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Author Topic: Index  (Read 842 times)

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Offline MN300

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Re: Index
« Reply #20 on: March 14, 2020, 10:59:52 AM »
0.71V is right for when light is reflected by the target but 1.26V indicates too much light is is received during the off period.

The best solution is to increase the light to dark ratio. Here are some things to try.

Shield the sensor from room light. Does the 1.26V reading change?

Make what the sensor sees when the target is not in view less reflective. Try changing the angle to reduce specular reflection. See attached PDF

Increase the reflectivity of the target. Retro-reflective tape is much better than white paint.

https://multimedia.3m.com/mws/media/295767O/reflectivity-flyer.pdf

If an optical solution cannot be found you can experiment with increasing the emitter resistor. Determine the resistance for two points, when the high value approaches 5V and when the low value starts to rise.
Assuming that with time dirt will reduce the light, you should select the lowest resistance that give full output.
The difference between the two points gives an indication how much dirt the system will tolerate before the lower voltage rises.


Re: Index
« Reply #21 on: March 14, 2020, 12:29:02 PM »
YES! Turned off the light and I got 4.7v (no reflekt) and .71v (reflekt).
No I am going to mont it to my mill. It will be enclosed so no or little light vill be around.
Let you know how I am getting on.
For now, thanks again a lott. Without yours help I wouldn't have managed!
Re: Index
« Reply #22 on: March 16, 2020, 07:33:43 AM »
Hi.
I need some more help.
When I test the sensor with a Travel Adapter giving 5.0v and 1.0amp it works fine, but when wired up to the mill it will not work at all. I measured the built in power supply at the mill to 4.88v. I think that is the reason. Can anything be done?  Reducing the 150 ohm resistor to 100 ohm?
Or is the only solution to use a separate external supply?

Offline MN300

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Re: Index
« Reply #23 on: March 16, 2020, 08:30:38 AM »
The difference between 5.0V and 4.88V is small. The device should still work. What are the voltages you read when you rotate the shaft?

Check your wiring, is there a bad connection?

Is changing the power supply the only change you made? If you connected the output to the mill try disconnecting it when testing.

I can made better suggestions when I read what the voltages are.
Re: Index
« Reply #24 on: March 16, 2020, 09:08:20 AM »
I have checked the voltage of the external supply to be 5.12v (not 5v).
The device is not mounted on the mill, but is wired up to the mills supply.
I get the following readings across earth and signal: flickers between 1.4 and 1.9v. There is no differences if reflectit or not.

Is changing the power supply the only change you made? yes

Offline MN300

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Re: Index
« Reply #25 on: March 16, 2020, 09:38:38 AM »
I am trying to think of a combination of events to explain what you see.
If the emitter is not working then room light could explain the flickering output. If this is the case then shielding the sensor will increase the output voltage.

As I mentioned before the output of the emitter can be checked with a digital camera. To test your camera you can point your TV remote control at the camera and push a button. You will see a flickering light. Once you see this work you can move on to checking the emitter.

The voltage from earth to the junction of the emitter and the resistor should be 1.7V.
Re: Index
« Reply #26 on: March 16, 2020, 10:27:50 AM »
Yes, the emitter do work, checked with my camara.
I measured the voltage as you mentioned to flicker between .4 and .9 v. I tried to shelter the sensor with little effect, not notesible.
To bee sure I measured the right place I attach a drawing showing where I did the measure.
Sorry, sent you a wrong dravig. Here is the right one
« Last Edit: March 16, 2020, 10:35:47 AM by sivtek »

Offline MN300

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Re: Index
« Reply #27 on: March 16, 2020, 10:43:22 AM »
The reading of 4. to .9V at the emitter pin 3 does not make sense. If the emitter is working the voltage there should be well over 1 V.

Let's try going back to the setup that once worked. Can you try the power supply you called the Travel Adapter again?
Re: Index
« Reply #28 on: March 16, 2020, 11:14:42 AM »
No it do not work any more. It did work this morning, but not now.
The emitter is working and the voltage at pin 3 was 1.3v and the supply round .8v.
BTW. in the drawing  the R1 is shown as 100 ohm, but 150 ohm is actually used.

Offline MN300

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Re: Index
« Reply #29 on: March 16, 2020, 11:38:57 AM »
Since this worked at one time something has changed. Either there is a wiring fault or the sensor has been damaged.