I've got a problem for you ;-)

[Jim Thompson]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (°F) when the real range
was 40 to 65 °F.

I was pondering an electronic replacement with some kind of
low-powered indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

Thanks!

...Jim Thompson

 

[John Woodgate]

I read in sci.electronics.design that Jim Thompson

I was pondering an electronic replacement with some kind of low-powered
indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

Isn't this a job for an LM 35? I don't know where you could get an LCD
that simulates a pointer meter, though.

 

[Spehro Pefhany]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (°F) when the real range
was 40 to 65 °F.

I was pondering an electronic replacement with some kind of
low-powered indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

There are some chips (eg. Philips) available to drive air-core
indicator coils. Or you could probably scavenge a DC tachometer meter
movement from somewhere. Then just one of those little National
temperature sensor chips and an op-amp. It wouldn't operate for a year
from a battery or anything, most meter movements need 100uA or so. A
stepper motor would consume no power when not actually moving, that's
one possibility. This kind of thing is used in some process control
instrumentation becuase it will stand up to earthquakes (eg. for
nuclear plants). Maybe an 4000 CMOS up/down counter, R2R ladder
low-power DAC?

Not to spoil your fun, but you can get 1-7/16" gold color bezel
bimetal thermometers for just a few dollars.

Best regards,
Spehro Pefhany

 

[jmagerl]

maybe www.klockit.com ?

 

[Jim Thompson]

There are some chips (eg. Philips) available to drive air-core
indicator coils. Or you could probably scavenge a DC tachometer meter
movement from somewhere. Then just one of those little National
temperature sensor chips and an op-amp. It wouldn't operate for a year
from a battery or anything, most meter movements need 100uA or so. A
stepper motor would consume no power when not actually moving, that's
one possibility. This kind of thing is used in some process control
instrumentation becuase it will stand up to earthquakes (eg. for
nuclear plants). Maybe an 4000 CMOS up/down counter, R2R ladder
low-power DAC?

Not to spoil your fun, but you can get 1-7/16" gold color bezel
bimetal thermometers for just a few dollars.

Best regards,
Spehro Pefhany

Spehro,

I have a 6" pointer that indicates temperature over a 270° arc for
-40°F to +120°F

This is carved-in-stone out on the patio upon which you and your wife
have set and is under the jurisdiction of the management ;-)

Thus "hack" jobs are impermissible.

I vaguely remember a thirty-year-ago project that used some kind of
two-coil indicator (Stewart-Warner).

These don't move when un-powered.

What I had in mind is powering up every 15 minutes, apply power to the
coils to set the current temperature, then sleep again for 15 minutes
(or whatever is necessary).

Temperature measurement has been a good chunk of my career... that's
the easy part... getting the indicator mechanism will be a wee bit
more difficult.

Or maybe there's a bi-metal indicator out there that has adjustable
end-points ??

...Jim Thompson

 

[Boris Mohar]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (°F) when the real range
was 40 to 65 °F.

Pointer sticking at 0° ?

 

[Mark J.]

In news:[email protected] (Jim Thompson):

Spehro,

I have a 6" pointer that indicates temperature over a 270° arc for
-40°F to +120°F

This is carved-in-stone out on the patio upon which you and your wife
have set and is under the jurisdiction of the management ;-)

Thus "hack" jobs are impermissible.

I vaguely remember a thirty-year-ago project that used some kind of
two-coil indicator (Stewart-Warner).

These don't move when un-powered.

What I had in mind is powering up every 15 minutes, apply power to the
coils to set the current temperature, then sleep again for 15 minutes
(or whatever is necessary).

Temperature measurement has been a good chunk of my career... that's
the easy part... getting the indicator mechanism will be a wee bit
more difficult.

Or maybe there's a bi-metal indicator out there that has adjustable
end-points ??

...Jim Thompson

Heat up the bi-metal and temper/anneal/harden it?

 

[Jim Thompson]

maybe www.klockit.com ?

[snip]

Thanks for the tip! I have sent them an E-mail to see if they have a
replacement mechanism.

...Jim Thompson

 

[Spehro Pefhany]

I have a 6" pointer that indicates temperature over a 270° arc for
-40°F to +120°F

This is carved-in-stone out on the patio upon which you and your wife
have set and is under the jurisdiction of the management ;-)

Say no more. Hmm, okay given that, check out #5310 & 5353 here:
http://www.branom.com/COMPANIES/taylor.html

Thus "hack" jobs are impermissible.

I vaguely remember a thirty-year-ago project that used some kind of
two-coil indicator (Stewart-Warner).

Stewart-Warner is *the* keyword for the raw movements themselves,
AFAIUI.

Drivers for this type of very linear indicator:

http://www.semiconductors.philips.com/acrobat/applicationnotes/AN1761.pdf
http://www.semiconductors.philips.com/acrobat/datasheets/SA5775A_3.pdf
http://moon.feld.cvut.cz/hw/philips/acrobat/5027.pdf
http://cache.national.com/ds/LM/LM1819.pdf (discontinued)
http://www.nteinc.com/specs/1600to1699/pdf/nte1670.pdf
http://www.onsemi.com/pub/Collateral/CS8190-D.PDF
http://www.onsemi.com/pub/Collateral/CS4121-D.PDF

Possible source for a movement (but looks more like 240° than 270°)
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33679&item=2456769547

These don't move when un-powered.

What I had in mind is powering up every 15 minutes, apply power to the
coils to set the current temperature, then sleep again for 15 minutes
(or whatever is necessary).

