Question with Flexmod P3 setup

[KANG]

Hey all, just recently purchased 3 Flexmod P3's from Innolasers and the RGB DTR bundle I was convinced this is the way to go in terms of modulating the lasers. I'm very intrigued with the idea of DIY. Although I'm very good with mechanical processes, fabricating, machining etc... I do lack the electrical side of things which is where I need some help! I read through the instructions on setting up the Flexmod and Swamidog gave some very insightful information which I greatly appreciate.

One thing I failed to recognize is the beam suppression kit. http://www.photonlexicon.com/forums/...hlight=flexmod What does this mean? Does this mean You can have one or two lasers on and suppress the output of the other beam? I'm more interested in beam shows than anything. If this is not a huge problem I would like to know. If what I said above is correct about beam suppression. Can you modulate the beam to have a low current/dim light so that it is nearly suppressed?

What does interlock do? (It allows the current loop to the diode to be closed in order for modulation? Is this correct?) The Bias initially starts at 0 which means no current passes through the diode and if interlock is not closed then the RED LED comes on hinting something is not wired correctly.

0 Bias? I think I read somewhere that this potentiometer needs to be turned so that it is just under the threshold of the diode? (I.e. just under 1,000mA?) Does this allow maximum efficiency of the beam? I am a little bit skeptical of running too much current, I feel like I would be breaking something.. :/

I do not quite understand what the gain pot does. Does this run with respect to the Bias Pot? How do these two relate?

Lastly, for balance? Does this not need to be changed if we have a very precise power source? How will I know when to use balance?

I noticed that the flexmod setup for laser pointers at LPF was very clear and made a lot of sense to me. But, this is a different setup than a projector.
http://s187.photobucket.com/user/mag...40d0f.jpg.html I saw this picture thanks to andy_con and it makes a lot of sense! Any additional pictures or circuit diagrams would greatly help!

My understanding on wiring thus far:
I see that the diode connects to the + and - of the flexmod P3 seems simple enough, the power supply (gnd) shares a point with the modulation (gnd) of the ILDA board, the 5v+ modulation connects to either (green, red, blue labels on the ILDA board), and then the 12v+ is from the power supply which is also shared with the interlock. These connections seem to make sense, however correct me if I am wrong please as I am learning!

As for setting up Flexmod P3 I read through the forums and saw a few other people having difficulties trying to set things up.
http://www.photonlexicon.com/forums/...hlight=flexmod
I have been reading carefully to try and understand some of the terms and where wires are suppose to go but am struggling.

Things that may help. I have access to good soldering/electrical equipment/supplies (resistors, wires etc) . Single output DC Power supplies, Digital multimeter, Digital Oscilloscope etc.

~I appreciate all your continuation to be patient with me on my project this is all very intriguing/addicting I can't wait to keep continuing with this! Thank you all, let me know if there is anything else I can do. Theo

[dkumpula]

One thing I failed to recognize is the beam suppression kit. http://www.photonlexicon.com/forums/...hlight=flexmod What does this mean? Does this mean You can have one or two lasers on and suppress the output of the other beam? I'm more interested in beam shows than anything. If this is not a huge problem I would like to know. If what I said above is correct about beam suppression. Can you modulate the beam to have a low current/dim light so that it is nearly suppressed?

Hey Theo!

No worries. Good questions that we all have to figure out on our first builds. First, did you buy the P3 with the beam suppression option or not? The P3 comes in two options. The beam suppression option has different firmware installed on it and requires two small resistors to be soldered on to some very tiny points on the board. (I find it to be some tricky soldering.) If you didn't order the slightly more expensive beam-suppression option, then you follow the directions for wiring the interlock connection differently and don't have to the additional resistor soldering.

