Inscrutable Chinese Edge Finder

[dkaustin]

I picked up a cheap LED edge finder (see image), thinking I would wire it up to the accessory port on the Tormach. Now that I have it hand, though, darned if I can see how to open it up. Anyone have any ideas?

[Bubba]

If yours is like the one I have, the knurled end un-screws to reveal the battery compartment! You will then need to make up some wires to tie it in. There used to be a "how to" on the Industrial Hobbies site on how to do it.

[dkaustin]

Before someone suggests it, yes I do know to take off the battery cap on the end. That opens up the battery compartment, but does not expose the guts. The works were undoubtedly inserted from the open end, but how they are secured is a mystery (epoxy, isocyanurate, ?).

It was probably never intended to be disassembled, but why should that stop me?

[Bubba]

On mine, they were just stuffed in there! No epoxy, no glue etc.
I forget how I got it all out, but it wasn't hard.

Also, since the last note, I found my copy of the IH stuff if you need it.

[David Bord]

Originally Posted by Bubba On mine, they were just stuffed in there! No epoxy, no glue etc. I forget how I got it all out, but it wasn't hard. Also, since the last note, I found my copy of the IH stuff if you need it.

Bubba,

Would you mind sending me a copy of the IH doc to djborden (@) gmail.com

Do you remember where you bought your edge finder?

David

[Bubba]

David,
You should shortly receive a couple of pdf's in a zip file with the information.
As for my probe, I think I got it from Enco when it was on sale a couple or four years ago!

[dkaustin]

For anyone who's interested, I figured it out. You pull out the ball on the tip until you expose the hook eye on the end of the spring, then detach the ball from the spring. The guts then slide right out thru the battery compartment.

Once I was over that hurdle, it was relatively straightforward to wire it up the Tormach using a 4N35 optoisolator.

Best part is, it works! Much quicker and easier than using the wiggler-type edge finder.

[David Bord]

Thanks!

Can you tell me if the tip will go off center once it touches and then pop back? Meaning, is there there some over run in the tip to prevent it from beaking?

Also, do you find that it was fairly accurate being centered on the spindle?

Again, thanks for the assistance!

David

[saabaero]

I'm curious to know what your accuracy and repeatability is with this probe.

I have a number of different types of electrical continuity probes like these and never had very good results with them. It seemed like the steel to steel electrical conduction wasn't that good. A little contamination on the surface, a speck of dust or slight corrosion gave me inconsistent results. When I tried to use them with the spindle rotating the results were even worse.

[dkaustin]

David--

The tip on mine will pop over if you press it, but that just seems to be protection from overtravel. In use, the Tormach control software responds at the first contact, and the ball doesn't move at all. It's still early days, but so far this probe appears to be accurate and repeatable.

By the way, I ordered my digital edge finder from 800watt on ebay (Yeah, I know his reputation, but I just held my breath and took a chance. Had no problems at all). The finder has a 3/4" shank, so it's big enough to hold the required electronics and fits the Tormach TTS collet.

[David Bord]

Originally Posted by dkaustin David-- The tip on mine will pop over if you press it, but that just seems to be protection from overtravel. In use, the Tormach control software responds at the first contact, and the ball doesn't move at all. It's still early days, but so far this probe appears to be accurate and repeatable. By the way, I ordered my digital edge finder from 800watt on ebay (Yeah, I know his reputation, but I just held my breath and took a chance. Had no problems at all). The finder has a 3/4" shank, so it's big enough to hold the required electronics and fits the Tormach TTS collet.

great, thanks! I just ordered one from him. Did you wire based on the IH instructions? If not, any tips? Did you have any problems getting the guts out?

David

[dkaustin]

David--

The IH notes were a starting point, but I still had to work out the details. See the attachment for a schematic.

Once I detached the ball from the tip, the guts just slid out thru the battery compartment. Just pull the ball out far enough to expose the eye hook on the end of the spring, then unhook it.

If you don't already have it, you can get a MIDI cable with 5-pin DIN connectors from Radio Shack or any number of sellers online.

I soldered the optoisolator, resistors, and the LED from the edge finder to a small piece of perf board that fit inside the battery compartment. Make sure none of the leads or wires contact the inside of the casing.

The casing of the edge finder is hardened. I used a carbide endmill to make the hole for the cable.

It's fiddly work getting everything into the casing. It took me more than one try, but I'm happy with the final result.

Good luck!