Repaired Harbor Freight digital caliper

[Jamie]

amdx wrote:

Harbor Freight Has the 6" dial Caliper on sale 11/24

http://www.harborfreight.com/preview-thanksgiving.html?utm_medium=email&utm_campaign=4711a&utm_source=1003


Mikek
Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

 

[amdx]

On 11/21/2011 6:49 PM, Jamie wrote:

amdx wrote:
Harbor Freight Has the 6" dial Caliper on sale 11/24

http://www.harborfreight.com/preview-thanksgiving.html?utm_medium=email&utm_campaign=4711a&utm_source=1003


Mikek
Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

Do note, it is pneumatic.
Fine if your setup for it.
Mikek

 

[DoN. Nichols]

On 2011-11-21, Martin Riddle <martin_rid@verizon.net> wrote:

dagmargoodboat@yahoo.com> wrote in message
news:07d0ac35-1cf3-4ed1-ba85-cd32f2f6ea0b@p2g2000vbj.googlegroups.com...
On Nov 20, 8:45 pm, Jeff Liebermann <je...@cruzio.com> wrote:
On Sun, 20 Nov 2011 16:47:25 -0800 (PST), "Ron D." wrote:

I have a cheap Caliper too and it recently went flakey.

[ ... ]

same size. Where you can have problems is that the SR44/SR1154
silver
oxide cells come in the same package. They have about 50% more
capacity and a much flatter discharge curve. Some of the cheapo
calipers crap out below about 1.4V. The alkaline battery has plenty
of capacity left at 1.4V, but the caliper doesn't want to run. If
your caliper cames with a silver-oxide cell, it should probably use
silver oxide batteries. If it came with alkaline and has a short
battery life, it might be worthwhile trying silver-oxide. If you're
ambitious, it might be useful to run the caliper off a bench power
supply and check how low a voltage will work.

I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

So, it's clearly made for silver-oxide cells. The battery low
threshold is set appropriately for a silver oxide cell (e.g. SR-44).

It's a lousy threshold for using alkalines--they're barely broken in
at that voltage.

14.5uA means a year from a silver oxide cell--that's not horrible.

[ ... ]

Why bother including an on off switch?

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make people feel
better.

The auto-turn-off time of the display is usually good enough.

Enjoy,
DoN.

--
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Email: <BPdnicholsBP@d-and-d.com> | Voice (all times): (703) 938-4564
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[DoN. Nichols]

On 2011-11-21, dagmargoodboat@yahoo.com <dagmargoodboat@yahoo.com> wrote:

On Nov 20, 9:55 pm, "Martin Riddle" <martin_...@verizon.net> wrote:
dagmargoodb...@yahoo.com> wrote in message

news:07d0ac35-1cf3-4ed1-ba85-cd32f2f6ea0b@p2g2000vbj.googlegroups.com...




I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

[ ... ]

Why bother including an on off switch?

It's really not worth it for 1uA.

If I designed these, I'd shoot for 2uA active draw, like the
Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
The battery consumption is the biggest fault with these. Apart from
that, they're impressive.

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC. They would probably be excellent used daily in a well-illuminated
shop. In my shop, often dark for days at a time, until a project lures
me there, the replaceable batteries are a better choice.

I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge. I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there. There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently. What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes. Just put it on a stand and expect it to be fully
charged when I come back.

If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: <BPdnicholsBP@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

 

[DoN. Nichols]

On 2011-11-22, P E Schoen <paul@pstech-inc.com> wrote:

"Gunner Asch" wrote in message
news:aa0kc750e2tsad3028cqpm25aer8aus1mn@4ax.com...

Many 99c stores sell a flatpack of 5-10 standard 357 batteries
for a dollar.

I'm not sure I'd trust them in something any more expensive than a
flashlight.

Well ... I've paid more for *some* flashlights (typically
multi-LED ones) than for *some* digital calipers (import from a
hamfest), so it is a toss-up there.

I have seen them corrode and leak. And the only thing the 99
cent store might be willing to do is give you another pack or refund your
dollar.

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small zip-loc
baggie, so they don't damage anything else when leaking.

FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in anything
in which I have used them.

Enjoy,
DoN.

--
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Email: <BPdnicholsBP@d-and-d.com> | Voice (all times): (703) 938-4564
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[P E Schoen]

"DoN. Nichols" wrote in message
news:slrnjclve8.op3.BPdnicholsBP@Katana.d-and-d.com...

