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Author Topic: Snap disc switches - thermal management  (Read 3783 times)

joecool85

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Snap disc switches - thermal management
« on: December 19, 2012, 12:02:17 PM »
I just installed a snap disc to trigger a shutdown of our servers at work.  These things work all the way below freezing and up to 300+F.  Tons of different mounting configs and temp ranges.  They go for about $10 each and are made in the USA.  I'm thinking it'd be real easy to install one on a heatsink and have it shut the amp down or turn on a fan.  No added noise in the circuitry and keeps it simple.

Check 'em out: senasys.com
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Enzo

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Re: Snap disc switches - thermal management
« Reply #1 on: December 19, 2012, 02:33:51 PM »
Too late.  Yep, shut off the mains, turn on a fan, turn up the fan speed, and you left out turn off the speaker.  They come in both make and break versions.  Mouser sells them for under $5.

Peavey for one has been using them in their products at least since the mid 1970s for exactly those purposes.   A quick look at Fender and I see them as long ago as the M80 series.

Other names for them are thermostat and thermal switch.

We tend to use the self-resetting type, but they also have them that trip and include a reset button.  My home furnace uses the reset button type in the flame sensor protection.

joecool85

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Re: Snap disc switches - thermal management
« Reply #2 on: December 19, 2012, 03:54:59 PM »
Mouser may sell them for under $5, but I doubt they are made in the USA (a big deal to me).

Also, I knew they have been used in other industries (particularly HVAC) for 50+ years but didn't know they were in guitar amps.  I guess smart minds thing alike?
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Enzo

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Re: Snap disc switches - thermal management
« Reply #3 on: December 19, 2012, 07:26:52 PM »
Yep, open up most any PV amp, well SS anyway, and look for a pair of blue wires twisted, likely goes to one of them..

The Mouser ones are from White-Rodgers.  The data sheets don't include country of origin, so I don;t know.  I am more familiar with the Selco line of similar sensors.  They have factories in Reno and San Diego, but they also have plants in SOuth America, Europe, and Asia.  SO again I am not sure which plants make the sensors.

joecool85

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Re: Snap disc switches - thermal management
« Reply #4 on: December 19, 2012, 07:40:06 PM »
Well regardless of where you get them, it seems that snap discs are a good way to go - cheap, simple and effective.
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Enzo

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Re: Snap disc switches - thermal management
« Reply #5 on: December 19, 2012, 10:52:56 PM »
Oh, no argument there.

Roly

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Re: Snap disc switches - thermal management
« Reply #6 on: December 19, 2012, 11:47:45 PM »
These are widely used, not only for ordinary thermostat control, but doubled up in staggered temperatures for normal and "last-ditch" protection; e.g. the low temp one turns on the fan while the high temp one cuts the power.

Internally they are a bi-metal disk that snaps from concave to convex at the rated temperature.  I used to have a couple of disks out of a dead water heater thermostat on my workshop windowsill and when the sun came around on them they would "ping" up in the air like jumping beans.   :cheesy:
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

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Re: Snap disc switches - thermal management
« Reply #7 on: December 20, 2012, 06:54:40 PM »
They used to make, and maybe still do, little toy disks.  I see them mostly as imprinted items to give away at trade shows.  You hold the disc in your hand and rub with your thumb and pop it to concave, then sit it on the table, and after a moment or so it goes PING and makes a snap noise and jumps.

Yes, for example the Peavey CS800 that is everywhere.  Uses one for fan speed and another to open the mains lead.

gbono

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Re: Snap disc switches - thermal management
« Reply #8 on: December 21, 2012, 02:35:29 PM »
Sunn used these on the Concert and possibly Coliseum series. Nothing is new under the sun (hehehe)

J M Fahey

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Re: Snap disc switches - thermal management
« Reply #9 on: December 22, 2012, 11:48:37 AM »
Yes, now China mekes them for less than 1 U$.
Down to 14 centsif you buy 5000 , which probably Peavey and others do.
Impossible to beat those prices.
I remember a Chinese commercial delegation visiting Argentina in the 70's , they were eoffereing some very crude oscilloscopes, and told me they *had* to make their own transistors, because they were not available and nothing could be imported, how's that?
Worst thing is that the Chinese monster who is going to swallow us all, is fully a US creation, starting with Nixon's travel in '75.
Such growth would have been *impossible*without US capital, technology, help and free access to market.
Oh well.