To answer your question(s) though. Beam suppression simply turns off any bias current to the diode. I believe this does this when modulation voltage is below 0.4V or something similar. People choose beam suppression for diodes that have an bright LED glow when the bias is set close to the lasing output. In some cases, such as some of the 520nM green diodes, they sometimes do the LED glow (or even lase a bit) even when bias is turned all the way down and modulation voltage is zero. Beam suppression is designed to resolve this. If you don't have beam suppression P3s, you can usually turn down the bias further to decrease the LED output below the point that you find it irritating when its not lasing. On a low output kit like you are working with, you shouldn't have a problem with the LED glow when Bias is near lasing threshold on at least your red or and blue.

What does interlock do? (It allows the current loop to the diode to be closed in order for modulation? Is this correct?) The Bias initially starts at 0 which means no current passes through the diode and if interlock is not closed then the RED LED comes on hinting something is not wired correctly.

The interlock is a safety feature. If the interlock loop is open, the P3 won't send any current to the diode regardless of what the modulation voltage is. The red LED on the P3 glows when the interlock loop is open or it detects an open loop on the diode circuit. Interlock protection and open loop detection are not available by definition in the beam suppression version.

Bias is simply a threshold current for the diode (when modulation voltage is at zero) so you get nicer analog ramp-ups in your output from the diodes. Many diodes have a slightly different lasing threshold when warm vs cool. You will want to ensure that you test it to ensure you set it below the point where the diode starts lasing. A half a turn down further than the lasing threshold when the diode is warmed up generally does it for me. Or you can turn it off and wait for it to cool down and see if it lases when you turn your pj back on.

0 Bias? I think I read somewhere that this potentiometer needs to be turned so that it is just under the threshold of the diode? (I.e. just under 1,000mA?) Does this allow maximum efficiency of the beam? I am a little bit skeptical of running too much current, I feel like I would be breaking something.. :/

Turn the bias pot all the way down (counterclockwise) 40 revolutions or until it starts clicking. As described above, you'll only turn it up to the point close to the lasing threshold. Additional instructions further below.

I do not quite understand what the gain pot does. Does this run with respect to the Bias Pot? How do these two relate?

Gain defines the max current that the diode receives when mod voltage is at 5.0V. If you set this too high, you turn your laser diode into an LED and ruin your day. Modulation voltage tells the P3 how much current to output to the diode between low end (the bias current) and the high end (the max gain).

Lastly, for balance? Does this not need to be changed if we have a very precise power source? How will I know when to use balance?

Don't change this in most circumstances. It is intended to address power supplies that vary greatly in voltage which apparently results in odd bias behaviour. (I've never had such a power supply, so I don't know what other problems may arise that the balance may address).

My understanding on wiring thus far:
I see that the diode connects to the + and - of the flexmod P3 seems simple enough, the power supply (gnd) shares a point with the modulation (gnd) of the ILDA board, the 5v+ modulation connects to either (green, red, blue labels on the ILDA board), and then the 12v+ is from the power supply which is also shared with the interlock. These connections seem to make sense, however correct me if I am wrong please as I am learning!

Yes, that all looks right.

You can set up the current adjustment as described in the P3 directions, but I do things a little different (and easier IMO), but it requires a laser meter. If you don't have one, ignore the rest of this. If you do, this is my process for a standard P3 without beam suppression.

1. Before powering up the first time, turn down both the gain and bias pots all the way (counterclockwise 40 revs or until they click).
2. Short diode output leads momentarily.
3. Connect the diode.
4. Turn on power to the P3. Leave modulation voltage at zero for now. (e.g. Don't play a show). There should not be a red light on the P3. If there is, you have an open interlock, the diode is not connected properly or you have some other type of error.
5. Slowly turn up the bias pot. You'll see the diode begin to glow at some point (usually within a few turns). If you are making lots of revolutions up on that pot and don't see output from the diode, you probably have something wired incorrectly. When it lases just above that threshold, adjust your collimating lens if necessary. Then turn the bias back down about a half turn to get back to a low LED glow (or further if you prefer).
6. Send +5V modulation. You can do this with a 5v DC transformer or if you already have everything wired up, send it a frame with that color on for a lot of points (e.g. a circle with 500+ points on it). It may only get you to ~4.8v, but that will get you about as close to 5V as your DAC and SW are likely to allow when playing a show.
7. Start to turn up the gain slowly with a laser power meter measuring the output. It may take your power meter a couple seconds to accurately measure the output, so go slow.
8. The most important thing is to not set the gain too high. I tend to use the high quality G2 collimating lenses so I'm generally assured of not losing much of my diode's potential output. The diodes have a rated output, of course, but I'm sure you've read that many of the diodes can be pushed further - potentially at the expense of the diodes longevity or immediate death. I watch the power meter carefully as I get nearer to my target output. When a half turn doesn't increase the output very much (or if it starts to drop) you are near (or over) the peak output for the diode and you should turn back the gain. The diode will be getting warmer here and you may see it dropping a few mW below its max, but you want to choose a point where the output is generally quite stable. Personally, I tend to not push my diodes too hard - generally setting them halfway between rated max output and the max output published by DTR or others. If you use a 3 element or other glass lens, I believe you'd want to set them even lower.

