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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Bimetalic domes
As used in thermal switches. Instead of in form of a bimetal strip and
continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? |
#2
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Bimetalic domes
Sure you can do this, but get a few of these, as the odds of getting it right the 1st time is slim.
Steve "N_Cook" wrote in message ... As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? |
#3
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Bimetalic domes
How important is the overall size of the sensor?
You might find one of the sort that used to be used in kitchen appliances, that could be inserted in a grill, waffle maker, cookpot, etc. These have adjustable settings, which (I assume) are varied by changing the pressure on the sensor. |
#4
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Bimetalic domes
Steve Lusardi wrote in message
... Sure you can do this, but get a few of these, as the odds of getting it right the 1st time is slim. Steve "N_Cook" wrote in message ... As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? According to patent "Laser adjusted set-point of bimetallic thermal disc" it is done at production , for precise adjustment, but no specific details of patterns/which surface/degree of variation. I'm more interested in adjusting otherwise useless batch made for set point of 16 degree C up to 50 or 60 degree C, with no great precision, +/- 10 deg C would be fine |
#5
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Bimetalic domes
According to patent
"Laser adjusted set-point of bimetallic thermal disc" it is done at production , for precise adjustment, but no specific details of patterns/which surface/degree of variation. I'm more interested in adjusting otherwise useless batch made for set point of 16 degree C up to 50 or 60 degree C, with no great precision, +/- 10 deg C would be fine If you could find the patent for the controller I described (it's a famous patent, from a man who patented many devices in the 50s and 60s), it might show how this is done. |
#6
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Bimetalic domes
William Sommerwerck wrote in message
... According to patent "Laser adjusted set-point of bimetallic thermal disc" it is done at production , for precise adjustment, but no specific details of patterns/which surface/degree of variation. I'm more interested in adjusting otherwise useless batch made for set point of 16 degree C up to 50 or 60 degree C, with no great precision, +/- 10 deg C would be fine If you could find the patent for the controller I described (it's a famous patent, from a man who patented many devices in the 50s and 60s), it might show how this is done. probably a John Taylor http://content.yudu.com/A15ex7/Apro9/resources/8.htm but no further forward, I'll suck some and see |
#7
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Bimetalic domes
probably a John Taylor
http://content.yudu.com/A15ex7/Apro9/resources/8.htm I'm not sure. The guy I'm thinking of is American. |
#8
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Bimetalic domes
Interesting , but no further forward. Looks as though these froststats will
remain froststats. Surprising ping and bounce as much as six inches on change of state, the loud ping is somewhat damped when inside the casing. Need freezer spray to change the state of these discs (hysteresis and all that). When back to body temp I tried grinding a spot in the centre of the concave side, no change in set temp. Tried 4 diametrical marks on the concave side , no change in response. Tried deeper but small 8 cuts just on the perphery, now no ping but slowly migrates from one state to the other , still requiring freezer spray. I wonder how they "weld" these 2 materials together. |
#9
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Bimetalic domes
On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote:
As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Like this? http://www.google.com/patents/about?id=VQ4XAAAAEBAJ&dq=5903210 or this? http://www.google.com/patents/about?id=BygyAAAAEBAJ&dq=3852697 Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I don't think so (but I'm guessing). Grinding might change the deflection or force but probably not the transition temperature. Below some force level, it simply will not transition. My guess(tm) is that the transition temperature is controlled by the curvature which is rather difficult to modify. Note that some discs are "manual reset" or "single operation" and act as thermal fuses. Search Google for "bimetallic snap disk". http://www.cpi-nj.com/snap.htm http://www.thermodisc.com (etc...) I tried to find the vendor of the actual discs, which might include design information, but couldn't find anything useful. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#10
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Bimetalic domes
On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote:
As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? Have you considered fire alarm heat sensors? They use a bimetal switch internally. Gunner "IMHO, some people here give Jeff far more attention than he deserves, but obviously craves. The most appropriate response, and perhaps the cruelest, IMO, is to simply killfile and ignore him. An alternative, if you must, would be to post the same standard reply to his every post, listing the manifold reasons why he ought to be ignored. Just my $0.02 worth." |
#11
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Bimetalic domes
On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote:
As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I belive "Clixon" in the UK make these. -- Best Regards: Baron. |
#12
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Bimetalic domes
Baron wrote: On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote: As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I belive "Clixon" in the UK make these. That is 'Klixon', which was a division of Texas Instruments. Now it's a division of Sensata http://www.sensata.com/klixon/thermostats-thermostat.htm -- The movie 'Deliverance' isn't a documentary! |
#13
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Bimetalic domes
Michael A. Terrell wrote:
Baron wrote: On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote: As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I belive "Clixon" in the UK make these. That is 'Klixon', which was a division of Texas Instruments. Now it's a division of Sensata http://www.sensata.com/klixon/thermostats-thermostat.htm Thanks for the spelling correction and link. Its a lot of years since I played about with them. They were very popular in water heater circuits at one time. -- Best Regards: Baron. |
#14
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Bimetalic domes
On Sun, 8 Nov 2009 17:37:59 -0000, "N_Cook" wrote:
I wonder how they "weld" these 2 materials together. Probably by electroplating one of the meterials onto the other. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#15
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Bimetalic domes
Baron wrote: Michael A. Terrell wrote: Baron wrote: On Sun, 8 Nov 2009 08:42:26 -0000, "N_Cook" wrote: As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I belive "Clixon" in the UK make these. That is 'Klixon', which was a division of Texas Instruments. Now it's a division of Sensata http://www.sensata.com/klixon/thermostats-thermostat.htm Thanks for the spelling correction and link. Its a lot of years since I played about with them. They were very popular in water heater circuits at one time. They still are, but a lot of their thermal motor starters are discontinued. -- The movie 'Deliverance' isn't a documentary! |
#16
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Bimetalic domes
Explosive welding.
