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Thread: Cambridge scanners

  1. #11
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    Quote Originally Posted by Pangolin
    Despite the 50% reduction in number of damping controls these are a whole lot easier to tune.
    That makes sense; there's fewer pots to adjust. But was making them "easier to tune" the ONLY reason the extra controls were removed?
    This is a major improvement in usability by end users, who are (far more often than not) non-technical.
    What was sacrificed in terms of adjustability to gain that "major improvement in usability"?
    Basically, this is a trouble-free 30K scanning system, that can scan a full twice as wide as an equivalent 6800 or 6210 system with the same imagery.
    Do they still sell the old amp design (the one with the extra tuning pots), or is this now the only amp available?

    Adam

  2. #12
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    I wish I could fly over there for the pre-SELEM meeting

    Have read alot of the CT6215. What price range is for a complete system?
    I guess it will take me month to get a pair of this...when I got money...say next year! hehe

  3. #13
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    (Just posting before i run off to do the new years 8pm in cali right now)

    What was sacrificed was the last 10% of scanner performance. (number came out of my ass)
    To me, that's the difference between "meh" and "wow".

    For a 6215 set for entertainment, you're looking at between $1.2k-$2k depending
    on quantity and what you want... The scanamp you select gives the most variability
    in pricing, but there are submodels with different behaviors.

    Bill: :twisted: Gah! So they INTENTIONALLY removed the scale! !@#@!#
    As in, actual THOUGHT went into this process!!! :evil:

    Last year, we were building a row of scanners and one of them ended up
    with a slightly smaller scanangle, "no problem" I thought, a quarter twist
    of the knob will bring it right up... Instead! I had to make a small PCB with
    TL074s and an asspack of resistors to sit between and externally increase the gain.

    Regarding doubling up on knobs, that's the same compromise you see on only
    the lowest end TV's for hue & saturation. Something that is not acceptable when
    this "value" amp costs almost as much as a full set of DT40s...

    As this is only my hobby, I haven't had the excitement of buying 100 of these.
    I have worked on a couple dozen, and I only own a few sets, but, I can still
    clearly tell the difference after a couple months of use.

    CT does a good job of shipping them reasonably tuned. The problem is after some
    loving, the scanners aren't factory perfect anymore, and those wee knobs make the
    difference between looking like new and sloppy. For the same level of "easier to tune",
    just apply loctite to the pots you don't want people to twist.

    I'd say the compromise would be acceptable if the 6215s were a lot better and
    you wouldn't miss it, but as is, you can always tell who spent time tuning their
    scanners and who hasn't. And this new lowend amp simply makes sure you
    can never tune it.

    Also, I do understand the reasons why they did it that way, I'm just recommending
    against buying it.

  4. #14
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    PS. I regularly use all the pots when tuning. Following CTI's tuning doc becomes difficult if you don't use them, I
    don't want to need to put the board on a rework station to change these values. HFD and LFD are the least of my
    concern. I'm just at wits end because it feels like every year some useful feature goes away. I don't want a
    Stupidakeyboard(TM)...

  5. #15
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    Hi Adam,

    You raise a few excellent questions. My responses are below.

    But was making them "easier to tune" the ONLY reason the extra controls were removed?
    Essentially yes, but that's a HUGE reason. Ease of use is a hugely important reason to do things. For example, in another forum, Cruch comments on how difficult it is to do a morph with one piece of competitive software, but with Pangolin it's just 3 or 4 mouse clicks… If you are into morphing, then it is clear how ease of use can be an important factor in your buying decision.


    What was sacrificed in terms of adjustability to gain that "major improvement in usability"?
    Well, what was sacrificed was what could be sacrificed, with almost no difference in performance when tuned by experts, and huge INCREASE in performance when tuned by non-experts (and I will remind everyone here that most people are not an expert in servo systems).