IF YOU HAVE THE BEAM SUPPRESSION VERSION: My approach is the same, but you have to give it a bit of modulation voltage (e.g. 0.4v) before beam suppression is turned off. You can then set the bias to the correct level and proceed on to adjust the gain.


Finally, for the record, the current adjustment approach in the P3 instructions (as opposed to the instructions above) is the safer and correct way to set the P3 and doesn't require a laser meter. I just thought I'd share my alternative approach as its worked for me for my past 8 builds with no associated failures.

Good luck and have fun!

-David

[JasonB]

David, that is a great post. Even though I've set up a couple P3s without beam suppression and one with I had some similar questions. My experience has been that I can get the LD to turn all the way off with the suppression feature but I still have some ghosting with the non-suppression versions.... I'll try your method of set up! Thanks...

Kang, often other folks have the same questions, thanks for posting!

-Jason

[dkumpula]

My experience has been that I can get the LD to turn all the way off with the suppression feature but I still have some ghosting with the non-suppression versions.... I'll try your method of set up! Thanks..

Thanks for the kind words, Jason! I can't get rid of a very low lase using the 520 nm 120mW without using a beam suppression P3. I also prefer the beam suppression model for the 170mW single mode 638nm reds as they can be quite bright as an LED when they get close to lasing.

-David

[KANG]

Hey Theo!

No worries. Good questions that we all have to figure out on our first builds. First, did you buy the P3 with the beam suppression option or not? The P3 comes in two options. The beam suppression option has different firmware installed on it and requires two small resistors to be soldered on to some very tiny points on the board. (I find it to be some tricky soldering.) If you didn't order the slightly more expensive beam-suppression option, then you follow the directions for wiring the interlock connection differently and don't have to the additional resistor soldering.

To answer your question(s) though. Beam suppression simply turns off any bias current to the diode. I believe this does this when modulation voltage is below 0.4V or something similar. People choose beam suppression for diodes that have an bright LED glow when the bias is set close to the lasing output. In some cases, such as some of the 520nM green diodes, they sometimes do the LED glow (or even lase a bit) even when bias is turned all the way down and modulation voltage is zero. Beam suppression is designed to resolve this. If you don't have beam suppression P3s, you can usually turn down the bias further to decrease the LED output below the point that you find it irritating when its not lasing. On a low output kit like you are working with, you shouldn't have a problem with the LED glow when Bias is near lasing threshold on at least your red or and blue.

-David

Hey David, thanks for your great response! I read through all of you responses to my questions. I'll probably have to read through all of it again a few more times so I can grasp the concepts a little more. I am currently home for the weekend so I don't have any of my laser stuff with me. I will throw up some pictures of the wiring that I have as well as some of the digital readings and any questions that may come up with that. Thank you for your helpful response. I'll keep you guys updated on what I do possibly in next few days!

As for beam suppression I do not have that option which I think I should be okay unless I decide to upgrade or build something with a little more power.

[kecked]

How does beam suppression work compared to a shutter? Not tech wise but image wise. Does suppression mess with the low end brightness colors? IE does it trip quick enough and low enough that you can still do faint colors? Wonder if an electronic shutter exists that would work like a simple aom but be on and off.

