Lidar gun

Discussion in 'The Projects Forum' started by renduchintala, Sep 3, 2008.

  1. renduchintala

    Thread Starter New Member

    Sep 3, 2008
    Hey,please refer to this link:

    Can u explain me,

    (i) How can the LASER LED be connected,in order to provide voltage supply to it?

    (ii) How can the radar be arranged in order to attain the pistol shape?

    (iii) It is said that 9V supply is given to the RADAR and RADAR consists of LASER LED and LASER DIODE. It is again said that LASER LED and LASER DIODE must be placed in front of the radar. Can you explain me this point in detail?

    Please do spare a few minutes for me.Awaiting your reply.

  2. bertus


    Apr 5, 2008
  3. renduchintala

    Thread Starter New Member

    Sep 3, 2008
    I got u but,actually my doubt is "There is no supply to the laser LED circuit,then,how can it glow....??


    Is there any method to design the radar in the form of a pistol?

    Boss,I need to know this because i have to design the circuit on the PCB...
  4. bertus


    Apr 5, 2008

    The laser LED gets its power from the oscillator build around the 74AS04.
    ( there is no current limiting resistor used, I do not know how much current there will be).
    When you use two tubes placed above eachother (one for the laser LED, and one for the laser DIODE, so the do not see each other directly).
    This can be the loop of the "gun".
    The rest of the schematic can be build on a circuitboard in the handle.

  5. renduchintala

    Thread Starter New Member

    Sep 3, 2008
    Thanks for the information BERTUS.I am well satisfied with your points.
  6. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    Do you know this circuit works? The author doesn't show any completed hardware. If not, don't waste your time designing a PCB for it.

    The specifications of both the laser and receiver are critical to this type of application, they need to operate at very high speed and most don't. The lack of any details regarding these components or the optics makes me think that this has never been built. Also, since timing is critical, why is there no precision clock source anywhere?
  7. SgtWookie


    Jul 17, 2007
    Blocco's correct.
    This circuit was discussed several months ago in another thread. The consensus was that it was someone's "pipe dream" and had never actually been built.

    However, the author, Serge Saati, left his E-mail address in a link underneath the title. You could always E-mail him directly and ask him about it.
  8. jpanhalt


    Jan 18, 2008
    No one is sure the circuit works. So, anything is pure supposition. One problem you have to address is that the laser oscillator is not sampled or in any other way synchronized with the detection oscillator.

    Laser speed is measured with time of flight, not doppler as with radio waves (radar).

    My SWAG on the mechanism is that the laser oscillator sends on/off modulation. The receiver receives the same. If the object is moving toward (or away) from the receiver there will be a slight shift in the spacing of the received peaks from two samples, say 0.1 second apart.

    For example, assume the laser oscillator operates at 100 KHz. Your receiver detects the first transition/pulse. It then waits 0.1 sec (10K cycles) and captures the next transition. If the reflective object is going 30 m/S toward you, then in the 0.1 S, it traveled 300 cm. The reflected peak should occur 300 cm/C sooner or 10 nS sooner than expected with a stationary object. The foregoing is utter speculation and day dreaming, requires very stable oscillators, and is subject to order of magnitude errors from my rusty math.

  9. thingmaker3

    Retired Moderator

    May 16, 2005
    The oscillator providing the clock pulses to the counters is gated with the o/p of the 74AS14 at the bottom of the diagram. Those pulses will only reach the counters when the input to said 74AS14 is low.

    Now for the 64K$ question... when will said input be low?