On 2011-11-21, Martin Riddle <martin_rid@verizon.net> wrote:

Why bother including an on off switch?

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make
people feel better.

The auto-turn-off time of the display is usually good enough.

Still, there's no benefit to turning off the display, in this case. Might
just as well have it display "OFF".

I bought a high-end headlamp from Coleman a few years ago
http://www.coleman.com/coleman/ColemanCom/detail.asp?CategoryID=1116&product_id=2000000265#
and every time I went to use it the batteries (4 AA) were dead. I measured
the current draw when turned off, and it was something like 300 uA, which
should have provided 8000 hours (almost one year) for the 2500 mA-hr
batteries. But I was getting only a few weeks before finding them exhausted.
Maybe the current increased as the battery voltage dropped. I usually used
rechargeable NiMH and they might have been old and tired. But, still, there
is no reason for 300 uA standby current on a flashlight. Even if it had a
microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
while I'm not using it. There's no easy place to install a switch.

Paul
www.muttleydog.com

 

[P E Schoen]

"DoN. Nichols" wrote in message
news:slrnjcm1ee.op3.BPdnicholsBP@Katana.d-and-d.com...

Well ... I've paid more for *some* flashlights (typically
multi-LED ones) than for *some* digital calipers (import
from a hamfest), so it is a toss-up there.

Yes, the Coleman headlamp I mentioned elsewhere lists for $50, and I paid
probably $20 on clearance, so I agree, in that case. But most flashlights
with coin cells are pretty much disposable.

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small
zip-loc baggie, so they don't damage anything else when leaking.

That's what I am going to do. There is a cutout in the foam of the caliper
case for a spare. I also put the other three cells in their original
packaging in there. I plan to use the calipers more now that I can depend on
them (and know how to fix them). Usually I don't do much precision
machining, and I have a cheap plastic dial caliper that is good to about
0.01" and is immune to humidity and most abuse.

FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in
anything in which I have used them.

I think the original cell in the HF caliper was actually alkaline, and
fortunately I had removed it (but kept in the case) when I had tried to fix
them a few years ago with no joy. When I opened it recently, the cell was
rusty and there was some liquid that had oozed out. I've also had some NiMH
AA cells that leaked. But probably the silver cells are better made and the
chemicals may be less aggressive. Now that I've found an on-line source with
good pricing I think I'll stick with them, although it's tempting to get the
Chinese copies for 10 cents each.

Paul

 

On Nov 21, 9:08 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:

On 2011-11-21, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:

On Nov 20, 9:55 pm, "Martin Riddle" <martin_...@verizon.net> wrote:
dagmargoodb...@yahoo.com> wrote in message

news:07d0ac35-1cf3-4ed1-ba85-cd32f2f6ea0b@p2g2000vbj.googlegroups.com....

I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

        [ ... ]

Why bother including an on off switch?

It's really not worth it for 1uA.

If I designed these, I'd shoot for 2uA active draw, like the
Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
The battery consumption is the biggest fault with these.  Apart from
that, they're impressive.

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

        Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC.  They would probably be excellent used daily in a well-illuminated
shop.

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted. Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

OTOH, I paid $10 for most of my HF calipers. Those you can take
chances with. Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

I fitted one to the lathe carriage--best thing I ever did.
Removable. I fitted another to the tailstock ram. With it you can
bore to 0.002" depth every time without even trying. Magic.

 In my shop, often dark for days at a time, until a project lures
me there, the replaceable batteries are a better choice.

        I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge.  I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there.  There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently.  What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes.  Just put it on a stand and expect it to be fully
charged when I come back.

        If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight.

Sounds like a LiIon cell. If so, those can't be allowed to go dead,
as you've surmised.

--
Cheers,
James Arthur

 

On Nov 21, 9:34 pm, "P E Schoen" <p...@pstech-inc.com> wrote:

"DoN. Nichols"  wrote in message

news:slrnjclve8.op3.BPdnicholsBP@Katana.d-and-d.com...

On 2011-11-21, Martin Riddle <martin_...@verizon.net> wrote:
Why bother including an on off switch?
It is an off switch to turn the *display* (only) back on.  They
sometimes make it also turn the display back off to make
people feel better.
The auto-turn-off time of the display is usually good enough.

Still, there's no benefit to turning off the display, in this case. Might
just as well have it display "OFF".