Temperature measurement has been a good chunk of my career... that's

I'll wager even more of mine, but this is about as easy as they come!

the easy part... getting the indicator mechanism will be a wee bit
more difficult.

Or maybe there's a bi-metal indicator out there that has adjustable
end-points ??


...Jim Thompson

Best regards,
Spehro Pefhany

 

[Jim Thompson]

Pointer sticking at 0° ?

What's "0"? That's plus 40°F. I've not experienced 0°F EVER in
Phoenix ;-)

...Jim Thompson

 

[Mark Fergerson]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (°F) when the real range
was 40 to 65 °F.

I was pondering an electronic replacement with some kind of
low-powered indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

Wrong repair paradigm. Unless the bimetal element has
been heated or corroded so that it's incapable of reading
correctly, it's just slipped a bit in its moorings. Look in
the back for a little bitty adjustment screw with a locknut.

Probably best to set it while the ambient temp is at its
midrange.

Mark L. Fergerson

 

[Spehro Pefhany]

Wrong repair paradigm. Unless the bimetal element has
been heated or corroded so that it's incapable of reading
correctly, it's just slipped a bit in its moorings.

Note the "span" shift that Jim reports.. it's more than a "zero"
offset.

Best regards,
Spehro Pefhany

 

[jim]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (°F) when the real range
was 40 to 65 °F.

I was pondering an electronic replacement with some kind of
low-powered indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

Thanks!

...Jim Thompson

i got a plate with a clock in the middle of it at the dollars stores and
took the clock out of it to replace it inside someother piece of junk
clock we have/had??? did never find any temperature stuff in the dollar
stores, you might just throw it out if you cannot fix it or keep it in
storage and your kids can throw it out when they have to go through your
stuff...

 

[Chuck Harris]

Hi Jim,

Although it is rare for a bimetal that isn't corroded to fail,
you can get replacements for many different types from:

http://www.slarose.com

Let them know what the diameter, the temperature range, and the
dial type (eg 270degree, 60 degree, etc..) and anything else you
can think to describe, and they will let you know what matches.

Typical price of these kinds of things is under $5.

-Chuck Harris

 

[Bill Garber]

: Hi Jim,
:
: Although it is rare for a bimetal that isn't corroded to fail,
: you can get replacements for many different types from:
:
: http://www.slarose.com
:
: Let them know what the diameter, the temperature range, and the
: dial type (eg 270degree, 60 degree, etc..) and anything else
you
: can think to describe, and they will let you know what matches.
:
: Typical price of these kinds of things is under $5.
:
: -Chuck Harris

This ain't 1923, take a pic of the bimetal coil
and email it to them. I'm sure if they see it they
can match it much more readily.

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - [email protected]
Remove - SPAM and X to contact me

 

[DarkMatter]

I have a sandstone (American aboriginal) Indian carving with a clock
and a bi-metal (rotating pointer) thermometer in it.

I was able to find a replacement battery-powered clock mechanism.

But I've had no luck with replacing the bi-metal thermometer.

It's completely hosed... indicates 0 to +65 (?F) when the real range
was 40 to 65 ?F.

I was pondering an electronic replacement with some kind of
low-powered indicator (such as the fuel gauges in old GM products).

Any ideas... design, procurement, etc.?

Thanks!

There are a lot of them in regular Dept. stores in humi / temp
combos.

 

[DarkMatter]

Temperature measurement has been a good chunk of my career... that's
the easy part... getting the indicator mechanism will be a wee bit
more difficult.

Or maybe there's a bi-metal indicator out there that has adjustable
end-points ??

As long as you can get the 270 degrees of arc, you could copy the
scale from the procured unit to the unit in question. The needle will
work, regardless of it's length (without extreme exaggerations that
is).

 

[Martin Riddle]

Some one does make a psueado LCD meter that has an analog look to it. Comes in colors too.
But I can find it at the moment.

I would stick with the mechanical style tho. Maybe check process control oriented distributors.
Or even photo equipment suppliers (darkroom). You might find a suitable replacement that way.
Even all stainless.

Cheers

 

[Jim Thompson]

Some one does make a psueado LCD meter that has an analog look to it. Comes in colors too.
But I can find it at the moment.

I would stick with the mechanical style tho. Maybe check process control oriented distributors.
Or even photo equipment suppliers (darkroom). You might find a suitable replacement that way.
Even all stainless.

Cheers

[snip]

How ya going to do that in the front of a stone carving?

I need a rotating pointer.

...Jim Thompson

 

[Jeff]

There are some chips (eg. Philips) available to drive air-core
indicator coils. Or you could probably scavenge a DC tachometer meter
movement from somewhere. Then just one of those little National
temperature sensor chips and an op-amp. It wouldn't operate for a year
from a battery or anything, most meter movements need 100uA or so. A
stepper motor would consume no power when not actually moving, that's
one possibility.

A good stepper for this application could come from an old 3.5" floppy
drive! Put a stop on the dial, rotate the stepper enough steps to rotate
fully CCW from any postion, to set the pointer into a known pstion, and
count the right number of steps CW to indicate the temperature. Have the
pointer restet it's self every so often. It could be easily done with a AVR
tiny, using the built in A/D to get a temperature reading, and a port to
directly drive the stepper. The tempeature could be mapped in software, and
few lines of code could control it.

This kind of thing is used in some process control
instrumentation becuase it will stand up to earthquakes (eg. for
nuclear plants). Maybe an 4000 CMOS up/down counter, R2R ladder
low-power DAC?

Not to spoil your fun, but you can get 1-7/16" gold color bezel
bimetal thermometers for just a few dollars.

Best regards,
Spehro Pefhany

http://www.speff.com