet. I need to use it with 12V DC at 450mA so will it be safe? If you think the watts it should be safe 250V*0.15A=37.5W and 12V*0.45A=5.4W

  • \$\begingroup\$ Probably, if the load is resistive- its current carrying capacity is listed at 5A "non switching", but if you want to be sure you should contact the manufacturer for advice. If your load is inductive without snubbing or capacitive without much current limiting it may truncate the life of the switch. \$\endgroup\$ – Spehro Pefhany Apr 10 '16 at 19:30
  • \$\begingroup\$ No, it will not be safe. You want to run 30x more current than it's rated for. (Next time, check parameters before ordering a part.) \$\endgroup\$ – Nick Alexeev Apr 10 '16 at 19:32
  • \$\begingroup\$ @NickAlexeev - Check the data sheet 15 mA is a typo. \$\endgroup\$ – WhatRoughBeast Apr 10 '16 at 20:17

You completely misunderstand the ratings. Power, as you calculate it, is irrelevant. All that matters is the current. You seem to want to switch 450 mA with a switch rated for 150 mA. So, no, you can't do it - or at least you can't do it too many times before it fails.

The only possible workaround is to turn off your power supply when switching. In this case, the load current will be zero when switching, and when the power supply comes back on, the non-switching limit (5 amps) will permit operation.

  • \$\begingroup\$ Thanks for the great answer! What you think is best way to get around it? maybe relay or transistor? \$\endgroup\$ – Jussi Roos Apr 10 '16 at 19:56
  • \$\begingroup\$ Easiest is a relay. Just make sure the coil is 12 volts and less than 150 mA, while the contacts are rated for more than 450 mA. \$\endgroup\$ – WhatRoughBeast Apr 10 '16 at 20:18

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