Homemade DRO...maybe...sort of...

[zeeprogrammer]

Brought a scope home for the weekend...here's a shot of what the clock and data lines look like from the caliper. A bit noisy but filterable. I'll add a capacitor anyway.

The first burst of 24 clocks is the position relative to zero (that you set). The second burst is the position relative to an absolute zero that gets set when the caliper powers up.

Trapped at home!!! Here's a shot of today's snow...

 

[zeeprogrammer]

Got the tach hooked up over the weekend and could see the change in signal on the scope when I changed lathe speed. But I don't have the timer right so the display isn't showing the correct speed.

Unfortunately, I'm going to have to set this little project aside for a while. Pressure at work has increased to the point that doing more embedded programming when I get home is the last thing I want to do. Struggling to get workshop time as it is...and my judgment is suffering.

Can't wait for the trials to be over. In June!!!

It'd be different if the job were eating pizza (I can eat that for every meal of every day)...or curry!!! Curry!!! Oh man I love curry...you guys in the UK have it great!

See what I mean about judgment?

 

[Deanofid]

Ya had me at pizza.

 

[zeeprogrammer]

Last post here was Feb 10.

Finally got my package of parts yesterday...ordered in February.

Includes connectors, capacitors, caps for the buttons...and the more important bridge rectifiers and transistors for the lathe/mill (which I didn't need as it turned out).

Order was delayed cause I stupidly said to wait until all parts were available. Was waiting for the caps for the buttons.

Then delayed again because, in the meantime, a fraud alert was put on the credit card and the card canceled. Had to give them the new information.

"Does this mean I'm back on the DRO?" you ask?

No. Work is such that doing any programming when I get home is the last thing I want to do.

"Then why the post?" you ask?

To remind myself it's still hanging around....that or to move it up a page.

Yeah yeah. You all already know I can be rank about that. :big:

 

[4156df]

Zee,
I had forgotten about this thread. Nearly crapped when I scrolled and saw the snow photo. Then I realized that was in Feb, not today.
Dennis

 

[T70MkIII]

Zee - I'll bring this up a page or two.

I assume you are going to power the calipers from the Shumatech board. Are you going to put a capacitor across the caliper battery terminals? If so, what value are you going to use? I've seen 4.7uF up to 100uF mentioned elsewhere but no rationale given for the particular choice. I was wondering if you've calculated something more specific.

Without knowing any electronic theory I would have thought the higher value would filter better, up to a limit.

 

[zeeprogrammer]

I had forgotten about this thread.

I was trying to.

I assume you are going to power the calipers from the Shumatech board. Are you going to put a capacitor across the caliper battery terminals? If so, what value are you going to use? I've seen 4.7uF up to 100uF mentioned elsewhere but no rationale given for the particular choice. I was wondering if you've calculated something more specific.

Hi 70MkIII. I have to admit I'm not sure I'm going to take this any further. If you've been reading the thread...it involves a little too much of the kind of stuff I do for a living. And therefore not real relaxing. ;D Some other people (Trout for one) have come up with DROs that I think are more to my liking. A bit more money maybe...but simpler to install and use. I don't need the fancy stuff the Shumatech provides. I just want to see a display of my position.

But to answer your question...I haven't done any calculations at all. I was going by what Shumatech and other have used. If I recall correctly, the higher value is better. 100uF sounds right but I haven't checked.

Darn. You made me read the thread some. It talks about my stuff at work going to trial in June. Nope. Now it's September. It's a long summer.

Thanks for looking in.

 

[T70MkIII]

Thanks, Zee - I asked because I have a 350 winging its way towards me, so I've been re-reading all the threads I can find. If I hadn't picked it up so cheaply on eBay (I don't need the other functionality either, but this is a pre-built PCB) I would have probably gone the other way myself - so to speak. I'll whip up some cables, grab some cheap calipers and give it a whirl.

Best of luck with the other DRO solution. It looks like a good one too.

 

[johnthomp]

Carl,

I went the route you are taking a few years ago on my previous mill.

Even though these digiverns are a cheapy variety, they do need to be treated with respect when it comes to chopping them about. Your problem might be on reassembly, and you haven't got the correct pressure on the phos bronze wiper strip that runs along the edge of the main scale bit. They can be a bit fiddly to get back into the correct position and adjusted up.

Over the years, I found this was the most common area for failure, especially when you were half way thru a job. You need to get that wiper adjusted so that it doesn't lock the unit up, but still allow a good clean contact. The other main area of failure is the carbon pick up strips on the back of the display itself, especially thru condensation, you will get spurious readouts on the display. That requires a rather delicate strip down job of the whole display unit and the tracks very carefully cleaned down with methylated spirits.

Using digiverns and read heads of this design is fine, but I found that were rather unreliable at the best of times, even when well protected. Eventually, after about 3 years, and having many spare heads to swap over at a couple of minutes notice, I gave up on them and went to glass scale versions. After spending copious amounts of money replacing the scales, it worked out cheaper and less frustrating in the long run to swap over.

Don't get me wrong, they are a relatively cheap method of getting a DRO system, and they do work accurately most of the time. But this type of scale, no matter what anyone tells you, is not designed to work in the environment you will be putting it into, especially if you use suds as well.
The only reason they manufacture the scales in all lengths is because people still think they can get a good working system from them, and the manufacturers will continue to produce anything if it makes them money, whether it is fit for purpose or not.

I do still use one of this type on the quill Z axis of my mill, but only because it is out of the way of all the nasties, plus I have done away with the battery problems (another thing that needs to be addressed) by running it on a small power supply that a friend very kindly made for me.

That is just the way it didn't really work for me, it just might be OK for yourself.

BTW, when mounting it onto the tailstock, you really need to get something on there to compensate for the twisting motion of the barrel. I would suggest a double ended ball joint available from most model shops.

Blogs

sorry for butting in here fellas but the dj world can help with cleaning the tiny carbon strips on digital readout components i used to be a dj and had at one point serious trouble with *** ash ruining my crossfaders switches and sliders and evry time they failed would be during a live performance i used to strip them down clean them up with meths and rebuild the mixer unit during live performances and who says us men cant multitask it was a well known party showoff trick i had doing all that but still playing a flawless 2 hour set
i later discovered an aerosol chemical for cleaning electronic switches wich became affectionaly known as crossfader in a can and i think its still available on
HTFR.com they mainly deal with evrything a dj could need but some things they supply have a multitude of tasks and capabilities for anything

 

[T70MkIII]

Thanks for the tip, John.