TTL/Analoge drivers?

[Shysk]

Hi , this is my first post here.
I am a newbie on the laser scanners so, i wanted to try it.
I will start with those cheap galvo kits available on pages like alliexpress/ebay/banggod.Also an helios DAC. And when i get some experience i will go for better quality components.
My question is, i've found a bunch of laser drivers in those pages, for TTL modulation, but as i know, for a laser scanner i need an analoge driver, so the main board can configure a full color palette.
So, is there any way for knowing 100% that these drivers are analoge and not ttl? Could i get links for analoge drivers, or, a blueprint for making one by myself?
https://www.ebay.com/itm/2A-635nm-68...8AXm:rk:7:pf:0
I ask it cause sometimes i see "Analoge TTL modulation" On the tittle so i don't want to receive a TTL one

Greetings, and thanks for replying, have a nice day

[swamidog]

i strongly recommend drivers from forum member BBE.

His drivers are analogue and really excellent:

https://www.ebay.com/sch/x-wossee/m....p2047675.l2562

Hi , this is my first post here.
I am a newbie on the laser scanners so, i wanted to try it.
I will start with those cheap galvo kits available on pages like alliexpress/ebay/banggod.Also an helios DAC. And when i get some experience i will go for better quality components.
My question is, i've found a bunch of laser drivers in those pages, for TTL modulation, but as i know, for a laser scanner i need an analoge driver, so the main board can configure a full color palette.
So, is there any way for knowing 100% that these drivers are analoge and not ttl? Could i get links for analoge drivers, or, a blueprint for making one by myself?
https://www.ebay.com/itm/2A-635nm-68...8AXm:rk:7:pf:0
I ask it cause sometimes i see "Analoge TTL modulation" On the tittle so i don't want to receive a TTL one

Greetings, and thanks for replying, have a nice day

[buffo]

So, is there any way for knowing 100% that these drivers are analoge and not ttl?

If you're buying from aliexpress or banggood, you will probably end up with a TTL driver. At the low end of the market the suppliers will do anything to shave the cost of the driver, and making it TTL only is one way they do that. Of course, then they have to get "creative" with the marketing language so people will buy them...

As suggested above, the BBE drivers are reasonably priced and have been used by many of the users here for their home-build projects with great results.

Adam

PS: Welcome to PhotonLexicon!

[Shysk]

Hi!
Thanks for the answers , i am checking them. So, i should buy three of this one, right? ( https://www.ebay.com/itm/L5000TG-5A-...IBKj:rk:1:pf:0 )
The unique thing is that i don't see any output voltage for the laser diode.
I also wanna know if there is any any math method for knowing how much mW i need for each diode. For example, for a 1W scanner, the mW of each diode for a good white color.

Have a nice day!

[buffo]

The driver you linked to is designed for high-speed TTL modulation only. (Pulse-width modulation) What you want is a driver that support *analog* modulation. If it also says it supports TTL and PWM, that's fine, but it needs to say analog.

This is a better choice: https://www.ebay.com/itm/3A-analog-l...n/163377518563

Note, however, that the exact driver you purchase depends on which diode you will be powering. A low power single-mode red diode has about 3.3 volts across the diode and maxes out at 350 mA. A 1 watt multi-mode red diode actually drops less voltage across the diode (~2.6 volts) but pulls a lot more current (1.5 amps). High power multi-mode blue diodes drop around 4.6 volts across the diode and pull over 4 amps of current. Look up the maximum current for the diode(s) you'll be using, and also check to see what the forward voltage drop is for each one.

Ideally you want the maximum current for your diode to be within the band of 50%-75% of the max current of your driver. The driver I linked to will max out at 3 amps, so it's not going to be able to run a high power multi-mode blue diode at full current. And likewise, if you are using low-power single-mode diodes, then the max current draw would be about 10%-15% of the driver's maximum, which is not optimal either. (But single-mode diodes are often used in groups, so if you have multiple diodes in parallel they can be powered from a single driver. If you do run them in parallel though, it is a good idea to install a current-balancing resistor in series with each diode. Something like a .5 ohm 1/2 watt resistor is plenty.)

In selecting the driver there are two main concerns: 1) the maximum current draw of the diode 2) the forward voltage drop across the diode. As discussed above you want some headroom (at least 25%, but ideally not more than 50%) in the driver above this limit. With respect to forward voltage this simply dictates how much voltage you need to supply to the driver. Most drivers need at least 1.5 volts above the maximum forward voltage drop across the diode. You can go higher of course, so long as you stay below the maximum rated input voltage for the driver. But higher input voltage to the driver means more heat will be generated by the driver.

Thus, for low power, low forward voltage drop applications it's common to see 5 volt power supplies used, while higher power solutions for multi-mode blue and green diodes (which have higher forward voltage drops) you will usually see 9 or 12 volt supplies used.

