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Pulsated LD

Discussion in 'General Electronics Discussion' started by Electro132, Aug 12, 2013.

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  1. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    He seems to think that a stationary laser will etch a complete image merely by some magic form of modulation. No CNC type mechanical XY control required. I also think that he thinks he can connect pickups to his head as the original image source. The computer will store the image he sees with his eyes and will send it to the laser. These assumptions are based on his last topic.

    Chris

    Dave, regarding our recent conversation. I think this will be a test of willpower and control!
     
    Last edited: Aug 14, 2013
  2. Electro132

    Electro132

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    Ok what about projectors? They project out entire images and can be altered to be brighter/darker. Here are some links

    http://en.wikipedia.org/wiki/Digital_Light_Processing

    http://www.projectorcentral.com/panasonic_rw430u_projector_review.htm

    http://reviews.cnet.com/home-theater-projectors/lg-hecto-laser-projector/4505-7858_7-35558335.html

    Lasers are used in these appliances. Somebody please pinch me. :)
     
  3. davenn

    davenn Moderator

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    laser is ONLY used in the last application

    the first 2 use high power globes shining through LCD panels/ DLP panels

    I used to repair them

    NONE of these devices are going to etch a material

    You still don't seem to understand the hi technology processes involved
    not something you can easily replicate at home and that just for a plain projector
    that last unit costs $8,999 just imagine how many millions of $$ has gone into the research and development of the device

    EDIT: and reading further, its also a DLP system where the lasers illuminate the DLP sensor ... so its NOT as tho you have a laser beam(s) scanning the projection (viewing) screen
    the advantage of using lasers to illuminate the DLP is that they last 10 times longer than globe illumination

    Dave
     
    Last edited: Aug 16, 2013
  4. Electro132

    Electro132

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    Feb 12, 2013

    You got me there. Ok, for now how about we focus on just the output then, you know, to drive a LD with 2 controllers at least. I mean i built an LD with only 1 controller - the driver so how hard must it be to just add a second controller which controls the amount of pulses the LD sends?
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Tell us about the LD you created and exactly what the controller does.
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    One of the telltale indicators of knowing too little about something is the individual usually equates it to being simple. I think it would be safe to say that a rocket scientist's first project wasn't a rocket of any sort.

    A phenomenon of the tech age is an entire generation of media coined "tech savvy" people that have equated knowing how to use technology as understanding it. Websites like ehow and instructables, with their simplistic and unverified contributions, don't help!

    Chris
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Amen Chris. Darwin put it nicely: "Ignorance more frequently begets confidence than does knowledge."
    I am amazed by the attitude of some folks. They see the latest cool device on a popular science show, and immediately assume, because they were able to follow the simple description of how it works, that they will be able to make one.

    They don't seem to realise that the device they're seeing was created through the long, hard, full-time work of many highly trained and experienced engineers, in many fields, working as a team, outsourcing work to others, and with a significant budget behind them.

    Instructables is a bit of a joke IMO. I'm just waiting for them to post instructions for how to make a DIY MRI machine :)
     
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Oh, you have them in NZ too! I have Chris' rules for many of those shows. My primary rule is the more you actually do know the less you'll enjoy watching them. Marilynne has developed a hair trigger on the remote because of me. The instant she hears me rant "That's not correct! They failed to mention that the bla bla... " ...Click; it's gone. ;)

    Chris
     
  9. Electro132

    Electro132

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    Sorry for the delayed response chaps, had work all week long. Anyway ...

    ok i had this red LD so i placed it into a driver circuit which gave an output of about 250 mA. The driver was a 100 Variable Resistor and controlled how much current would come through to the LD using 2x 10 ohm Resistor in parallel with each other coming from the output of the LM317 Voltage Regulator. This in turn would make the LD dimmer or brighter depending on how much current was coming through. Altogether i used:

    1x 100 Var Res
    1x LM317 Volt Reg
    1x LD (red)
    2x 10 ohm Res
    1x 16V 10uf Elect Cap
    1x 1n4004 Diode


    The other driver controls how many pulses are given. I have attached some pics. Also i found out a particular circuit which involved using -5 V and converting it to 3.3 V at 1A. I'm thinking that anything below zero is basically AC i assume? Anyway, here is the link for the - 5V converted to 3.3V at 1A: http://electronicdesign.com/power/simple-circuit-generates-33-v-1-5-v
     

    Attached Files:

    Last edited: Aug 18, 2013
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The second circuit you have shown us is a switchmode 3.3V regulator. It may be rated for 1A, but I don't think it has a 1A limit (in other words it may supply more and then either go into shutdown or destroy itself).

