infra red circuit help

Discussion in 'The Projects Forum' started by stevy123, Mar 20, 2008.

  1. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    Hi All

    I am currently building an infra red transmitter circuit using an OD50L and a IRLZ34N fet.

    I have been reading that the od50l can sustain 10A when pulsed at a 10% cycle rate. Up to now i have just been running off a power supply at 12 volts with this circuit.

    What i would like some adivce on is how to create a circuit that can produce a 10A pulse to give me the distance i require? Anyone and ideas? What sort of power supply circuit would i need to build?

    Thanks in advance steve

    http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=od50l

    http://uk.rs-online.com/web/search/...)&Ntx=mode+matchallpartial&N=4294955188&Nty=1
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    It is important that you consider your IR link as a system. That means that the receiver design will play just as key a role in the overall performance as the transmitter.

    The more sensitive your receiver is the less power you will need to trigger the detector.

    Are you looking to send data over the link or are you just looking to detect the IR beam is blocked or unblocked?

    hgmjr
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    The data sheet says a 10uS pulse @ 400 Hz with 10 amps. That's a .4% duty cycle. Rather than fry the emitter, you might think about rigging up a parabolic reflector to help with distance.

    The OD-50L drops 1.65 volts when forward biased. That leaves 10.35 volts out of your supply to push current. If your supply is good for those 10 amps, you may have already cooked the IR diode. Once you have put enough voltage across a diode junction to start conduction, there is no mechanism in the device to limit current. Some means, like a resistor, has to be used.

    The dissipation limit is 1 watt, so a heat sink is in order. You can get finned collars that fit TO-39 cases.
     
  4. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    Hi

    I am not sending any data across the link, just wanting to know if it is recieved or not. I need it to work over a distance of around 30 meters.

    On the detection side i am using this photo diode connected to an op-amp to measure the recieved signal.

    What way should i build the circuit? What other componets would i need? Anyone any ideas on how my circuit diagram should look? Should i use a 555 timer to pulse it on and off? Any help greatly appriciated.
    steve
     
  5. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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  6. Audioguru

    New Member

    Dec 20, 2007
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    The 0.4% duty cycle at 400Hz is for a max time of only 10 seconds.
    The datasheet has a curve that shows how quickly it "degrades" with a current that is much less than 10A.
     
  7. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    Would it be ok to run it at 10A and have it on for a second off for a second? Pulsing it that way? Or would it need to be off for longer?
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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    You will definitely want to avoid leaving it on for more than a few milliseconds at 10A.

    hgmjr
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    If you are looking at getting high pulse currents for short periods, I would look at a mosfet driver.

    John
     
  10. hgmjr

    Moderator

    Jan 28, 2005
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    Turns out the poster has indicated that he is using a IRLZ34N. This is an n-channel mosfet driver.

    hgmjr
     
  11. hgmjr

    Moderator

    Jan 28, 2005
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    If you proceed with this project, I would caution you to be very careful when soldering the optoelectronic components. They are easily degraded by exposure to high temperatures for even brief intervals of time.

    hgmjr
     
  12. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    The IRLZ34 is a logic level fet. I was talking specifically about a mosfet driver to give the required short pulse for the IR emitter.

    John

    Edit: I guess "mosfet driver" could mean either something that drives a mosfet or somehting that uses a mosfet to drive something else. It's kind of like Monty Python's take on "wet paint." I meant the former.
     
  13. hgmjr

    Moderator

    Jan 28, 2005
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    Good point, that would likely provide the narrowness of pulsewidths and thus minimize the risk of damage to the device.

    My preference in this case in order to achieve the distances of 30 meters would be to use mulitple transmitters and pulse them at a lower power. I would even consider the use of a focusing optical lens close to the detector to enhance the sensitivity to the pulses from so far away.

    hgmjr
     
  14. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    Hi All

    Thanks for your help, ive been looking at mosfet drivers, would this be a suitable one to use?

    http://www.farnell.com/datasheets/99115.pdf

    the ICE3A1565 — INFINEON — MOSFET, INTELLIGENT DRIVER

    What other componets do i need to set this up? im new to electronics design so please excuse all the questions.

    I think running at 10A is very high so was going to try running at 5A and see if i can get the distance? What do i need to set up to use this mosfet driver and my od50 to get this working? Anyone know what the circuit diagram would roughtly look like?

    Regards
    Steve
     
  15. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That device has an integrated mosfet and PWM. It is also 34 pages of datasheet --developers must get paid by the page.

    I was thinking of something a bit simpler, such as the Max4420 series of drivers with just one wire in, one wire out, and a 6-page datasheet.

    Here are some other thoughts. Are you going to use a micro to control it or analog devices? Do you intend to have periodic short bursts or a continuous, low-frequency but very short duty cycle driver? Finally, have you considered the near UV (350 to 400'ish nm)? Near UV might be easier from an optical standpoint and is not attenuated in air. John
     
  16. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    I need it to send out short periodic bursts, was goin to maybe use a 555 timer to do the burts? Not really sure. No the system that i am using needs to use infrared.

    What all would i need to use to set it up for on a second off a second type of thing?

    Regards
    steve
     
  17. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    If you are up to it, I would suggest a small micro rather than a 555. Good learning experience and far fewer components.

    If you go the 555 route, consider the 556. Use one-half to create the short pulses and the other half to create the bursts. There are many circuits out there for modulating an IR carrier like I just described. John
     
  18. gee_emm

    Active Member

    Jan 16, 2008
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    it hasnt been mentioned yet, but IR laser diodes, or even green lasers taken down to IR, will give you a great distance. But then youd still have to work on its on / off times you need.
     
  19. Søren

    Senior Member

    Sep 2, 2006
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    Hi,

    30m can be reached with much less current than what you propose.

    The beo4 and similar remote controls from B&O can go this distance IIRC, although who'd need that unless they had a really-really huge screen ;)


    Using the emitter you have with 500mAh pulses gives an output of 500mW/sr @ 880nm.

    The integrated IR-receiver, TSOP4838, will have close to than 80% of it's peak sensitivity at 880nm (peak=950nm), which equates to a bit more than 30m minimum distance in free air (around 45m typ. dist. in free air and almost 65m typ. dist. in a corridor), so this should provide you with ample range.
    And this is just a single component the size a bit larger than a TO-92.
     
  20. stevy123

    Thread Starter Active Member

    Nov 19, 2007
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    Hi All

    Thanks for your replys,
    have drawn up a few circuit diagrams of what i think my transmitter and reciever should look like.

    I am going to order the TSOP4838 and use it as the reciever.

    Can anyone tell me if my circuit diagrams look ok or what i would have to do to them to make them work as expected.

    The 555 timer circuit i have calculated to give me a 0.5 second on time 0.5 second off time feeding the IRLZ34 and therefore pulsing the od50?

    Should this work or what should i do to make it work?

    Link to circuit diagram
    http://i274.photobucket.com/albums/jj266/sjfphones/circuit1.jpg

    Regards
    Steve
     
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