basic laser module power/signal questions

[LaNeK779]

these pics show clearly that you need mains power to the blue/brown cables

feed 5v to the yellow cable and gnd from the same source to the black one
(or just use a couple of AA batteries for 3volts, should give you 60% of the modules power)

[LaNeK779]

when frames are being projected the beam flickers (don't expect to "catch" the fast modulation changes by naked eye, too damn fast).

flicker depends on the frame being projected (blanking etc)

[LaNeK779]

well, this question is more complicated to answer

it is believed (and often found out) that all sorts of DACs when sending signals, do not put out the full 5volts needed, so you might still not see full power even when projecting one dot

I remember someone saying that you need to overlay several dots to get something close to full power. so how is this "one dot frame" made?

[norty303]

It is nothing to do with the DAC sending the 'right' signal. It is due to software design.

If your software has a minimum point setting of 100 and you add a single point, you get one point on, 99 points off, for that frame, so it looks dim. If you add 100 points, you get none off and all on so its bright. Simples.

Minimum and maximum points settings are there for a reason, but you can fiddle with them if you want to.

If its Pangolin, I think if you hold CTRL of shift or something when you create the point it does it in 25 point increments (or something like that - maybe 100, its been a while....)

[norty303]

I suspect he is referring to the practise of people measuring the blanking output with a multimeter, rather than a scope.
Some DACs have a very short period of 'housekeeping' each processor cycle, where they go off, even when projecting what you would perceive to be a constant beam.
Any measurement with a meter is going to only show an average voltage, which is why people thought that they gave less than 5V.
When measured with a scope, they can clearly be seen giving the full 5V, albeit with period when they're off for various reasons, including blanking in the test frame.

If you really want to go over it, do a search for dacs not giving 5v, and you can lose some hours of your life with various debates that went on.

You mention testing yours with a multimeter. Go ahead, and you'll probably see less than 5V, depending on what you're projecting, and with what DAC/software. Even one of the most 'on' patterns (the Lasermedia test pattern) has some bits off I believe, but as it features redraw lines is the one I usually use for power testing if I haven't got a 5VDC source handy.

[norty303]

Its a very short time in each cycle, which is in itself a very short time. Whilst its probably measurable, I doubt you'd be able to detect it with your eyes.
Really, the days of worrying about this stuff should be over. Power is cheap, and if you're worrying about the tiniest bit of brightness, just buy a bigger laser module.
Now we're into 0.5W modules or greater as a minimum a lot of the time, a very small dip in power shouldn't be a problem, especially with DI modules, where rise times are much better than with DPSS.
I doubt many/any on this forum could tell the difference between 900mW and 1000mW coming out of a module with their eyes.

[frostypaw]

Might be wrong but the answer I think you want lies between the lines there - yes you will see a drop in the power just projecting a dot, but it's easy to change the ratio between the blanking time and the drawing time by placing extra dots on top of each other so you reach the point where your eye can't really tell the difference.

At the risk of patronising if a 0 is the laser outputting and . it blanking then with a single dot in a theoretical super-simple projection you'd be seeing
0.0.0.0.0.0.0.0.0.0.0.
but place three bright spots on top of each other in the frame and you see
000.000.000.000.000.
and because your eye's response isn't linear you can't tell that from
00000000000000000

Persistence of vision is amazing and the whole projection thing relies on it. I'm pretty sure it's a very different experience for other animals - the cat is utterly riveted by what appear to be static patterns to me.

[frostypaw]

That's exactly what I was trying to answer..... guess I ballsed that up.

edit> what I tried to explain poorly was yes, but the non-linear way your eye responds to brightness makes the effect negligible if you tilt the ratio of on/off the right way

[frostypaw]

the right way ?

As in closer to being constantly on.

Like norty was explaining there's always cycles in a DAC's output where the laser is off, but if the ratio between on and off is closer to 'on' than 'off' the brain takes it as 'on' which is the bit I was trying to explain with the 0's and .'s. A laser power meter would probably confirm you're only looking at 3/4 brightness, but the eye can't tell.

I guess closely related to why you can't determine laser output by comparing against another, we're just not very good at it.