Simple as that. Martin N_Cook wrote: Interesting , but no further forward. Looks as though these froststats will remain froststats. Surprising ping and bounce as much as six inches on change of state, the loud ping is somewhat damped when inside the casing. Need freezer spray to change the state of these discs (hysteresis and all that). When back to body temp I tried grinding a spot in the centre of the concave side, no change in set temp. Tried 4 diametrical marks on the concave side , no change in response. Tried deeper but small 8 cuts just on the perphery, now no ping but slowly migrates from one state to the other , still requiring freezer spray. I wonder how they "weld" these 2 materials together. |
#17
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Bimetalic domes
Martin H. Eastburn wrote in message
... Explosive welding. Simple as that. Martin N_Cook wrote: Interesting , but no further forward. Looks as though these froststats will remain froststats. Surprising ping and bounce as much as six inches on change of state, the loud ping is somewhat damped when inside the casing. Need freezer spray to change the state of these discs (hysteresis and all that). When back to body temp I tried grinding a spot in the centre of the concave side, no change in set temp. Tried 4 diametrical marks on the concave side , no change in response. Tried deeper but small 8 cuts just on the perphery, now no ping but slowly migrates from one state to the other , still requiring freezer spray. I wonder how they "weld" these 2 materials together. I would have thought friction welding, probably many to a spin and then press cut to small discs |
#18
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Bimetalic domes
On Nov 8, 6:56*pm, "Martin H. Eastburn"
wrote: N_Cook wrote: I wonder how they "weld" these 2 materials together. Explosive welding. Simple as that. This might be the correct answer, but there are fill-metal/reducing atmosphere/heat solutions that might do a kind of brazing for lower cost if you get the materials right. Explosive welding is used for US coins because it was possible to mimic the electromagnetic properties of silver well enough to keep lots of vending machines in service. I've gotta believe the requirements for a thermostat bimetal system are loose enough to allow for alloys that don't require explosive welds. |
#19
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Bimetalic domes
whit3rd wrote:
On Nov 8, 6:56Â*pm, "Martin H. Eastburn" wrote: N_Cook wrote: I wonder how they "weld" these 2 materials together. Explosive welding. Simple as that. This might be the correct answer, but there are fill-metal/reducing atmosphere/heat solutions that might do a kind of brazing for lower cost if you get the materials right. Explosive welding is used for US coins because it was possible to mimic the electromagnetic properties of silver well enough to keep lots of vending machines in service. I've gotta believe the requirements for a thermostat bimetal system are loose enough to allow for alloys that don't require explosive welds. I was under the impression that two sheets of material were hot rolled together and the discs just stamped out complete with the dome shape. -- Best Regards: Baron. |
#20
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Bimetalic domes
William Wixon wrote in message
... "Baron" wrote in message ... whit3rd wrote: On Nov 8, 6:56 pm, "Martin H. Eastburn" wrote: N_Cook wrote: I wonder how they "weld" these 2 materials together. Explosive welding. Simple as that. This might be the correct answer, but there are fill-metal/reducing atmosphere/heat solutions that might do a kind of brazing for lower cost if you get the materials right. Explosive welding is used for US coins because it was possible to mimic the electromagnetic properties of silver well enough to keep lots of vending machines in service. I've gotta believe the requirements for a thermostat bimetal system are loose enough to allow for alloys that don't require explosive welds. I was under the impression that two sheets of material were hot rolled together and the discs just stamped out complete with the dome shape. -- Best Regards: Baron. how about instead of removing material from the flat surface of the dome to remove material around the outside diameter? would that alter the point at which the dome went PING? i was just wondering if the outside edge is constrained in a bezel, if there was more room to expand there if that would alter it's temperature rating? b.w. The use I see them is located fairly loosely in a well in a bakelite disc that is itself located loosely in the bakelite outer housing |
#21
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Bimetalic domes
Mark Rand wrote in message
... On Mon, 9 Nov 2009 16:13:19 -0600, "William Wixon" wrote: how about instead of removing material from the flat surface of the dome to remove material around the outside diameter? would that alter the point at which the dome went PING? i was just wondering if the outside edge is constrained in a bezel, if there was more room to expand there if that would alter it's temperature rating? b.w. If there were room, one could add a preload spring to change the set point. Mark Rand RTFM I might try that , will require adding a small well for the spring |
