Triggering an IR receiver from a white object/paint

Discussion in 'The Projects Forum' started by avz10, May 30, 2009.

  1. avz10

    Thread Starter Member

    Apr 17, 2009
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    I have started to build a system/circuit to capture old cine 8/super 8 using the Cinecap programme.

    I am having trouble to get the IR receiver being triggered when a white blade moves passed the IR receiver.

    (There are three blades of which I have painted one white i.e. 2 black blades will pass before the white blade is supposedly required to trigger the system)

    For the system I used the following-
    A cine projector that can run as slow as 3 frames per second (Eumig 610D).

    The moment that the frame "stops" for a split second, you need your camcorder to record the image and these frames are put together by the Cinecap into an AVI file. So when the frame stops, a trigger needs to be activated. In this case an IR receiver is the trigger.
    (I also tried with a microswitch, but the capturing was erratic)

    My video camera is a 3CCD Panasonic NV GS250

    I have done the following: I converted a mouse (acknowledge James Rueben):

    [​IMG]

    Used the following circuit (acknowledge James Rueben)::

    [​IMG]

    Connected to an IR receiver:
    OPB608A
    [​IMG]

    http://www.datasheetcatalog.org/datasheets2/22/229105_1.pdf

    The IR receiver and all my connections (converted mouse; circuit board) are working well.

    My finger, or any white paper triggers a signal which captures a frame via my camcorder on Cinecap, BUT, the paper, my finger, etc need to be very close to the surface of the IR receiver to trigger the signal.

    As mentioned before, I painted one of the three blades white, which will hopefully be triggered by the white blade going past.(acknowledge James Rueben):

    [​IMG]


    It only works when I bring the IR receiver very close to the stationary blade.

    If the blade rotates at 3fps, it does not trigger a signal, although I bring the receiver quite close.


    What is the solution?:

    I can see two possibilities
    1. Either put something on the blade ? white paper, other material which the IR receiver will pick up (this is where I need advice and this will be the easiest),
    2. Or get a stronger?? IR receiver.

    I feel that there must be a way to produce a strong input by means of some material to create the trigger. I used PVA paint.

    Any advice will be helpful. Will try it out in the next week or two.

    Regards
    Albie

    I need to acknowledge the help I got from James Rueben in this regard- he initiated the project, with the initial input from Ronypony.
    Having Trouble with DIY Telecine (8mm) System - VideoHelp.com
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    What do yo mean by very close? The OPB608 A/B/C are designed for working distancees of 0.05 to 0.375".

    John
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    I think the film is opaque to IR. You might try an optointerrupter to look at the sprocket holes. There will be a fixed number of holes between frames.
     
  4. avz10

    Thread Starter Member

    Apr 17, 2009
    20
    0
    Distance is very close ± 1-2mm, before the switch is triggered. So if I wave a white piece of paper 1cm in front of the detector, it does not trigger it.

    This is how the set-up should be:

    Projector projects to a lens (the Eumig allows for speed to go down with a gear system to 3 fps), produce an ariel image which is captured at 3fps. This is not my set up.

    [​IMG]

    Initially tried a microswitch, but this works erratic, especially at the start of film

    [​IMG]

    Cinecap program- screenshot

    [​IMG]

    The photo that I have posted of the IR receiver next to the blade, is not mine. I havent fixed mine, but this is how I painted a blade.

    Someone advises that in stead of paint, I use a thin mirror or foil on the blade. Any comments on that?
     
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    1 cm = 0.394"
    2mm = 0.079"

    It sounds like the optical reflector unit may be operating within its specifications. They do sell a "V" version that is supposed to work up to 1.5" (3.8 cm).

    Those reflective units are made for close monitoring. If you want longer distance, there are other units, you can make your own, or use a photointerrupter, as suggested above.

    John
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    What IR diode current are you using? Might try upping current to 1/2 A @ 10% duty cycle with one+- kHz cycle rate. Integrate received signal to give a single pulse per revolution.
     
  7. avz10

    Thread Starter Member

    Apr 17, 2009
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    Well, I have some feedback as well.

    Please consider the following suggestions:

    1. As said before, change the colour of the blade to "foil" or alumnium paint.

    2. Increase the value of R2 to 33k up to a 100k

    3. Shine a LED light or an IR light on the blade.

    4. Or use a stronger IR detector as John said

    Otherwise, use a Photo interrupter. Sounds good, but that practice might be harder. One will need to extend one blade out of three to go through the interrupter. This mighgt be the tricky part. One will nee to "lengthen" the one blade and make sure that part goes through, what I believe, is a 3mm gap.

    Thanks for the comments

    Albie
     
  8. avz10

    Thread Starter Member

    Apr 17, 2009
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    Sorry Bernard, I'm too much of a newbie to answer the questions!! Tell me where to look

    Albie
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Consider the datasheet:
    [​IMG]

    The device you have is designed for sensing at close range, such as detecting paper feed in a copier. The datasheet makes a point about the sharp roll off in sensitivity with distance. It uses a laser IR diode, and the datasheet mentions a special plastic housing for absorption of stray light. You might get a slight improvement using a coating that is more reflective of IR than your white paint. As for shining other background IR, I don't see that that would help more than hurt by causing false triggers. What you appear to have is a square peg and a round hole situation. Why force it to go a greater distance?

    A version of that sensor that works at greater distance is made. You should also consider one of the typical modulated emitters and detectors (see: Vishay). They get great range and very few false detections.

    Finally, an interrupter-based design seems like it might be the easiest, or simply tighten up on your design tolerance. A clearance of 1/16" is huge in mechanical design.

