Maker Pro
Maker Pro

Pulsated LD

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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:

Electro132

Feb 12, 2013
261
Joined
Feb 12, 2013
Messages
261
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!


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. :)
 

davenn

Moderator
Sep 5, 2009
14,254
Joined
Sep 5, 2009
Messages
14,254
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:

Electro132

Feb 12, 2013
261
Joined
Feb 12, 2013
Messages
261
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


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?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Tell us about the LD you created and exactly what the controller does.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
One of the telltale indicators of knowing too little about something is the individual usually equates it to being simple.
Amen Chris. Darwin put it nicely: "Ignorance more frequently begets confidence than does knowledge."
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!
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 :)
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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.

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
 

Electro132

Feb 12, 2013
261
Joined
Feb 12, 2013
Messages
261
Tell us about the LD you created and exactly what the controller does.


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
 

Attachments

  • Pulse output.jpg
    Pulse output.jpg
    21.2 KB · Views: 130
  • -5V to 3.3 V 1A.jpg
    -5V to 3.3 V 1A.jpg
    26.2 KB · Views: 103
  • Pulse width Modulation.jpg
    Pulse width Modulation.jpg
    12.7 KB · Views: 106
  • Square-Wave-Tone-Burst-Generator with button.jpg
    Square-Wave-Tone-Burst-Generator with button.jpg
    15 KB · Views: 82
  • voltagecontrol pwm1.jpg
    voltagecontrol pwm1.jpg
    30.6 KB · Views: 112
Last edited:

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
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.
 

Electro132

Feb 12, 2013
261
Joined
Feb 12, 2013
Messages
261
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.


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?
 

Attachments

  • 555 timer2.jpg
    555 timer2.jpg
    24.3 KB · Views: 371
  • 555-556 timers.jpg
    555-556 timers.jpg
    22.8 KB · Views: 131

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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?

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:

Electro132

Feb 12, 2013
261
Joined
Feb 12, 2013
Messages
261
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?


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

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
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%.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
I found it online whilst i was searching for info about the duty cycle on google.
Aw shucks I'd have never guessed that! :rolleyes:
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%.

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
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
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.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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:

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
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.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
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.

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

Chris
 
Top