#22
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Bimetalic domes
N_Cook wrote:
As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I wonder if one could paint the convex face with fingernail polish as an etch resist and put the disc in an etching solution to thin the concave side? Would the relatively smaller 'concave mass' shift the trigger temperature upwards? --Winston -- On YouTube, all the tools have volume controls. |
#23
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Bimetalic domes
As used in thermal switches. Instead of in form of a bimetal strip
and continuous curving with temperature, these are 0.5" diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? Heaven knows, I don't like reinventing the wheel, but unless you can find documentation (such as a patent) that explains in detail how these devices work, and how a particular temperature is set, you're going to have to experiment. I again recommend looking for one of those interchangeable thermostats. Perhaps ripping it apart will reveal the secret! http://www.gopresto.com/products/pro...hp?stock=07211 http://www.acehardwareoutlet.com/(ua...?SKU=998000074 http://www.advertisingcookbooks.com/si/004123.html The Presto "Control Master" has been around at least 40 years, and Presto is still making appliances that use it. (I don't know whether the internal design or operating principles have changed. The probe part does appear to be longer and narrower in the current version.) |
#24
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Bimetalic domes
On Nov 8, 8:42*am, "N_Cook" wrote:
As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I have been waiting for someone to suggest that the temperature at which they switch is controlled by how domed the discs are. At least that is my guess. Suggest you get some rubber and a ballpein hammer. Test what the temperature is that one switches at, and then make in a bit more domed and see if that changed the temperature at which it switches. My guess is that more domed means more change from ambient temperature before it switches. Dan |
#25
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Bimetalic domes
wrote in message
... On Nov 8, 8:42 am, "N_Cook" wrote: As used in thermal switches. Instead of in form of a bimetal strip and continuous curving with temperature, these are 0.5 inch diameter and make a definite flip from concave to convex at a specific temperature. About 1mm of abrupt movement gives a very positive transition for the switch contacts. Would it be possible to change the characteristic temperature by grinding back a spot/ring/radii? on one face? which face? or would it just destroy the action/activation force? I have been waiting for someone to suggest that the temperature at which they switch is controlled by how domed the discs are. At least that is my guess. Suggest you get some rubber and a ballpein hammer. Test what the temperature is that one switches at, and then make in a bit more domed and see if that changed the temperature at which it switches. My guess is that more domed means more change from ambient temperature before it switches. Dan I will give it a go with large ballbearing in a cup and a press. But the full range of temp (10 to 220 deg C at least) switches all come in the same size package and the internal spaces and activation pins are the same dimensions including degree of doming, all that changes is the materials or construction within the domes. Normally open for the same temp normally closed is simply just the same dome in, the other way up |
#26
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Bimetalic domes
On Wed, 11 Nov 2009 08:49:44 -0000, "N_Cook"
wrote: wrote in message .. My guess is that more domed means more change from ambient temperature before it switches. Dan I will give it a go with large ballbearing in a cup and a press. Another thing to try is local heating and quenching in order to change the distribution of internal stresses in the dome. -- Ned Simmons |
#27
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Bimetalic domes
In article ,
Ned Simmons wrote: On Wed, 11 Nov 2009 08:49:44 -0000, "N_Cook" wrote: wrote in message . My guess is that more domed means more change from ambient temperature before it switches. Dan I will give it a go with large ballbearing in a cup and a press. Another thing to try is local heating and quenching in order to change the distribution of internal stresses in the dome. It's bimetal; I don't think you want any "unexpected" stresses. Isaac |
#28
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Bimetalic domes
--Messed around with these ages ago. The delta-T for the flip is
inversely proportional to the radius of curvature; i.e. greater radius translates to smaller temp changes to make it flip. I was working on what I call a 'kinetic solar cell' which works very well in theory... -- "Steamboat Ed" Haas : Currently broke and Hacking the Trailing Edge! : looking for a job... www.nmpproducts.com ---Decks a-wash in a sea of words--- |
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