Touch Probe

[claudef]

http://www.vinland.com/Touch-Probe.html
This web site shows the standard concept of the TP, the wire interfaces with the Digital Read Out (DRO) as the probe touches a part on the milling machine the DRO records the 3 Axis measurements of the position.
Now I’m not that sophisticated, I only want to pick up edges of parts or centers of holes and set my mill dials to zero.
I don’t want wires, I want it to be a self contained unit.
I will put two LED’s in the bottom plate, this material lights up quite nicely with LED’s.
I want the LED to light when the contact on balls is broken, not when the circut is closed.
This unit measures 2 “ in diameter and 2” high. I made the battery container and installed in the body (3 LR44’s) 4.5V. Now I need to make the cover for the batteries.
I have a friend working on the electronic to fit in this body.

[TomG]

I'm trying to figure out how this is supposed to work. It seems like it would take quite a bit of movement on the point to break contact on any of the balls.

Tom

[claudef]

TomG,
Any movement regardless how miniscule it is will break contact.

[DaveH]

This is interesting

DaveH

[stevec]

It sure is I'll be watching for progress reports Claude.

[TomG]

What are you going to use for a probe, a ball? If so, how will you center it on the axis of the shaft? Maybe a three point adjustment on the plate holding the balls?

Tom

[claudef]

Well, I was away all day today so the project stood still. Tomorrow I will make the battery cap then work on the probe.
TomG, yes you are correct, I will be using a ball and there will definatly be a 3 point centering feature. The design for the electronics is complete so I now know that it will fit into the cavity of the probe along with the spring, probe and ball ring. I will post pioctures as progress goes on.

[claudef]

Completed the battery cap today and also turned the probe. Tomorrow installing the pins and then the ball ring.
The design is completed for the integrated circuit, it measures 0.8 "long by 0.3" wide components R1, R2 and C1 will be placed under. It will give a thickness of about 0.3 "with 4 wires coming out.

[claudef]

This the schematic of the circut..

[EdK]

claudef,

There's something wrong with that drawing, or I'm misinterpreting it. Pins 4, 5, 9 and 10 are all inputs to NAND gates with nothing driving them so you have floating inputs with the NAND gate outputs driving the LED. Not a good thing. I think those four pins need to be connected to the other NAND gate inputs, pins 1, 2, 12 and 13.
The other thing using that particular IC is that the outputs will likely be fighting each other. It would be better to use an IC with open collector outputs. I would just use a transistor instead of an IC though.
Ed