There is a final consideration that is often overlooked: heat. Take your input voltage, subtract the forward voltage drop across the diode, and multiply the result by the maximum diode current. This will give you maximum the heat (in watts) that the driver will generate when operating. (If you are running multiple diodes in parallel you need to add the maximum current for each diode to get the total current through the driver.)

Now, if you already have the heat sink tab from your driver mounted to a large heat sink (like the baseplate in your projector), then you don't need to be concerned. But if you're only relying on the tiny heat sink that came with the driver, you really need to check the spec sheet to be sure you're within the heat dissipation abilities of that heat sink.

Adam

[Shysk]

Hi,
Thanks for the explanation!!
However, i have a few questions.
As u said, if the diode uses 15% of the total driver power, it´s not optimal either cuase it´s not worth buying it or because of the driver itself?.
So, i can use the driver that i shared, but it´s better i buy the one u shared cause it´s only analoge and with better specifications?
Is there any formula for knowing how much mW/W i need for each diode for making a pure white? I mean, the different wavelenght and visibility?
Thanks again, and have a good day!

[buffo]

if the diode uses 15% of the total driver power, it´s not optimal either cuase it´s not worth buying it or because of the driver itself?

It's not the power rating, it's the *current* rating. And the driver may be just fine otherwise. But if it has a maximum current rating of 3 amps and your diode only draws 300 milliamps, then it's not going to work well. This doesn't mean the driver is bad, it just means that it isn't the right size tool for the job.

I can use the driver that i shared, but it´s better i buy the one u shared cause it´s only analoge and with better specifications?

The driver you shared does not support analog modulation. So you will not be able to dim the laser diode. It will be full on or full off.

For laser shows, you really want the ability to smoothly dim the laser from full brightness to completely off. Otherwise you will only have 7 total color combinations: Red, Green, Blue, Red+Green (Yellow), Red+Blue (Magenta), Blue+Green (Cyan), and Red+Green+Blue (White).

This video shows what I mean: https://www.youtube.com/watch?v=ib83vbeqrXc It's not my video, but it's a pretty good demonstration of how much you lose with TTL-only modulation. (Note that most of the blue is completely lost in the lower image because the blue intensity is faded down below the turn-on point for TTL throughout most of the show.)

Is there any formula for knowing how much mW/W i need for each diode for making a pure white? I mean, the different wavelenght and visibility?

There are as many answers to this question as there are people on the earth! Seriously though, there are some rough guidelines, but the problem is that color perception is subjective. Thus everyone has a different idea of what a proper "white" should look like.

And yes, you can calculate the ideal white based on the C.I.E. color chart and the wavelength of the lasers you have in your projector, but even if you do that there is no guarantee that you will agree with the results of that calculation. Some people like a lot of red in their white, while others prefer a white that has more blue in it. So people will always argue about what constitutes a "perfect" white.

A while back one of our members here actually produced a software tool that would do this color balance calculation for you. And that tool became the focal point for countless arguments about what looked good and what didn't! Seriously - there are lots of threads here where this comes up. Just search for the terms "color balance" and "chroma", but be prepared for a lot of drama!

So take any advice you get on the subject of color balance with a grain of salt. (And I include my advice in that mix! My color preference is almost certainly going to be different than yours.) That being said, if you assume 638 nm red, 520 nm green, and 445 nm blue, a good starting point to get 1 watt of white would be 300 mw red, 200 mw green, 500 mw blue.

To be honest, these days most people just say "to hell with the calculations" and simply use a 1:1:1 ratio because power is so cheap. (So 333 mw red, 333 mw green, 333 mw blue for the above example of 1 watt of white.) So long as all your laser diode drivers support analog modulation, you can tweak the color balance in software to match whatever your personal preference is.

Adam

[Shysk]

Hi,
Thanks for your reply
I'll take that and what y said in your last reply too before buying a driver.
One more thing; are PWM and analoge the same? I mean, i need an analoge PWM driver
Also, if I am using an SD card with ild files, can the projector play an entire show from it?
Thanks and have a good day

[lasermaster1977]

Hi,

One more thing; are PWM and analoge the same?

Sorry, no. PWM is a digital signal format where the pulse width varies while the pulse frequency remains the same and the signal pulse amplitude at any time is either 0v or 5v. Analog in the laser diode world is a signal that can vary in voltage value in any way at any time from 0v to 5v.

I hope this explanation helps.

[VDX]

... some vendors use a capacitor to tweak a PWM-output to "cheap anlogue" - it's simply "averaging" the PWM-pulses with the capacitor, so the pulses and pauses between average to a (rippled) voltage, defined by the PWM ratio.

For slow timing applictaions this behaves like an analogue voltage -- but with the used capacitor value it's either super slow in reaction time (ON/OFF-timing depends on capacity), or it's "rippling" badly

Viktor