Triggering an IR receiver from a white object/paint

Discussion in 'Electronics & Electrics' started by avz10, May 31, 2009.

  1. avz10

    avz10 Member

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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 fro Ronypony.
    Having Trouble with DIY Telecine (8mm) System - VideoHelp.com
     
  2. OP
    OP
    avz10

    avz10 Member

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    Just more detail I want to add:

    The 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? Or aluminium paint?
     
    Last edited: Jun 5, 2009
  3. Kindros

    Kindros Member

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    could it possibly be that it is not getting enough reflective light from the blades? Maybe a white led or even an ir led just shining in the blades general direction might help it?
     
  4. dakiller

    dakiller (Oscillating & Impeding)

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    If you can fit a photo interrupter in there, it'd work much better. You can find small ones in old ball mice
     
  5. Goth

    Goth Grumpy Member

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    What about one of these:

    http://www.jaycar.com.au/productView.asp?ID=ZD1901

    You'd need to fit it so that the edge of the blade fits in the slot in the device, and it will trigger on every blade, not just one. If you only want one trigger per revolution, you could maybe add an extra tiny little tab glued to one blade to trigger the photointerrupter, or use a digital counter to divide down the output frequency from it if it's triggered on every blade.
     
  6. OP
    OP
    avz10

    avz10 Member

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    Thanks for all the replies:

    I'm quite sure this is the case. Will definitely consider it with some other options (will first play with foil, get more lights on the blade- this will need to be 12 volt lights) and if that doesn't work might go the photointerrupter route

    Sounds good. If none of the others work, I will consider this one. (If I do this, then I will need advice with the wiring). But I do need every third blade to trigger the switch, so one will need to add something to one of the blades. Does it mean that everything that goes through the "hole" in the photo interrupter will block it?

    I just brought the modified mouse with me this week to play with and I am only at home on Saturday

    Albie
     
  7. merlin13

    merlin13 Member

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    Looking at that data sheet there's a couple of points I noticed:

    - the Test Condition diagram shows the reflective surface is parallel to the device. Is your fan blade?

    - the distance that device works at. The "Distance to Reflective Surface" graph shows the Collector current to drop off at a seperation distance of greater than 0.2 inches or 5 mm (also note the Test Diagram shows the spacing to be 0.11 inch from the stepped reference point, or .04 inch/ from the face of the device itself).

    If you want to keep using that particluar sensor it looks like you're going to have to look at:

    - shortening the distance from the device to the reflective surface

    - if it isn't already then making the reflective surface parallel to the device (mount the sensor at the edge of the fan blade, pointing in towards the axle, mebbe?)

    - boosting the output (as mentioned above, mebbe finding the right type of IR LED and fire that through the blades).

    - again as mentioned above, the word reflective makes me think sticking a small tab of aluminium foil or similar to the blade to increase the shiny, at least as a test.

    Just for a giggle, because it seems to work when stationary I'd also be inclined to check that the projector itself isn't generating buckets of noise on the wiring to/from the sensor and just blanketing the switching signal - got a CRO by any chance?


    Else just replace that sensor or the entire sensor setup with something a bit less picky - photointerupter as mentioned, that blade looks like steel so even a fast magnetic pickup sensor, etc.
     
  8. OP
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    avz10

    avz10 Member

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    Thanks for the advice. I'm not at home, but will start "playing" this weekend or next weekend.

    Just a few comments:

    -I was holding the sensor in my hand, so the chances are good that it was not parallel and the distances could have varied- but I got no trigger/signal while I was doing it.
    -I will definitely try the system with some reflection.

    What do you think of the advice I got from other forums:

    1. Increase R2 to 100k ohm
    2. Decrease R1 to 68 to 72 ohm?

    If everything fails, a photo interrupter sounds like a nice option. Will then need to extend one of the blades.

    Thanks
    Albie
     
  9. Davo1111

    Davo1111 Member

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  10. merlin13

    merlin13 Member

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    What you've already got seems to work when you get the sensor/blade separation down to what the datasheet reckons will work(and it does...), so it does feel like you've simply got a seperation/spacing issue.