Roly

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Re: Snap disc switches - thermal management
« Reply #10 on: December 23, 2012, 03:19:26 AM »
Solidaridad bro.  :dbtu:

A pig in a minefield, that's Australia's role;

"Gough Whitlam and his Labor entourage on their historic 1971 visit to China. And it came against a background of widespread community fear of China"


Gough Whitlam    31 Oct 1973    Whitlam in China
The first visit of an Australian Prime Minister to China marked Australia’s trade agreement with the People's Republic of China. Gough Whitlam had visited China in 1971, as part of a Labor Party delegation, a month before United States President Nixon made his historic visit.
http://primeministers.naa.gov.au/timeline/results.aspx?type=pm&pm=Gough%20Whitlam

This period, first hand (long, detailed)
http://www.afr.com/p/lifestyle/review/whitlam_china_masterstroke_7rfoUh2Upmy0kZb9oyzJxN
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

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Re: Snap disc switches - thermal management
« Reply #11 on: December 23, 2012, 04:12:17 PM »
Impressive post, thanks a lot.
It's incrediblw how businessmen always want to increase their personal profit (so far, fine with me), even destroying jobs at home.  :trouble :grr
Not fine with me at all.
And this guy was a *LABOR* politician !!!
He also mentions that even in the middle of a war with China (Vietnam), and no diplomatic relations at all, there was already $80Million trade.
Multiply that by 10 , we are talking 60's Dollars !!!!
He also mentions that Dunlop (rubber products) was already buying tennis shoes from China.:
Quote
John Gough was the footwear manager at the consumer goods company Dunlop when Whitlam travelled to China in 1971 and was already importing Chinese-made shoes following a Melbourne competitor later turned business associate, Paul Winestock.

Gough, who went on to become chairman of Pacific Dunlop, says the small and ill-equipped Chinese factories seemed more comfortable with the modest orders they were getting from Dunlop than periodic attempts by American or European importers to place large orders.

“And your shoes couldn’t be high fashion because by the time they were delivered they wouldn’t be,” he says. After initially buying from the agents in Canton, Dunlop quickly gained their confidence and was invited to the trading company head offices in Beijing. It was then allowed to have the coveted direct contact with factories.

As buyer and sellers gained more familiarity with each other, Dunlop became involved in helping improve the production equipment which Gough says put the company several years ahead of other foreign shoe retailers sourcing from China.

The expected move to cut Australian tariffs was already on the minds of manufacturing company executives like Gough and Grimwade as diplomatic recognition occurred, while others were just focused on selling wool, wheat, animal hides and minerals.

So, nothing comes out of the blue, catastrophes take long years to develop, nobody could ignore what would eventually happen, China becoming "the Factory of the World"
Oh well, thanks again.

PS: and of course you already documented what happened to those great Australian amp makers.

Roly

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Re: Snap disc switches - thermal management
« Reply #12 on: December 24, 2012, 06:32:02 AM »
Not only was Gough a Labor politician, from the American perspective he was a "communist" (ref the book "The Snowman and the Falcon" which touches on the CIA role in the sacking of the Whitlam government).

Apart from living through this period I also witnessed the impact on Aussie manufacturing.  Some time later there were tariff changes that demolished Textiles, Clothing & Footwear, "TCF", throwing roughly 45,000 people out of work, mainly women from non-English speaking backgrounds - and of course those companies that serviced TCF (such as the one I worked for) suddenly had a big hole in their client list.

"Structural change" they call it - like having the roof cave in. 
If you say theory and practice don't agree you haven't applied enough theory.