I bought a high-end headlamp from Coleman a few years agohttp://www.coleman.com/coleman/ColemanCom/detail.asp?CategoryID=1116&...
and every time I went to use it the batteries (4 AA) were dead. I measured
the current draw when turned off, and it was something like 300 uA, which
should have provided 8000 hours (almost one year) for the 2500 mA-hr
batteries. But I was getting only a few weeks before finding them exhausted.
Maybe the current increased as the battery voltage dropped. I usually used
rechargeable NiMH and they might have been old and tired. But, still, there
is no reason for 300 uA standby current on a flashlight. Even if it had a
microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
while I'm not using it. There's no easy place to install a switch.

Paulwww.muttleydog.com

I measured some ordinary NiMH cells' self-discharge, 1,600mAH, @ 1.6mA
IIRC. The high-capacity rechargeables are wickedly worse. I've got
one set that won't hold a charge much over two weeks, no kidding,
even brand-new. Self-discharge current on the order of 5-7mA.

There are low-self-discharge NiMH that hold a charge much longer,
sometimes up to a year. Highly recommended. Ray-O-Vac Hybrids, Sanyo
Eneloop, and Duracell has some too.

--
Cheers,
James Arthur

 

[Gunner Asch]

On Mon, 21 Nov 2011 19:32:51 -0500, "P E Schoen" <paul@pstech-inc.com>
wrote:

I just purchased four genuine SR44s from an eBay store, for $3, including
first class mail shipping. The same company also has larger packs for quite
a bit less.
http://stores.ebay.com/RL-batterydepot?_trksid=p4340.l2563

Thanks!!!

Ill check em out and stock up!!

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

 

[Michael A. Terrell]

P E Schoen wrote:

I've also had some NiMH AA cells that leaked.

I have the control panel & 'Rabbit Semiconductor' RCM2000 computer
board from an Ineco Basic tubing bender that was damaged by a leaking
3.6 V 80 mAh NiMH battery. That leak cost a local business $700 for a
failed $5 battery. The tool was eight years old. I called them
yesterday and told them to log the date the board was installed, and to
have me replace it in two years as PM. The symptoms were that the
machine started bending the wrong angles, and different angles without
changing the setup. A trace below the battery was eaten by the leaking
chemicals. I'll try to get a good photo before I return it to them. It
might save someone else a wad of cash, or convince a shop owner to let
you check for leaking batteries. The machine was used on a regular
business, a few days per week, so it wasn't caused by long term storage.


--
You can't have a sense of humor, if you have no sense.

 

[Jim Yanik]

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:m80lc75dhftjsj5n4lqdcm9m1actgfu290@4ax.com:

On Mon, 21 Nov 2011 10:36:03 -0600, Jim Yanik <jyanik@abuse.gov
wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:ff9jc7h30fqjm073j6k38tic1cj6pg51jk@4ax.com:


Homebrew cleaners and protectors:
http://www.pitt.edu/~szekeres/cleaner.htm
The comments on the effects of silicones plus salt in WD40 are
interesting.


WD-40 is mostly kerosene.

Close. It's mostly Stoddard Solvent, also known as mineral spirits.
http://www.snopes.com/inboxer/household/wd-40.asp
http://en.wikipedia.org/wiki/WD-40
http://en.wikipedia.org/wiki/Stoddard_solvent
50% Stoddard solvent (i.e., mineral spirits: primarily hexane,
somewhat similar to kerosene)
25% Liquefied petroleum gas (presumably as a propellant; carbon
dioxide is now used instead to reduce WD-40's considerable
flammability)
15+% Mineral oil (light lubricating oil)
10-% Inert ingredients

Reverse engineering at its best:
http://www.wired.com/science/discoveries/magazine/17-05/st_whatsinside

USA MSDS sheet:
http://www.wd40company.com/files/pdf/msds-wd494716385.pdf

The key ingredient is a sulfactant (wetting agent), to reduce surface
tension and make it "cling" to objects and "puddle" water. My
guess(tm) the reason it took 40 trys is that they had a difficult time
finding one that would work in a solvent solution.

I'd not go by Wikipedia,I'd go by the actual WD-40 MSDS.
if you read the MSDS -for each ingredient- listed for WD-40 on the WD-
40 MSDS(like I did),you'll see that it's mostly kerosene.

--
Jim Yanik
jyanik
at
localnet
dot com

 

[Dave Platt]

In article <Xns9FA57C50659FCjyaniklocalnetcom@216.168.3.44>,
Jim Yanik <jyanik@abuse.gov> wrote:

USA MSDS sheet:
http://www.wd40company.com/files/pdf/msds-wd494716385.pdf

The key ingredient is a sulfactant (wetting agent), to reduce surface
tension and make it "cling" to objects and "puddle" water. My
guess(tm) the reason it took 40 trys is that they had a difficult time
finding one that would work in a solvent solution.