    Personally I'd be a bit wary about driving the IR LED at full spec in a warm/hot install like that (the new R1 value that low), and depending exactly how the sensor handles the blade rotation boosting the output gain that hard may result in false triggering.

    But without fixing the separation you'll have to basically Give Her a Go and see what happens... :)
     
    Last edited: Jun 3, 2009
  11. aXis

    aXis Member

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    Maybe one of the following would help:

    1) Some sort of lens to help with dispersion.
    2) Some extra IR LED's ext to the detector, shining at the blades.
    3) A tube with an internal reflective surface to act as a light guide, bridging the gap between the detector and the blades
     
  12. OP
    OP
    avz10

    avz10 Member

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    Do you mean that if I shine an extra IR light on the blade, I will be able to increase the distance between the blade and the detector? Although there is space, it is difficult to fix an object in there.

    Merlin, would you firstly try to increase R2 or would you reduce R1 as a first option?

    I will try a bit with this, but it it sounds as if the photo interrupter is a very nice practical option for someone like me. Please look at this site and advise.
    http://za.rs-online.com/web/search/...ount=47&Ne=4294958012&N=4294781996+4294955625

    Regards
    Albie
     
  13. merlin13

    merlin13 Member

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    First option? I'd reduce the separation... ;)

    'Pologies for whipping the bereft equine but without having a fiddle (mechanically) I've got suspicions that you just ain't going to to get that particular sensor setup working reliably.

    Prove me wrong - change components.... :)

    There's just not enough info on the datasheet to show whether you'll get a serious increase in IR output at 50 mA, and being the annoying bastard that I am I still wouldn't drive the LED at full bore.

    Try an ohmies at say... 100 or 110 ohms, that'll work out to 32 to 35 mA though the LED and still leave some wriggle room - if it gets better but not completely then go Balls To The Wall and 50 mA (68 to 72 ohmies), if it doesn't then change tactics.

    Dumb Question - you haven't stuck a grubby finger on the end of that sensor, by any chance?...


    If you end up going New Tactic - how wide/thick are the blades, and how much pitch/twist/offset do they have?

    Photointerupter out of a mouse (there's squillions of dead mice around) should be easy to fit if the blades can slip 'tween the LED and sensor of those.

    And if those blades won't fit though then a short bit of dark stickey/Gaffer tape off the end of one of the blades damned well will. :D
     
    Last edited: Jun 4, 2009
  14. 2xCPU

    2xCPU Member

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    I'm interested to know why you think it's a problem.

    With R1 = 180Ω, The current (nominally) is limited to 18mA.
    But.... The spec sheet says the LED strobes at 300Hz and pulls 3A for 1uS.
    I'm not surprised it's not working reliably.

    avz10 Drop R1 to 68Ω - this will up the current to 50mA (I can see no reason not to).
    If the photo-transistor switches reliably with your finger etc. then R2 is fine and there is no point changing it.

    Do you know which of the OPB608's you have?


    Here is a better copy of the Data Sheet


    2.
     
  15. OP
    OP
    avz10

    avz10 Member

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    Some responses:

    Just remember English is my 2nd language- do you mean that the surface area can be dirty??

    I attach photos, probably 1 mm thick, but remember, only one in three needs to be triggered, that's why I thought to glue some plastic (like a piece of an X-ray to the end of one of the blades)
    [​IMG]

    [​IMG]

    [​IMG]

    If I go and by the resistors, I can just as well buy a photo interrupter.The prizes that I have seen are really cheap. Would save me another trip. So which of the following look like good possibilities?

    http://za.rs-online.com/web/search/...ount=47&Ne=4294958012&N=4294781996+4294955625

    I have the OPB608A

    Thanks
    Albie
     
    Last edited: Jun 5, 2009
  16. 2xCPU

    2xCPU Member

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    The data sheet I posted above says that the 'A' is ok up to 9.5mm, so it's mounting isn't too critical.

