spindle index, encoder, home/limit switch

[Wm McNett]

I have a few questions/comments about this circuit.
http://www.dakeng.com/spindle_ckt.jpg
LM339 is a Quad circuit and only one circuit is used?
14-Dip comparator (differential/offset)
why not use one of those single circuit TO-5 little metal cans or even an dual circuit 8-Dip (LM393)
would not a high seed one be better?

7404 has 6 circuits and only one circuit is used?
What is it?
Gate?
PIC?
cnc4pc.com's Index Pulse Card uses a HD74LS04 which has 6 circuits and only uses one circuit

http://www.wrathall.com/Interests/CN...le_encoder.htm
http://www.wrathall.com/Interests/CN...der_layout.pdf

This looks much simpler;
http://groupyahoo.com/group/turbocnc...ndexSensor.zip schematic.jpg

This look better yet, it's all ready built
http://www.wrathall.com/Interests/CN...ion/GP1A05.pdf

The local Radio Shack don't have most of these pieces.
The have the infrared diode/emitter, don't have the detector.

So I'm looking at buying the pieces from Digi-Key, Jameco, Mouser, Newark InOne, ...... and replacing the LED and detector with a slotted unit.
Something like cnc4pc.com's Index Pulse Card (ECG3100) OR ajaxcnc.com's Z-axis Optical Limit Switch
Then again with a reflective flag and a reflective sensor I could make something like industrialhobbies.com's optical limit switch.

Are usec. and nsec. the same or is ns much faster than us?

Wile searching the net I found a circuit that uses a LM358. One electrician said it would be faster than the LM339 but it would cost more. The 358 is an amp not a comparator.

Also, I've found out that this will also work as a switch.

Wouldn't this do the same thing?
http://robotics.me.jhu.edu/~llw/cour.../lab_02_09.pdf
or this
http://www.electronics-lab.com/projects/misc/017/

I guess I'll just have to buy some pieces and run a few tests.

Bill

[Al_The_Man]

1nsec = 1000µsec
If you just need to use the slotted switch detector, I don't know why you would need a comparator?
What do you need super high speed for?
Al.

[Wm McNett]

why is the comparator used in the circuit if it's not needed?

[Wm McNett]

according to this;
http://www.ee.washington.edu/circuit...CIISCHEMIR_007
all that is needed is the slotted opto switch and two resistors.

[Al_The_Man]

Thats what I would have thought.
Al.

[Wm McNett]

if I'm reading this correctly; the comparator is in there for "noise immunity" OR "faster switching speeds"
OPTEK's Application Circuits for the Phototransistor Switch
http://www.optekinc.com/pdf/App%20Note%20213.pdf

Bill

[Al_The_Man]

The comparator essentially selects a level at which the turn on point is detected, If for instance you wanted to select turn on at a detected level of light, or sensitivity.
Most operations use the either on or off due to the differences in characteristics in opto isolators.
I have found they are not very good at linear amplification, unless you use something like the H11F1 which has a linear resisitive output.
Al.

[ViperTX]

Look at the outputs with and without the comparator and you'll see the difference....the comparator squares up the signal.....conditions it....

[Al_The_Man]

For squaring, I would tend to use a schmitt trigger, the comparator is usefull if you want to set a certain threshold level.
Al.

[Wm McNett]

That's what I was seeing, makes it ON or OFF not somewhere in-between.
I should take a class at the local Vo-Tech.
7404 is a NOT gate
http://www.kpsec.freeuk.com/gates.htm
"A NOT gate is also called an inverter."
http://www.boondog.com/tutorials/irled/ir.html
"The 74LS14 is a Schmitt triggered hex inverter."
I've also found out that a comparator is one of the many applications of an Operational Amplifier (op-amp).
http://encyclopedia.lockergnome.com/...onal_amplifier
I just snagged 100 Optek OPB875P55 switches off eBay for $6.25, that will give me a few to play with.

Bill

[Wm McNett]

I finally cut my first cnc chips last Saturday.
Now I must get my spindle index circuit together with what I have.
So, with my LM358 Op Amp and another resistor I'll have my Schmitt trigger.
http://www.radio-electronics.com/inf...tt_trigger.php
http://hyperphysics.phy-astr.gsu.edu...c/schmitt.html
http://www.swarthmore.edu/NatSci/ech...b2(OpAmp).html
http://webpages.ursinus.edu/lriley/r...its/node5.html