I'd not go by Wikipedia,I'd go by the actual WD-40 MSDS.
if you read the MSDS -for each ingredient- listed for WD-40 on the WD-
40 MSDS(like I did),you'll see that it's mostly kerosene.

I don't see either kerosene, or Stoddard solvent, by name in the MSDS.

Rather, I see "Aliphatic hydrocarbon" (CAS #64742-47-8) as the
ingredient with the highest concentration. Commonest synonym seems to
be "Hydrotreated light petroleum distillates." Usable as fuel oil or
solvent.

If I understand correctly, all of these petroleum distillates form a
continuum - most are mixtures of hydrocarbons with differing molecular
weights. I don't think there's a sharp physical cutoff between what
constitutes a "kerosene" and a "solvent" - it's all a matter of
convention.

According to the MSDS, WD-40 is a bit more than half solvent (about an
eighth is "LVP", presumably slower to evaporate?), about a quarter
light lubricating oil, a couple of percent of the secret-sauce
surfactant that Jeff was alluding to, CO2 for pressurization, and 10%
mixed "non-hazardous ingredients."

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Jeff Liebermann]

On Tue, 22 Nov 2011 11:30:34 -0800, dplatt@radagast.org (Dave Platt)
wrote:

In article <Xns9FA57C50659FCjyaniklocalnetcom@216.168.3.44>,
Jim Yanik <jyanik@abuse.gov> wrote:

USA MSDS sheet:
http://www.wd40company.com/files/pdf/msds-wd494716385.pdf

The key ingredient is a sulfactant (wetting agent), to reduce surface
tension and make it "cling" to objects and "puddle" water. My
guess(tm) the reason it took 40 trys is that they had a difficult time
finding one that would work in a solvent solution.



I'd not go by Wikipedia,I'd go by the actual WD-40 MSDS.
if you read the MSDS -for each ingredient- listed for WD-40 on the WD-
40 MSDS(like I did),you'll see that it's mostly kerosene.

I don't see either kerosene, or Stoddard solvent, by name in the MSDS.

Rather, I see "Aliphatic hydrocarbon" (CAS #64742-47-8) as the
ingredient with the highest concentration. Commonest synonym seems to
be "Hydrotreated light petroleum distillates." Usable as fuel oil or
solvent.

If I understand correctly, all of these petroleum distillates form a
continuum - most are mixtures of hydrocarbons with differing molecular
weights. I don't think there's a sharp physical cutoff between what
constitutes a "kerosene" and a "solvent" - it's all a matter of
convention.

According to the MSDS, WD-40 is a bit more than half solvent (about an
eighth is "LVP", presumably slower to evaporate?), about a quarter
light lubricating oil, a couple of percent of the secret-sauce
surfactant that Jeff was alluding to, CO2 for pressurization, and 10%
mixed "non-hazardous ingredients."

Well, let's dive a bit deeper into the contents. The CAS number
identifies the exact ingredients. We have:
CAS % by weight
Aliphatic Hydrocarbon 64742-47-8 45-50%
That would be:
<http://www.cdc.gov/niosh/ipcsneng/neng1379.html>
Low odor paraffinic solvent, Dearomatized kerosine, Deodorized
kerosene. In other words, lamp oil as used in a kerosene lamp.

Petroleum Base Oil <25%
64742-58-1 Recycled motor oil
64742-53-6 Distillates(petroleum), hydrotreated light naphthenic.
Also known as Coleman fuel
64742-56-9 Solvent-dewaxed light paraffinic.
64742-65-0 Solvent-dewaxed heavy paraffinic.

LVP Aliphatic Hydrocarbon 12-18%
64742-47-8 Same as the first item. Kerosene.
My guess is that LVP means "low vapor pressure" which for solvents
means that it's slow to evaporate.

(gotta run...)

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

 

[DoN. Nichols]

On 2011-11-22, dagmargoodboat@yahoo.com <dagmargoodboat@yahoo.com> wrote:

On Nov 21, 9:08 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:
On 2011-11-21, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:

[ ... ]

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

        Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC.  They would probably be excellent used daily in a well-illuminated
shop.

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted. Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

I've seen them only new, and decided that in my shop conditions,
they would not work very well.