    John
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    For your IR diode ,are you using 5V with 180Ω? If so change 180 to 68 or 75Ω 1/2 W. I pulled a reflective sensor out of junk box ,fed diode with 20mA, used Ω meter to measure collector to emitter resistance. On X 10k scale easily detected hand or white paper at 10cm, but stray light would be a problem, on X 100 scale, background light no problem good detection at 2 cm, white, silver , any thing[almost] except dark colers.
     
  11. avz10

    Thread Starter Member

    Apr 17, 2009
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    Well Bernard, this sounds like an easy first option to reduce R1 to 68 or 72 and see what happens. If that doesn't work, try the foil etc.

    Would you change R2 to 100k as suggested?

    Hopefully this will work, if not, I will consider the OPB608V as shown in the graph or a photo interrupter (will need to extend the white blade) or else something like the modulated emitters and detectors.
     
  12. avz10

    Thread Starter Member

    Apr 17, 2009
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    I'm still not home, but in the mean time looking at all the options.

    My first step will be to change my resistors and try some foil on the blade.

    If that doesn't work, I think I will go the photo interrupter route. Please look at this site, as they are close to me. If possible, give me an opinion of my options. (If I go this route, I thought of glueing a small piece of rigid plasic on one of the 3 blades. That will then break the circuit. Comments??)
    http://za.rs-online.com/web/search/...ount=47&Ne=4294958012&N=4294781996+4294955625


    Regards
    Albie
     
  13. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Change R1 to 100 Ohm. A value of 68 Ohm will take ia above it's max. operating specs(!), which you shouldn't even go near. A value of 100 Ohm => 35 mA, which is a safe value according to the datasheet).

    Then change R2 to 100 kOhm and you should be in business. You might wanna fine tune the value, so a 10 kOhm resistor in series with a 220 kOhm (or 470 kOhm) trimmer could be used instead.
     
  14. avz10

    Thread Starter Member

    Apr 17, 2009
    20
    0
  15. bertus

    Administrator

    Apr 5, 2008
    15,638
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    Hello,

    I would take a sharp look at the slot width and slot depth.
    These values determine the size of the flag that can pass though the interupter.
    And the way of mounting it.

    Greetings,
    Bertus
     
  16. avz10

    Thread Starter Member

    Apr 17, 2009
    20
    0
    I'm not going to have time today to buy resistors, but this what I'm gonna do, as said before:
    Buy the resistors and a photo interrupter (2 US dollar) at the same time. Will try the resistors, but if I struggle, will try to install the interrupter.

    [​IMG]

    [​IMG]

    [​IMG]

    From the side:

    [​IMG]

    [​IMG]

    This is basically the available space. I think if I glue rigid plastic to a blade, it will work quite well. Thought of an old X-ray and paint it black.


    Please help me to choose one or two photo interrupters from this site, as this is where I can buy. This should be compatible with my original circuit.
    :
    http://za.rs-online.com/web/search/...ount=47&Ne=4294958012&N=4294781996+4294955625
     
  17. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Ouch, $ hurt, try The Electronic Goldmine, infrared items.
     
  18. avz10

    Thread Starter Member

    Apr 17, 2009
    20
    0
    No, its not that bad. I'm in south Africa, so the prices are divided by ten- most of the items are between 2 and 3 USD!
     
  19. avz10

    Thread Starter Member

    Apr 17, 2009
    20
    0
    I need serious help. This is my set-up so far:
    [​IMG]

    [​IMG]

    On request, I tested values at different points, using the original configuration (R1 180 Ohm; R2 6k8 Ohm)

    Here are the results:

    With the IR detector facing away from the blade:

    A: 1.3V
    B: 3.4 V
    C: 3.4 V
    D: 4.25 V

    With the IR detector facing towards the stationary blade:

    A: 1.3V
    B: 1.55 mV
    C: 3.4 V
    D: 4.25 V

    .


    E: 4.25
    F: 3.4
    G: 3.4

    E: 4.25V
    F: 3.4V
    G: 155mV

    0.02mV

    So it looks as my point E just produces 4.25V.

    With R2 replaced by 100k Ohm

    B (Output) Stationary: 3.1V (facing away from white blade)
    Facing white blade: 0.07 mV
    Moving: 2.4Volt
    Does not trigger “Capture” on Cinecap

    With R2 replaced by 100kOhm and R1 replaced by 68 Ohm:

    B: Stationary: 3.38V (facing away from white blade)
    Facing white blade: 0.37 mV
    Moving: 1.68Volt
    Does not trigger “Capture” on Cinecap

    So, I am not sure what I am doing wrong.

    I bought this Slotted IR optical switch yesterday (OPB365T), just in case I get stuck: Datasheet:
    http://www.digchip.com/datasheets/parts/datasheet/344/OPB365P55.php

    [​IMG]

    Does the beam need to be broken in that first 1mm transparent part, or does the object need to go deeper in the slit?

    [​IMG]

    If so, I can try to mount it close to two movable parts, that move only when a frame advances (so it is stationary and then either move down- that white piece)
    [​IMG]

    Or to the right:
    [​IMG]

    These two possible trigger points are very consistent.

    So, should I try this optical switch, I need to know the following
    1. How deep should the object need to go in the slit (because if it needs to go deeper, it might be difficult)II thought of attaching a rigid plastic to the "moving" side of one ot the trigger points.
    2. What wires should be connected to what pins (For me this is very important, being a newbie to electronics)
    3. Do I need resistors?

    Thanks
    Albie
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    This is what I see from data sheet. Optical slot is .05 in wide, so should be able to resolve 2mm linnes with 2mm spacing. Vane should completely cover IR window or dip into slot about .2 in. Nice pictures.
     
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