Battery eliminator for digital caliper

I couldn't resist this as an easy quick-a-minnit project.
It's a way to connect an external 1.5 volt supply to a digital
caliper, as in those used as DRO's on mills and so forth.
Means for holding the "battery" in place are left to the user's
imagination. I'll note that I have one caliper that has used duct
tape to hold the battery in place for years, one small piece of new
duct tape per battery change.
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Reply to
Don Foreman
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WHAT? no strain relief?
I'll only give you a 9.5 for leaving that off.
My last "5 minute job" a couple of weeks ago (Taking more like 45 minutes by the time I got done varnishing the handle.) was making a menorah candle holder reamer. It's just a crude hand forged 5/16" diameter spade bit epoxied into a piece of dowel.
I got tired of picking away with the point of a steak knife removing the bits of wax and wick from those little 5/16" diameter candleholders so we could insert new candles for the next of the eight nights of Hanukkah, which is appropriately called "The festival of lights".
Having to clean a total of 44 burnt out candle ends over the week long holiday made the project justifiable, as I didn't have a stubby screwdriver I was willing to part with and convert for that purpose.
Happy New Year,
Jeff
Reply to
Jeff Wisnia
A 2 conductor pair pulled from a ribbon cable would be much more compact and might allow the cover to be used with mods. JR Dweller in the cellar
D> I couldn't resist this as an easy quick-a-minnit project.
Reply to
JR North
Didn't have the duct tape on in the photo.
Reply to
Don Foreman
Good idea. Another noted that the center lead could be brought out the side of the "cell". On this particular caliper (HF), there is a gap in the battery well (visible in the photo) that would pass such a side-mounted pair of wires, and the cover would still stay on if a bit of it was removed to pass the wires.
Mark II is always different (and sometimes better) than Mark I!
Reply to
Don Foreman
Thats way too easy. I'm thinking unwind a small transformer and wind a tiny coil, then stuff it and a tiny surface mount rectifier, capacitor and voltage regulator inside the battery compartment, then wind a larger coil around and tape it to the outside of the battery door and send pulsing DC or AC through the outside coil to inductively power the inner coil. That should cost 10 times more than the cost of the batteries it would have used in its whole life and take at least a few days to design, build, and debug making it a successful project.
Reply to
Eugene
For those who don't know, the little door above the battery compartment shown in the third photo has a 4 pin connector two pins of which are for external power when these are used with electronic readouts. To improve noise immunity you should replace the battery with a small capacitor.
Reply to
Mike Swift
That'll work -- if you have a suitable connector.
Reply to
Don Foreman
OK, I'll bite on this one:
Do you have a dead electric toothbrush that charges with a cradel and no exposed contacts? Could this be used somehow as a power source?
Charles Friedman DDS Ventura by the Sea New Years wishes to all
Reply to
Charles Friedman
It certainly could, but the pickup coil and elex would be considerably larger than a faux 357 cell with wires -- or a suitable connector into the SPC port as suggested by JR North.
Reply to
Don Foreman
Don, very nice work, as always. Note that some calipers use batteries much more sparingly.
i
Reply to
Ignoramus11124
Oops, shoulda said as suggested by Mike Swift.
Reply to
Don Foreman
I would stay away from digital calipers with power supplies like these. They are working capacitive and you don't want to induce voltages into the capacitor arrays.
Nick
Reply to
Nick Mueller
Peltier effect (actually Seebeck effect, in this direction) generator fixed to the case so that when you pick up the caliper, you power it with the heat of your hand....
:-)
Mark Rand RTFM
Reply to
Mark Rand
On my generic Chinese digital caliper - which seems to be pretty typical of the kind that people are using for DROs - the battery contacts are brought out to the data interface connector (a 4 way edge connector), so it's easy to just power it from your controller. The one 'gotcha' is the potential for the cable to pick up noise/hum & confuse the measurement electronics in the caliper. When I convert mine, I'll most likely put in a series resistor, an LED as a ~1.5V shunt regulator, & a pair of small caps (10uF tantalum, 0.47uF monobloc ceramic) to simulate a battery.
If your caliper starts giving whacky readings when you wire it up to something, or power it with something other than the standard button cell, you also need a little circuit like this. If anyone else wants one, say so here, & I'll draw up a schematic for y'all.
Yep, same as mine.
Cute little adapter, too. Personally, I'd just solder some instrument cable to the terminals, but then I do more electronics work than metalwork anyway. ;)
Reply to
Lionel
Nice idea, but the stray field from the coil would send the caliper electronics into epilectic fits. If you're determined to go to that much trouble, you'd be better off with a little solar cell (one ratted from one of those throwaway solar powered calculators would be ideal), combined with a little tantalum capacitor to filter out the ripple from your workshop lights.
Reply to
Lionel
I frequently use my bulk tape eraser to demagnetize my watchmakers lathe and cheapie caliper - no problem so far... /mark
Li>
Reply to
Mark F
This started out with an inquiry by Karl, who doesn't like soldering teensy stuff. I can drop the little adapter in an envelope and mail it to him with one stamp -- he'll have to supply the duct tape. The little LM317-based regulator can be located very nearby -- it'd just be a gob about the size of an acorn in the wires.
Reply to
Don Foreman
Geeezzzz, Don.... what I *really* expected from you would have been a *miniature* hit n miss engine powering a small generator (DC of course)..... all fitting in the space the original battery filled..... :) Ken.
Reply to
Ken Sterling
I'm waiting for Bob Swinney to show us his steam engine (with nanoboiler) that fits in a 357 battery compartment.
Reply to
Don Foreman

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