Re: [CAD_CAM_EDM_DRO] Home switch testing?

On Mon, 05 Jan 2004 05:45:47 -0000, you wrote:

>Hi, I just received some slotted opto sensors
>that I was planning on using for home sensors
>on my retrofit.
>This is where I got them from.
>
>http://www.allelectronics.com/cgi-bin/category.cgi?
>category=435&item=OSU-50&type=store
>
>They have 4 leads on the bottom two are for 6 volt
>power + and - and the other 2 are suppost to be
>a normaly closed switch wich is disrupted when a
>deflective object is penetrating the slot.

Well, probably not a switch.

>With my obvious limited knowledge about electronics
>I tryed to hook the sensor up to test its function
>using a couple of D cell batterys a 6 volt powersupply
>a small voltage lightbulb and a multytester for electronics.
>I have not been able to get this sensor to do any kind
>of verifyable disruption yet.
>I tested on 2 of the leads was continuety so I figured
>this must be the switch side.

well, that's the LED, probably.

>Testing to disrupt the lightbulb did not work in any of the
>various ways I tryed to set this up.
>Could any of the more electricly gifted persons please point
>out what I am doing wrong here.
>I suspect this may not work the way I think it would.
>The 2 sensing leads are suppost to be hooked up on 2 pins
>of the Parallel port of the PC, have not tryed this yet.
>How could I set this up for testing.
>

Let's give this a try.

1) the thing is infrared, so you won't be able to see it when it's on,
if you have a camcorder of some sort, or a digital camera, it might be
able to see infrared, otherwise, radio shack/tandy has a little strip
that will glow under infrared light, you can use that.

the emitter of light is an led. Wire a 470 ohm resistor in series
with it, and then ground one end, and run the end connected to the
positive end to the +5 volt supply, this will allow about 8 ma to flow
through the diode. When it's conducting, you can expect to see about
1.4 to 1.6 volts or so across the diode.

The second part of this is a photodetector. It's basically a
phototransistor. One end will be grounded. The other end (plus) will
go to the +5 volt supply through a 4.7 K ohm resistor. Take your
signal to the parallel port from the junction of the resistor and the
photodetector.

Electrically, this is the same as an optoisolator, probably of the LED
Phototransistor type. Look for specs on the 4N33 or 4N35 chip, then
that will give you some hookups to study. The difference here is that
you can put an object between the LED and the photodetector.

Measure the resistance and see if one port changes resistance with
infrared... you might be able to use a tv remote to try the sensor.

Harvey

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