digital caliper battery drain

[Beo]

Got frustrated with my digital caliper battery always being dead when I need it. So to the google machine, and found this link:
https://www.sparkfun.com/tutorials/362

Tutorial shows how to wire up an AAA battery holder for much longer battery life. Comments had a good suggestion about wiring up a micro slide switch to break the battery wire. Time to DIY modify my DIY tools. (hmm... if I had to mod my soldering iron, how would I solder it?)

[Phoenix]

Funny you mention modding a soldering iron, I did that to my Hakko clone recently. I added a mains earth referenced 4mm banana socket for connecting my ESD mat, which is much more convenient that the power socket connection I was using before.
I also added a three position switch for the tip grounding, either "hard" earth, "soft" earth (through a 1Meg resistor), or floating. This allows standard-duty, working on ESD sensitive circuits, or the very rare occasion where I need to work on "live" equipment. I did this mod about three months ago and haven't needed to use that feature yet (and I repair full-time for a living, so definitely not advocating that technique).

Fortunately I have a few soldering irons, so that made the process straight-forward.

[R.G.]

Got frustrated with my digital caliper battery always being dead when I need it.

Very odd. I have four sets of digital calipers, and have for years. I use them all the time. I've replaced, as I remember, three batteries in the four calipers in ten years. I wonder if the newer ones eat more current. Could be, I guess.

I have a set of dial calipers with the same resolution just in case.   

[Phoenix]

Very odd. I have four sets of digital calipers, and have for years. I use them all the time. I've replaced, as I remember, three batteries in the four calipers in ten years. I wonder if the newer ones eat more current. Could be, I guess.

Cheaper ones often have very high standby current draw, of the same order-of-magnitude as operating current.
Here's a video that goes into some detail:

[Gus]

I have 6 of the digital calipers you can find on sale for about $10. dollars.  One will discharge the battery so I remove when not in use.

[samhay]

I take the battery out of mine when I am not using them. Problem is that the battery door and/or batter pads don't stand up to this wear for terribly long (only a few years each). Have been meaning to mount an AAA battery to a broken set, so might give it a try and report back.

Edit - here we go:



Single AAA holder (from Maplin) mounted to the calipers. You lose the ability to lock the calipers, but they feel ok in the hand and after a little trimming (of the case foam), they still fit in the case.
There is just enough clearance to use the top gauges to measure e.g. hole diameters.

[paulo.morato]

Hi,

My name is Paulo and I'm from Sao Paulo, Brazil.

I have one that cheap caliper and I am frustrated with battery consumption too. My solution for this is a latch mosfet switch. I have cut all original traces of power push button. The switch consumption is ~6uA, caliper ~17uA (on or off) in original state. After modification 24uA ON and 0.013uA OFF (Keithley 196A).

This is a LTSpice diagram and MYSW is a push switch simulation. R1 and R2 = 470k



Caliper uses CR2032 cell:



Caliper board. I cut power trace:



The mosfet switch. I will modify push button wires to pass around sensor traces:



Latch switch with protect silicon:

[marcelomd]

Bem vindo, Paulo,

That is what hacking is about. Nice project. Also very tidy.

Abraço de Porto Alegre =)

[paulo.morato]

Olá Marcelo,

Thanks!

[amz-fx]

I remove the battery from my digital calipers because I had a battery leak while the tool was stored in its case.

Fortunately I caught it quickly and was able to clean the goop from the inside of the battery compartment before it did any lasting damage. So now I always take out the battery once I am through making measurements.

Best regards, Jack