# Digital Z scale



## Noitoen (Dec 27, 2009)

The other day I bought a cheap plastic 150mm/6In digital calliper for 8,00 with the intention to mount it on my Optimum F45 mill as a Z axis gauge. It has a total course of 120mm and it looked just right for the job. It was the first calliper I saw that works in mm, inches (decimal) and inches (fractions)  Sorry about the picture quality as the mobile phone's camera and poor lighting conditions don't mix well.


----------



## Kermit (Dec 27, 2009)

If that's the one I think it is, then you will be eating batteries left and right. Good job on the mounting fixture by the way. That's the way I hope to mount one on mine eventually.

after you replace those batteries a few times look at alliedelec.com or jameco.com for a proper plug in supply to replace those batteries. You could hard wire it to the electrics inside the mill to avoid the wires on the outside...

Kermit


----------



## Noitoen (Dec 27, 2009)

One thing I've noticed is that it switches itself off although it still keeps track of movement. It uses a 3volt lithium battery which I'll replace with a couple of alcaline AA's or AAA that will last longer


----------



## Twmaster (Jan 2, 2010)

Why not power it with a 3V wall wart?


----------



## Noitoen (Jan 2, 2010)

When the first battery goes I'll decide. My cheap Chinese calliper went through the 2 supplied batteries in a jiffy. Bought a pack of 6 in a "dollar" store and those were worse. Finally bought a "brand" battery and it's holding for more than 10 months so I figure that those batteries come almost empty and are not worth the packaging they come in


----------



## Twmaster (Jan 2, 2010)

There are different chemistry versions of that battery. Common are alkaline and silver oxide. The SO batts last longest.

I have three chinese calipers. One dirt cheap one made of plastic and two stainless steel ones. The older of the two stainless has lasted me for months thus far on the original battery, the plastic caliper killed the battery in three weeks or so.....


----------



## Blogwitch (Jan 3, 2010)

I would just like to add that sometimes it isn't as simple as plugging a wall wart into the scale.

Somewhere on the site, this was discussed in detail by Sandy and John S, and it ended up that John S made me a control box to get the electrickery bits right. It is something to do with the battery, and the effect of putting wall wart power to it. I think it is liable to explode or something else nasty. I would suggest you try to find the post.

This is how mine is fitted







And I also have a remote readout to it that is stuck on top of the normal DRO display.







One thing that should be done is replace the battery with a cap, otherwise you can get all sorts of spurious readings as it picks up pulses along the power feed cable, mainly coming from the motor. It took me a little experimentation to find the correct value, but now it is rock solid. I have to leave it a little while if the unit has been switched off for it to recharge itself, but a minute or so later, it is good to go.






The scale and display is run from a small regulated wall wart.


Blogs


----------



## miker (Jan 3, 2010)

Blogs, what value Capacitor did you settle on?


----------



## Noitoen (Jan 4, 2010)

Usually a 100nF (0,1uF) ceramic or polyester is a god decoupling value.


----------



## Blogwitch (Jan 4, 2010)

Miker,

I tried a 0.1 uF as a start, and it just wasn't quite there, I was still getting interferance. Maybe it has something to do with the size of motor on the machine and cable run lengths.

0.22uF turned out to be perfect for my setup, and I have had no problems at all since. Except for the delay on switch on after it hasn't been used for a while, but as I said, a minute or so is really no time to be held up.


Blogs


----------



## miker (Jan 4, 2010)

Thanks for the replies. :bow: 

I have the same scale to fit to my new RF 45 clone and will want to eliminate the battery also.


----------



## Blogwitch (Jan 4, 2010)

Just to go off topic a bit. The sleeving I used for the cap legs is silicone tubing, designed for pole fishing (big in europe). 
It is made down to really small sizes, and if ever you make a really tiny engine, by using very fine syringe tube as the inlet stub, this stuff can be used as the feed tube.

O.5mm (0.020") diameter

http://www.fostersofbirmingham.co.uk/KS05G


Blogs


----------

