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[carmangary]

I don't really agree with your comment about analog drivers being more difficult to build or that the linearity is a problem. They may require an extra component or two that doesn't really raise the difficulty level. I use an analog die4drive with a ttl laser module i bought and I don't have a problem with it being non-linear. It isn't perfect but it is not noticeable for the most part.

 

[kiyoukan]

The reason i like the ttl one is it is a all in one unit.
Also i don't know if i much care for all the colors and shades that much. i liked my 7 color fusion. i know if i go for the die4driver i can chose ttl or analog but i like the simplicity of the c4r0 3 laser driver.
i know this would be asking a lot of someone but my knowledge in electronics is still very basic, if someone could mod the die4driver in to a 3 laser driver that would be amazing.
i also happen to have the plans for the 1.3 version of the driver, along with all documentation.

 

[Things]

Er, why do you need to mod it to 3 in one? How about just buying 3 drivers?

I haven't seen the price of the die4drives, but a flexmod may be another way to do it.

 

[carmangary]

Er, why do you need to mod it to 3 in one? How about just buying 3 drivers?

Personally, I like them to be seperate so that I can mount driver next to on even on the laser it controls. But, I can also understand the desire to have a single circuit board for ease of projector case fabrication.

 

[kiyoukan]

Carmangary, you it the nail on the head.
The price of the driver is 20$.
so the price for 3 is 60$.
to build it would cost around 15$ max.
Plus i want to use a quad op-amp to keep things simple and small.
in turn it will help me save some space.
off note question.
can i put a relay right before the laser diode and use it to turn on a led?
i just don't want to put one in there and have it destabilize the circuit or produce unwanted spikes and if not right before might someone suggest a better placement of one?
regarding the use of leds in my scanner here is a link to what i am also wanting to add.
http://laserpointerforums.com/f49/light-show-optics-49253.html
i want to use the modulation of the laser to control the led i do not care if the led only has TTL modulation just as that it works with the laser.

 

[Things]

LED's don't have modulation ...

Also, you can't just connect a LED to a modulation line. It will steal power from your lasers. Laser drivers are high impedance loads, ie, they only draw a teeeny bit of current from your DAC. LEDs will try draw as much current as your DAC can supply, and could kill it.

You need to use something llike an opamp or transistor on the LED's from a different power supply.

Can I suggest you do a little more reading into basic electronics before you start your build, otherwise you could end up killing expensive equipment!

 

[kiyoukan]

I do not plan to drive the leds from the lasers drivers, god no.
i want to use a relay and just use the laser power supply as the on off. the relay would turn on when the laser would. then the relay would turn on the led driver a separate thing i could also use an optocoupler.

 

[carmangary]

Do you want the LEDs to so what the laser does? Lasers turn on/off pretty fast so you wouldn't want to drive the LED with a relay. Just put a ttl LED (special LED w/ built in resistor) across the power line.

 

[kiyoukan]

yes, i want the led to mimic the lasers.
I thought i could add a cap to the led driver to slow down the rate a bit.
kinda like an overkill soft start.
i need them to be close not exact, i would not mind a small delay to promote health.

 

[Benm]

I don't really agree with your comment about analog drivers being more difficult to build or that the linearity is a problem. They may require an extra component or two that doesn't really raise the difficulty level. I use an analog die4drive with a ttl laser module i bought and I don't have a problem with it being non-linear. It isn't perfect but it is not noticeable for the most part.

Analog drivers require a full translation from dc-modded dac to current, whereas ttl just needs a comparator and a very basic on/off mechanism on the current source. That entails much more than adding one component, although it can be done obviously.

The linearity issue is more of a technical matter - you probably will not visually notice if its off a bit. On the other hand, if you were to cycle the laser from 1 to 100% intensity, you would notice the difference in color when mixing,for example, red and green. For show purposes this might not be a major problem, but it is still present, and could be noticeable when you attempt video projection or something like that.

 

[carmangary]

Building and designing are different. Designing is figuring it out. Building is putting it together. Soldering 4 components is really not more difficult that soldering on 1 component. Are you building or designing? Not sure you would want to design your own since there are several out there in schematics.

The linearity issue is there but it isn't noticeable and the difference that analog makes is worth it. You are more likely to notice the awkward steps between colors, or bright colors where it should be dim, from displaying analog frames with TTL lasers than noticing any linear problems with analog lasers. In other words, your frames will look better with non-linear analog lasers than with the best TTL lasers.

Seems like you are making it more difficult than it is and choosing the wrong answers because you think the right answers are too hard.

 

[kiyoukan]

i had a thought. (it does not happen often...)
As far as using pots go can i use the pot to find the resistance value i need on my correction amp.
then remove it and test to find out how much it resists and replace it with equal resistors.
I can get pots fairly cheap but they take a long time to get here. i can get them for around $0.25 - $0.50 each but some time take up to 45days to get here.
So i would like to not have to use them.
I know the only downside would be if i had to adjust later down the road but how common is that?

 

[Benm]

Building and designing are different. Designing is figuring it out. Building is putting it together. Soldering 4 components is really not more difficult that soldering on 1 component. Are you building or designing? Not sure you would want to design your own since there are several out there in schematics.

I'm doing both... prototyping on breadboard and then doing the build, but it starts with the design. There are some useful schematics out there, though i dont agree on all of them being the best solutions.

As for the pots: I can get the 20 turn heliotrims here for 80 eurocents each. Not very cheap for a resistor, but they make things easier compared to single turn pots for these applications.

Obviously you could first insert a pot, then measure the resistance of either end and replace it with fixed resistors. Problem is: do you have such a range of fixed resistors at hand? I' reckon it'd take a full E192 series to get close enough... or just accept that it is off a bit and correct for gain and offset from software.

 

[kiyoukan]

i think i have enough. i have over 3,000 of them i am sure i can get it close enough. a tiny bit off wont bother me.
But depending on how close i can get it i might just keep using the pots.
What do you think a close range is?
+-20ohms?

 

[Benm]

It depens on how accurate you want the output signal to be. The ilda spec calls for +5/-5 volt differential signals for the galvo controls, but i dont know what the tolerance on that is.

If your signal is a bit too low, it will result in a smaller scan angle. If it is too large, it could push the mirror to the end of its range resulting in clipping. If your amp were 10% off on the low side, you'd just end up with a 10% smaller projection... not a big problem unless you require maximum deflection for some reason.

One interesting part in the ilda specs is that all lines should tolerate input between -25 and +25 volts relative to ground without damage. I would, however, not count on all galvo drivers to really tolerate that.

 

[kiyoukan]

Just a question... if i dont need ILDA suport right now, cant i just use two correction amp circuits and pass the other ones directly to the analog drivers, setting them instead to do 100% at whatever-volts-the-soundcard-output-is?

So can i do this with the die4drivers set the max power and only use the correction amp for the galvos?
meaning i only need to build 2 circuits?
also on the schem for the correction amp i see what looks like 2 15v batterys?
i think i am reading that wrong...