    The third circuit is poor. ignoring the diodes for a moment, the transistor's emitter should be grounded and the motor should be between the collector and Vcc.

    If you take a look at the LED tutorial there is a new addition which allows a microcontroller to switch a constant current on and off. It would probably be applicable to your apparent desire to pulse the laser diode from a 555.
     
  11. Electro132

    Electro132

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    Feb 12, 2013

    So in the first circuit, i know that P1 is a VarRes but just want to make sure what P2 (duty Cycle) is. Is P2(duty Cycle) a 555 Timer?
     

    Attached Files:

  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    The duty cycle of the left hand circuit is not variable. The author says it's 1:1 (50%) but it's not. Only the frequency can be changed by varying the value of R1 or C1. A 555 can be wired for variable duty cycle but not like that.

    The right hand circuit claims a sine wave output. That's also BS!

    Chris

    Edit: Where did you find that?
     
    Last edited: Aug 19, 2013
  13. Electro132

    Electro132

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    Feb 12, 2013

    I found it online whilst i was searching for info about the duty cycle on google.
     
  14. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    I think Chris would probably have guessed that you found it online. I think he was asking which site you got it from.

    BTW, the duty cycle of the first circuit IS roughly 50%.
     
  15. Harald Kapp

    Harald Kapp Moderator Moderator

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    Probably here.
     
  16. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Aw shucks I'd have never guessed that! :rolleyes:
    Somethings still haven't changed. It seems that no matter how many times we ask, beg or threaten,.. the cryptic responses continue! :(

    I spiced it on my other PC before I posted that. I didn't record the results but I recall Mark being about 10 to 15% longer that Space.

    Thanks Harald. Somehow you knew what I wanted. I didn't realize it was such a complicated question. :rolleyes:

    Chris
     
  17. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Sorry for not explaining myself Chris. I assumed you hadn't looked closely at the circuit and thought it was the usual arrangement using pin 7.

    The pin 2 and pin 6 threshold voltages are symmetrical around 1/2 VCC and pin 3 swings (nominally - ideally) between VCC and GND, so the duty cycle is roughly 50%. Any error is due to pin 3 not pulling up as well as it pulls down.

    How much of a problem this is depends on the type of output stage, and the loading on the output. In the original bipolar design, the output is pulled low by an NPN with its emitter grounded, but it's pulled high by an NPN emitter follower arrangement. So it will pull down very close to 0V (assuming minimal load on the output) but even with only 1 mA load, it will only pull up to about 1.4V less than VCC.

    So the output doesn't swing symmetrically around 1/2 VCC. That's why the duty cycle isn't exactly 50%. The lower the supply voltage, the more the asymmetry (as a proportion of the supply voltage) and the worse the duty cycle error.

    Other types of 555 probably have better output stages that will swing closer to the positive rail. Also, for the bipolar version, if the output is loaded heavily, the positive and negative dropout voltages will become closer to each other, because the emitter follower pulls high more strongly than the common emitter (apart from the inherent voltage drop in the emitter follower).

    So in summary, if the output stage was perfect the duty cycle would be exactly 50%. With an old bipolar 555 the output will not be exactly 50% and the error will be worse at lower supply voltages.
     
  18. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    No Kris I caught the fact that the Output pin was sourcing and sinking the RC time constant. I think my sim didn't lie it's just that I didn't set the start & end times with a settling time delay. Tina gives me 3 choices when running a Transient Characteristics..

    (1) Find Operating Point
    (2) Use Initial Conditions
    (3) Zero Initial Values

    I chose 3, which which I usually do when I sim oscillators. If I had chosen 1 I would have seen 50-50 near the end of the time sweep. I simply didn't give Tina the option of letting the circuit settle. BTW, isn't Thld more like >=2/3rds of Vcc and Trgr closer to <=1/3rd of Vcc? And yes, the CMOS (rail to rail) models do produce better symmetry.

    Chris
     
    Last edited: Aug 19, 2013
  19. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Ah, I thought the CMOS versions would be better. Yes, the thresholds are 1/3 VCC and 2/3 VCC, which are symmetrical around 1/2 VCC.
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Ah, I got ya now. It was the language barrier.. You speeking English and me speaking Chris-eese! ;)

    Chris
     
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