    You can see more clearly now, but the blades of the 'fan' have no pitch - it's not a cooling fan.

    2.
     
  17. merlin13

    merlin13 Member

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    Prefer not to drive components, etc at maximum Manufacturer's specs, unless I've got replacement spares handy that someone else is paying for...

    I'm curious as well - you're saying that piddly little sensor has to have a 3 amp supply on the IR LED to run properly?? :shock:

    I think you'll find the spec sheet is showing it can run it higher than 50mA - up to 3 amps providing you pulse it at max 1 microsec pulse width and the pulse repetition rate is no more than 300 times per second.

    Your newer data sheet does show some interesting info, though - the Reflective Response graphs show low values in comparison to printed ink for white plastic and silver tape.

    Wonder if his white paint isn't going to work terribly well overall, and even adding in a Shiny won't fix the problem either. Maybe if he wants to keep this sensor setup in place he'll have to go for a 890 nm IR LED fitted on the other side of the blades - waddya reckon?

    Else replace the OPB608A for a -V variant, the Distance vs Output curve shows it to be far friendlier on separation spacing.

    Or just scrap it and go for a photointerupter setup...
     
  18. 2xCPU

    2xCPU Member

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    Ah - that is Max spec too, but still, if it's almost working now, but too insensitive to be reliable, upping the brightness is the first place I'd start (100 Ohms is probably a good place to start).

    Reading the spec sheet, I'm unclear if it can be strobbed up to 300Hz or id does strobe at 300Hz.
    There is no maximum trigger freq. specified, but I would have thought it could manage a few kHz at least. In which case, strobbing the LED at 300Hz would produce the same in the output (when detecting). I can see some advantages to this behaviour, but it's only the A, B and C versions (not V and R) that include this behaviour, hence why I assumed it was 'normal'.

    3A for 1μs at 300Hz - averages about 1.5W - doesn't sound right to me.
    There is more info on the LED in the Data Sheet below - the OP240 is the LED in the OPB608.
    The App Notes also have some useful things to say too. (including: If optical signal levels are very low, increase the load resistance R2.)

    2.

    OP240
    Application Notes
     
  19. OP
    OP
    avz10

    avz10 Member

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    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 at the same time. Will try the resistors, but if I struggle, will try to install the interrupter.

    Some new photos with measurements:

    [​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.

    Please help me to choose a photo interrupter from this site, as this is where I can buy:

    http://za.rs-online.com/web/search/...ount=47&Ne=4294958012&N=4294781996+4294955625

    Thanks
    Albie
     
  20. merlin13

    merlin13 Member

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    Myeh, it's only a vanilla-flavoured IR proximity sensor. More than a bit odd that if it's already strobing/pulsing the LED internally off a steady DC supply you could then pulse the input power as well and still see (ha!) it work.

    You'd also be relying very heavily on the response curve of the phototransister if you pulse the LED input power with a single 1 microsecond wide hit - the data sheet reckons that's valid if you want to use it that way.... :)

    Proper data sheet would show whether the LED is internally strobing. Slack Manufacturer documentation, and we're now haggling with insufficient component data.

    However, your latest spec sheets shows the LED will boost its IR output by two-a-a-bit times if driven up to 50 mA - good find. That's what we would've been looking for here all along, gotta be of some significant help to drive it harder then the existing 20-ish mA.


    And I'm frowning at that 1.5 watt consumption/dissipation figure as well. Show me where my following numbers are wrong:

    - a 1 microsecond pulse at maximum 300 times per second would give a average ON time of 300 microseconds per second, or 0.03 percent.

    - chuck that percentage at 3 amps peak and my fingercounting results in an average DC current of only 9 mA. Noooo way it'll be bleeding 1.5 watts at that average current...


    avz10 - shut both of us up here and start changing things, willya?

    Looks like the first thing would be to get R1 down to some lower value, something between 68 to 100 ohms.

    If that doesn't help then R2.

    And hurry up, we want to see this damned thing working... :)
     

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