Touch Probe

[EdK]

(11-16-2013, 01:36 AM)Mayhem Wrote: I read that as saying the transistor option will come later and the schematic posted was the fixed version of the original.

...

Yup, after rereading it I see that now. My bad.

Ed

[claudef]

I finished machining the last parts of the probe today. I pressed the ball in their cavity with a drop of Locktite 609, after cleaning them with spray degreaser. It looks like this will work fine. Some of the wiring is done in preparation for the final circuit which should be ready by the weekend. It looks like the final wiring will be a pain, the LED is installed into the ball ring and sticking out .200”, there is a pocket in the bottom cover plate to house the protruding LED, this should illuminate quite well.

[awemawson]

When I made an 'electronic centre finder' (not really electronic, just LEDs and batteries) I pushed the LEDs out from inside through radial holes so just a bit protruded, fixed them with Loctite, then machined them flush - made it look very professional (I also alternated red and green leds round the circle, but that was just being flashy! )

Andrew

[Mayhem]

(11-20-2013, 03:47 AM)awemawson Wrote: ...but that was just being flashy!..

No pun intended right?

Do you have any pics of this?

[awemawson]

Photos as requested !

Must be at least 12 years since I made that

Andrew

[claudef]

'awemawson'
Your probe looks good, how many batteries did you use and what type.. how long do they last. Is your power source internal to the probe body or external.
My first test with LED's drained 2 LR44 batteries in a few hours.
I like the body diameter of your probe, I was hoping for 1" Dia. but had to go for a little under 2" to accomodate the electronics.
Do you still have the plans, are you using the balls and pins method also?
Thanks for the feedback, Claude

[awemawson]

Claude,

This is a different animal to yours - it is only a touch sensor for finding the edge of a part. The probe 'ball' has a retaining spring pulling it upwards into the tubular lower shaft. This shaft is insulated by being mounted on a piece of paxolin. The ball spring is in series with the leds which are in series with the batteries and a resistor. When the ball contacts the workpiece the circuit is completed through the machine hence the leds light up - in the picture I've just crept up on the vice fixed jaw.

If I remember correctly there are three button cells of the lesser diameter than LR44 in a plastic tube - I wanted to keep the shaft diameter down to 1/2" so it could go into a normal chuck for setting up rather than have to mount a 20mm collet as per a commercial one that I have.

I believe I have only changed the batteries ONCE in the life of this beast, which as I said earlier is best part of twelve years.

Plans: good heavens there were no plans ! I made it up as I went along.

Andrew

[awemawson]

OK I've opened it up. There are four '377' silver oxide batteries in the mounting shaft. I've included a picture of the commercial probe I mentioned that has a 20mm mount. The one I made is 1/2".

This has prompted me to order new batteries for the one I made !!!


Andrew

[TomG]

I've been looking into these things a bit and found a source for styli. They have all different shapes, sizes and materials, but a small ruby ball with a stainless shaft is about $35, a carbide shaft adds another $10 or you can sell the cow and get a ceramic shaft for ultimate stiffness for another $100. The stainless or carbide version seems adequate for general purpose work and seem like a better option for the styli than making your own.

Tom

[claudef]

TomG, thanks for the info, yes I did look at the rubie probes but decided to make my own using a dial test indicator tip. It has a 2MM ball on the end so 1MM from center is easy. The spring I am using on the probe is fairly light in tension so deflection should not be a problem, specially on my machine.
The circuit is completed and tested, it consumes 20mA with LED lit and 0.002 mA in standby mode, this converts to 9 hours with LED lit and 90000 hours in standby.
I should get the circuit on the weekend so next week I solder it in and function test.
Claude