Hi all, I’m looking for a DPDT on/on 15A/125VAC toggle switch with contact resistance that is both quite low (ideally under 20 milliohms) and quite consistent (ideally no more than +/- 2 milliohms variation from unit to unit.) This doesn’t have to be a super cheap switch, but it also isn’t a price-no-object application. Does anyone have a recommendation?
Welcome to the forum
Don’t know of any toggle switch manufacturer that makes a part with a guaranteed maximum unit to unit variation.
Generally they only specify a maximum contact resistance so the tolerance includes zero ohms. e.g. 10 milliohm maximum switch is 5 milliohm +/-5 milliohm.
You may need to do a custom order from one of the manufacturers to get a +/-2 milliohm spec.
Another thing you will need to specify is over how many cycles you need the unit to unit tolerance to apply. A switch’s contact resistance will vary throughout it’s lifetime based on usage and environmental exposure.
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Fair enough, thanks Paul! I don’t have anything close to the resources for a custom order at this point, so is there a manufacturer or part you’d recommend for a 10 milliohm max (or lower, if that exists under say $30 each) switch?
Also, it seems like practically speaking the range can’t actually include 0 ohms, do toggle switch contacts get extremely close? If there’s a minimum practical resistance of even a couple milliohms that would narrow the tolerance significantly (i e 6 +/- 4 instead of 5 +/- 5.)
As for lifecycle, I’d be surprised if one of these got flipped more than a thousand times in its life so from the specs I’m seeing I don’t think wear should be a problem (should it?), how often do you think one of these switches should see contact cleaner in a dry indoor environment to stay in spec?
Hello,
Welcome to the DigiKey TechForum. Take a look at this S series switch from NKK, DigiKey part number 360-2911-ND. The datasheet shows the Contact Resistance: 10 milliohms maximum for this series.
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Thanks so much Steve, that looks perfect!
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From a manufacturing standpoint guaranteeing a minimum resistance is a large economic burden that almost nobody is willing to pay for.
You can add a minimum resistance in series with the switch contacts to achieve the same effect at a much lower cost than the manufacturer can.
Again it’s a manufacturer trying to offer a practical guarantee of performance. The maximum contact resistance spec (unless otherwise noted) is guaranteed over the minimum number of switch cycles specified as the part life.
Adding contact cleaner voids the manufacturers warranty.