nuckolls.bob(at)cox.net
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 Posted: Thu Oct 11, 2007 11:33 am Post subject: Switch selection . . . |
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Comments/Questions: Hey Bob...
I know that in the past you have said "115 VAC rating is directly
translatable to 14 VDC applications"
I want to use these mini toggle switches on some panels I am building and I
was wondering what kind of load you think I could safely/continuously run
thorough them:
SPECIFICATIONS
Contact ratings (resistive loads): Gold plated brass; 0.4 Volt-Amps max. at
20 V max.
Silver; 3 Amps at 250 VAC, 6 Amps at 125 VAC or 4 Amps at 30 VDC
Gold plated silver; 3 Amps at 250 VAC, 6 Amps at 125 VAC or 4 Amps at 30
VDC. Gold plating withstands up to 100 mA at 30 VDC.
Initial contact resistance: 10 milliohms maximum
Insulation resistance: 1000 megohms min. at 500 VDC
Dielectric strength: 1000 V rms min. - between terminals
1500 V rms min. - between poles and terminals and frame
Electrical life: Gold: 100,000 cycles min.
Silver (at full load): SP & DP - 50,000 cycles min. 3P: 40,000 cycles min.
4P: 30,000 cycles min.
Operating temperature range: -40°C to +85°C
They are the series 5000 minis from APEM and you can see the doc on them here:
http://www.apem.com/pdf/APEM_A.pdf
Their ratings are pretty clear. They call out 4A at 30 VAC
(probably a resistive load) and 6A at 125 VAC. The DC rating
will get better as the voltage goes down . . . ergo my earlier
assertion that 125 VAC ratings sit the same pew as 14 VDC
ratings is still pretty good.
Your concerns for "safety" can be addressed only with
architecture, Plan-A/Plan-B designs and operating
philosophies. These switches are rated for 30-50K
cycles as controllers of major current . . . 100K
cycles for low currents where you don't blow the gold
off. I can tell you that none of these switches will
make it to catalog ratings . . . not because you've
poorly selected a switch but because over the decades
it takes to put that many cycles on the switch,
environmental effects will prevail.
So, once we accept the fact that EVERY switch will
fail at some point in time . . . and assuming we've
designed to be failure tolerant, then it matters
not what switches you install from a safety perspective.
The only future effect on your decisions will be on
cost of ownership.
Bob . . .
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( "Problems are the price of progress. )
( Don't bring me anything but trouble. )
( Good news weakens me.” )
( -Charles F. Kettering- )
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