Optical limiting switches

[oxford]

I had searched through CNCZone for building some simple optical switches.
This thread was what started me off:

http://www.cnczone.com/forums/general_electronics_discussion/54074-optical_limit_x2.html#post422008

I liked IH's and Tpworks designs, but neither would not fit in my machine. I also needed to play around a little to get the electronics right.

I kept tabs on what I did in the hope it will make the process easier for others.

At the center are:

http://search.digikey.com/scripts/Dk...me=QVA11134-ND

I used a .5" thick plastic cutting board for housing. 1/8" x 1" Aluminum bar as a plunger and blade. Springs and epoxy from a local hardware store. Also, (gasp) resistors, wire, and PNP(packet of 15) transistors from Radioshack. Finally, shrink tubing from digikey I had laying around.

First used a table saw to cut 1" squares out of the cutting board. Used nine of the squares but made thirteen so I had some to play with. Also used saw to cut 1/4" x 1/8"x 1" blade/plungers from aluminum.

Used a drill press to drill out a pocket for the electronics with a 1/4" bit.

Drilled small holes for spring and plunger retainer clip. Cut springs to size and attached.

Checked alignment and cut with x-acto knife rectangles for plunging blade.

Put it all together with epoxy.

Disclaimer: I am not an electronic specialist and my design may kill your computer or controller. Try at your own risk:P

[Mr.Chips]

Nice job.

Could you show some more photos of the finished assembly, top and bottom so we can see the see more assembly details.

Does it activate when the sensor is blocked or unblocked?

Thanks

[oxford]

Thanks

The switches are unblocked when they are on/high.

For now, this is the last of the photos I have on hand.

[Mr.Chips]

Thanks

The switches are unblocked when they are on/high.

For now, this is the last of the photos I have on hand.

I see, the light sensing module goes up from the bottom.

Thanks for the explination and additional photo.

[Robin Hewitt]

Presumably the extra transistor is to counteract the hysteresis on the logic input reading it? Would you consider using a comparator next time?

I like opto slots for end detection because, unlike a switch, you can overshoot without destroying them

[oxford]

I had considered using a comparator.

However, I am more familiar with transistors and had a handful of them stashed in my parts drawer.

Size constraints were the last issue. There would be no way for me to cheaply get some surface mount chips that would fit during my vacation.

[Regnar]

I have been thinking about this for a few hours and want to know if you think this will work out. Pictures are below. Basically I was thinking of the same setup as the IH just with 1 switch and using aluminum or steel depending on what come out nicer. I still don't fully understand how the wiring is setup but I am going to try and have a guy at work help me out. Either way let me know what you think.

[oxford]

I like its shape and simplicity.

The one thing that is confusing for me is the pocket in the middle of the plunger.

It looks too far away from where the optical limiting switch is to trigger it.

The plunger movement when you include the size of the springs may inhibit the switch state from ever switching.

I would turn the middle pocket 90 degrees and have the photo-receptor triggered by the diode until the plunger moves away from its relaxed position.

[Regnar]

Good point on turning the middle pocket on the plunger 90 degress. I should have thought about that but I think I was just trying to give it as much strength. But your Ideal makes more sense especially if I use a 1/4 inch endmill.

I dont have the springs on hand so I had guess from the mcmasters catalog. Basically its a .5 dia. by .5 tall spring. I dont know if that was inside or outside dia nor do I know the thickness of the wire. I just drew it up guessing for proof of concept. I think as of now I am am going to do it in aluminum for the plunger and delrin for the housing. I still need to ad mounting holes and the cover holes but that will be added in tomorrow. Thanks I will post more pictures tomorrow.

I was wondering if you have the idiots guide for wiring these up? I can do just about anything mechanical but when it comes to electrical I am struggling.

[acondit]

My recollection is that you only need about a 0.035" hole for the emitter/detector pair and the center of the detector is located about 0.103" from the top edge of the optical switch (H22A1). So a 1/16" hole (0.0625") would be adequate and you could drill it 0.100" from the edge of your slide piece. Then your slide doesn't have to move very far to trigger.

Alan

[oxford]

The 1 pin is by the little dot on the optical switch.

This should help:

http://www.fairchildsemi.com/ds/QV/QVA11134.pdf

You can see the 1 pin reference if you look careful at the product photo here:

http://search.digikey.com/scripts/Dk...me=QVA11134-ND

The picture has the pins labeled in the wiring.

[Regnar]

This might seem like a dumb question but does "out" goto the breakout board or do you hook up the breakout board to the 5volt connection?