What is it with power switches breaking?

[gerti]

What is it with power switches breaking? In the last 10 or so years I had the power switches break on:

- Hoover vacuum
- 2 desk lamps
- BT3100
- HF dust collector
- Craftsman shop vac/blower

Conspiracy of power switch manufacturers? Designers pinching too many pennies? Designers not knowing what they are doing? Cheaper materials being used than spec'd? I just don't get it.

[leehljp]

Agreed! I just replaced one on LOML's little Oreck carry-around Vac. She is after me to fix the switches on a couple of old and expensive lamps. I have to do that before Christmas and the girls and grandkids come. They certainly haven't been used much in the last 15 years or so.

[sailor55330]

I guess I've been lucky so far. I'm 0-fer.

[LCHIEN]

From an engineer's stand point it's not too bad - that's less than 1 failure per year for you (6 in ten years or 60 device-years). And that just among the devices that failed.
I'm going to assume you have numerous other appliances with large inrush currents (fractional HP motors and incandescent lamps) - power tools and other lamps. Maybe 20.

Not counting that some of the BT3100 and the HF DC have notoriously underdesigned switches then your real failure rate is probably more like 6 failures in 300 device years. which works out to about 1 in 50 years service or 2% failure rate.

Power switches have a lot of wear and tear for very cheap devices. I'll bet the average manufacturing cost is around a buck apiece (and the service parts place will sell it to you for $7 plus 8 shipping).

Switches are moving parts with a lot of electrical AND mechanical stress. A motor moves but it has no friction parts, moving surfaces are protected by metal and or ball bearings for long life. Only sacrificial carbon brushes see high wear in universal motors, induction motors have pretty much fixed and non-contacting electrical wiring and contacts. Switches are subject to large inrush currents thru the contacts and those for motors have large turn off arcs to break since the motor is inductive and inherently wants to try and keep the dynamic current constant the generated voltage will be large at turn off making a large arc at the switch contacts which degrades the contacts. Finally the switch has to work for many actuations and are almost always plastic on plastic bearing surfaces. So mostly in my experience you will have contact failures and mechanical failure of the rocker/toggle mechanism.

Sure you could make a stouter switch to last longer but consumer products being what they are, many don't get operated a lot. So that won't spend an extra buck to make a better switch so that the 10% that get heavily used will increase from 2% failure rate to less than .2%. That's what industrial quality equipment is for.

So I would say your experience is probably typical.

As an electrical engineer I'm wondering if the future holds an electronic AC switch... This switch of the future would encompass a solid state switch TRIAC plus a small circuit that senses the line crossing and only switches on or off at the zero voltage points of the AC waveforms. This would avoid arcs and stuff (even radio noise) at the time of switching and only a small, low power (read inexpensive and small component) "switch" mechanism is required to trigger the TRIAC. It could easily fit in the envelope of a mechanical switch and the costs are probably pretty close to being met today.

[gerti]

Well Loring, I should have probably added that over 30 years in Germany the only broken power switch I ever saw was damaged because something heavy banged into it. Probably because at twice the voltage they only have to switch half (more or less) the current.

Still, I think that error rate for such a simple device is too high, especially as all the devices only saw light to moderate use.

[eezlock]

power switches breaking?

Power switches are like parts to every thing made these days....cheaply made,
expendable, and usually available most places.

As to the BT3xxx saws, really a cheap switch in my opinion....way too much plastic and very little metal parts that can take the heat from repeated usage.
I like heavier duty switches....but they are like better things...you get what you pay for! These saws use a switch that actually "welds" the contacts together resulting in a constant on condition not too good in an emergency
situation. I replaced mine a long time back before it went bad with a better
unit and I'm glad I did, it was because of a bunch of other people posted about problems with theirs and their dislike of the original switch on the saw.

[LCHIEN]

Well Loring, I should have probably added that over 30 years in Germany the only broken power switch I ever saw was damaged because something heavy banged into it. Probably because at twice the voltage they only have to switch half (more or less) the current.

Still, I think that error rate for such a simple device is too high, especially as all the devices only saw light to moderate use.

I believe i pointed out that they could easily be made better but the general market finds that the price point is important and for consumer quality goods the failure level is acceptable for general market.

Higher voltage would help some as you say. Or just move back to Germany.

[lago]

Switches may be cheaply made but not cheap to replace. I have a Delta 12" lathe that is maybe 25 years old. I don't think the prior owner used it very much. I started penturning earlier this year and have hit the off/on switch quite a bit.

Last week, the switch went out on me. Contacted the switch mfg. and it is now obsolete and no replacement available. I contacted Delta and found a replacement switch but it was on back order until first of the year. Price: $56 + $10 shipping.

I found the Rockler paddle switch on sale for $25 so I bypassed the original switch and all is well.

Lago