[KANG]

I got my blue laser module working! I followed the P3 instructions closely. The red diode never went on which was a good sign so I got my circuitry correct. I did some tests using between like 9-15V on a varying DC power supply. The instructions said to have a standby current of around 50-150mA I left it around 80mA or so, not sure what is really optimal. I did get the the diode to lase and tried different current settings causing it to get brighter/dimmer respectively. It was a good day I didn't have enough time today to do the red or green modules I'll probably work on them after Thanksgiving break when I go home to get my power supply for them as well as their aluminum housings. This is really exciting things are becoming functional! Thank you for all your help guys. And @ dkumpula I'll probably get a laser power meter also for future testing.

~Theo

[dkumpula]

How does beam suppression work compared to a shutter? Not tech wise but image wise. Does suppression mess with the low end brightness colors? IE does it trip quick enough and low enough that you can still do faint colors? Wonder if an electronic shutter exists that would work like a simple aom but be on and off.

I think I can answer at least some of this, Kecked. At least with the P3, beam suppression kicks in when modulation voltage drops below a certain threshold. I believe that threshold is approximately 0.3V on the P3. So assuming you had a perfectly linear ramp-up on your driver, you'd effectively lose whatever low end range you had between 0V and 0.3V, although you may be able to compensate by turning down standby bias voltage a little bit. That said, I doubt that perfectly linear low end modulation is achievable although you can certainly get better match-up between diodes with DZ's color board.

How fast is a question I can't answer. Its fast enough that you don't notice a low-end lase after mod voltage drops below the suppression threshold, but I don't know if its milliseconds or microseconds before it kicks in. In either case, I'd assume faster than a good mechanical shutter.

Speaking of shutters, there was a discussion at ILDA this week after someone was having trouble getting the projectors there to respond timely. Apparently shutters may be treated differently between DACs and/or software packages. For example, with LSX in combination with an Etherdream DAC, as soon as you hit play on a show, Pin 13 voltage flips to +5V to open the shutter and continues to hold at +5V until you stop the show (i.e. pausing the show in the middle does not close the shutter). In another package (I don't recall which) it appeared that the shutter voltage didn't go to +5V until each cue was triggered - causing shutters to keep opening and closing (which made it nearly impossible to run cues in a live environment). I think this was an issue with a Moncha DAC. This may have been related to the gentleman's controller as well, but I thought I'd mention it.

-David

[Zeppelin1007]

So i hate to be THAT guy that makes his first post one that bumps an old thread,

But,

The Manual says " If ordered, your driver is capable of suppressing the standby glow", and "To enable this feature, " leads me to beleive i dont HAVE to enable beam suppression?

is this true?

Meaning, does this thing operate like a normal Flexmod until the resistors are attached? in which beam suppression becomes active? thats how i take it given the above parts from the manual.

Hint: I cant set the output current no matter what the heck i do lol. Red Led is always on. Meter lets me adjust standby...oh and it does it so smoothly

I'm so close! been working on this project awhile now. All i need is to see this baby turn on!

Thanks in advance!

[dkumpula]

The Manual says " If ordered, your driver is capable of suppressing the standby glow", and "To enable this feature, " leads me to beleive i dont HAVE to enable beam suppression?

is this true?

Meaning, does this thing operate like a normal Flexmod until the resistors are attached? in which beam suppression becomes active? thats how i take it given the above parts from the manual.

Hint: I cant set the output current no matter what the heck i do lol. Red Led is always on.

The Flexmods with the beam suppression option have different firmware and have some traces cut (you'll see a scratch on top of the board near the Interlock solder-pad as I recall). That said, I've always attached those tiny, tiny resistors to their tiny, tiny locations immediately, but the interlock error you are getting doesn't surprise me at all.

More importantly, why would you buy the more expensive beam suppression Flexmod and NOT want to have beam suppression?? If you don't want beam suppression, buy the cheaper Flexmod!

-David