OTOH, I paid $10 for most of my HF calipers. Those you can take
chances with. Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

O.K. Do you know the maximum voltage that the solar panel is
likely to produce? And the voltage drop on the LED? I know that
silicon diodes are typically between 600 mV and 750 mV. Also, any clues
as to the maximum voltage that the calipers can tolerate long term?

[ ... ]

        I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge.  I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there.  There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently.  What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes.  Just put it on a stand and expect it to be fully
charged when I come back.

        If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight.

Sounds like a LiIon cell. If so, those can't be allowed to go dead,
as you've surmised.

And -- they are supposedly not replaceable according to the
manual. (You've got to cut the package apart to get to them.) There
is a web page describing how someone opened one up and set a holder for
two AA cells outside the package. I'm really tempted to go for the
induction charger when I finally have to dig into mine. But it is
significantly less expensive than auto-darkening ones from MSC -- to the
point where three HF ones match the cost of one from MSC.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: <BPdnicholsBP@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

 

[DoN. Nichols]

On 2011-11-22, P E Schoen <paul@pstech-inc.com> wrote:

"DoN. Nichols" wrote in message
news:slrnjcm1ee.op3.BPdnicholsBP@Katana.d-and-d.com...

[ ... ]

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small
zip-loc baggie, so they don't damage anything else when leaking.

That's what I am going to do. There is a cutout in the foam of the caliper
case for a spare. I also put the other three cells in their original
packaging in there. I plan to use the calipers more now that I can depend on
them (and know how to fix them). Usually I don't do much precision
machining, and I have a cheap plastic dial caliper that is good to about
0.01" and is immune to humidity and most abuse.

Except for certain solvents.

Good Luck,
DoN.

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On Nov 22, 9:21 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:

On 2011-11-22, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted.  Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

        I've seen them only new, and decided that in my shop conditions,
they would not work very well.

OTOH, I paid $10 for most of my HF calipers.  Those you can take
chances with.  Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

        O.K.  Do you know the maximum voltage that the solar panel is
likely to produce?  And the voltage drop on the LED?  I know that
silicon diodes are typically between 600 mV and 750 mV.  Also, any clues
as to the maximum voltage that the calipers can tolerate long term?

The max. solar panel voltage doesn't matter--the LED regulator clamps
the solar panel voltage, taking care of that.

Here's a sketch:

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~>
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper


C1 - A capacitor to power the caliper during momentary outages.
Optionally a super-cap., e.g. http://www.goldmine-elec-products.com/prodinfo.asp?number=G13133
(Note1: The PV will take HOURS of bright light to charge a super-
cap, so you might want to precharge the cap, then let the PV just
float it.)
(Note2: Super-caps have significant electrical leakage. If your
cap is too leaky, it'll never charge, and you'll be disappointed. I
haven't measured the above-linked PAS920 to see if this is the case.)

PV - http://www.goldmine-elec-products.com/prodinfo.asp?number=G17448,
or, stolen from the cheapest solar-powered calculator you can find.
Walmart and the dollar stores have some good candidates.
LED - shunt-regulates the PV output to a safe voltage.
D1 - 1n4148, prevents PV from draining a super-cap C1 when dark,
possibly not needed. (Depends on PV panel's dark leakage current.)


To set the voltage you'd choose an LED with a forward voltage of, say
1.6-1.8v. Three ordinary small-signal silicon diodes in series (e.g.
1n4148) wouldn't be a bad choice either. With surface-mount parts,
the ckt can be tiny.

If the voltage is too high it's not a matter of "long-term," the
caliper will die instantly. I don't know what that voltage is, but
I'd easily wager one of *my* $10 calipers that 2v is okay, and I'd
wager one of *yours* that 2.5v might be okay too. ;-)

--
Cheers,
James Arthur

 

[Bob Engelhardt]

dagmargoodboat@yahoo.com wrote:
....

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper

....

Doncha' need a current limiter on the LED?

Bob

 

[John S]

On 11/23/2011 2:05 PM, Bob Engelhardt wrote:

dagmargoodboat@yahoo.com wrote:
...

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper

...

Doncha' need a current limiter on the LED?

Bob

Not if the PV cell's rated SC current is less than the max LED current
rating.

 

[Winston]

Bob Engelhardt wrote:

dagmargoodboat@yahoo.com wrote:
...

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper

...

Doncha' need a current limiter on the LED?

Nup. It's a 'shunt regulator'.
http://en.wikipedia.org/wiki/Linear_regulator#Simple_zener_regulator

--Winston