    For example, the position scale, position offset and position linearity pots were removed. The 6215 position sensor and mechanical stop system has enough tolerance that, either way, a few degrees bigger or smaller would not make a difference *for most users*. Also, in order to PROPERLY set the position scale in the past, you need a carefully calibrated tangential scale (if you come to Pangolin we will show you ours). Nobody had one of these outside a very few people. Although there are crude ways around this, most of the time this extra pot made for just one more thing to mis-adjust on the part of users. So if you are simplifying things by removing something that *most users* can’t properly set anyway, why not?

    (I will note that although the Position Scale and Position Offset controls were removed, I do believe they retained the overall Input scale and Input Offset, which should suffice *for most users*.)

    For another example, the position linearity pot has also been removed. With the topology of the new position sensor, this was pretty much not needed anyway. Similar to what was described above, to PROPERLY set this pot, you had to have a scope. While some people on PL might have a scope, you wouldn't believe the number of people who contact Pangolin telling me that they did something dumb, such as measuring the color signals with a volt meter... So clearly, not enough people in the world have a scope -- thus, not enough people in the world could properly set this pot to begin with. So again, if you could reduce confusion and get rid of something that people can't adjust in the first place, why not?

    Also, as mentioned before, the high frequency damping was removed, and components were changed to make the low frequency damping control suffice as just "damping". This was done for a few reasons.

    * First, it makes it tremendously easier to tune the servo. In my previous post, I told you that if you double the number of controls, you quadruple the confusion and complexity. But this is not really the case for high frequency damping. It might be more like a cube-law effect. PROPERLY tuning the high frequency damping is actually pretty hard for most people. You wouldn't believe the number of experienced laserists I have seen who did not do this correctly. So by removing this one control, it makes the servo tremendously easier to get right. Also, unlike the dual-damping configuration which had many possible wrong ways to tune, there is only one wrong way (and one right way) to tune a single damping control.

    * Second, the first torsional resonant frequency of a 6215 is nearly 50% higher than that of a 6800 or 6210. That allowed the single damping control to be used. Basically, you don't need two damping controls with the 6215, especially for 30K operation.

    * Third, it is not very well known, but when you use two damping controls, and when you don't have an error integrator (no lightshow servos do), then you actually sacrifice dynamic position accuracy. Targeting absolute positions above a surprisingly low frequency -- around 13Hz -- will take substantially longer to achieve. So in this case, by removing the high frequency damping control, you actually INCREASE dynamic positioning accuracy…

    * And the last reason for getting rid of the high frequency damping control was, for me, a non-reason, but was important to Mike Thanos, who is now Engineering Manager at Cambridge. On a 6800 or 6210 system with high frequency damping, if you grab the mirror with your finger, and GENTLY twist it just a little bit, you will hear the servo "squeak" or "sing". This is because you can't integrate DC -- the current integrator portion of the High Frequency Damping system will become saturated. When that happens, your phase margin is gone, so the servo will become unstable. (Stability returns instantly when you let go of the mirror.) To me it's a non-reason because humans should not be grabbing and twisting the mirror while power is applied... but like I said, it was important to Mike.

    I would say that from an overall standpoint, the 6215 and 673xx amp is the easiest-to-use 30K scanning system for laserists. Aside from the "removed pots for greater ease of use", as I have written in previous posts, the KM (motor constant -- a number which basically indicates how well a motor turns heat into motion) is four times as high as a 6800 or 6210. This means two things. First, it means that the scanner will not get hot (or as hot) as a 6800/6210 with equivalent imagery being projected. This also means that if you want to operate a scanner at maximum temperature, the 6215 can do twice the job (twice the scan angle or twice the speed) when compared with a 6800 or 6210. This is a much more "no nonsense" scanning system for users, and the reasons discussed here, and many others, are why for new users, Pangolin only recommends the Cambridge model 6215 with 673xx or 671xx amps. (Of course, other scanners can be used, but these are the ones we recommend for any new users who do not have legacy reasons for sticking with some other scanner.)


    Do they still sell the old amp design (the one with the extra tuning pots), or is this now the only amp available?
    Well, the 673xx is the model number designation meaning "dual axis amp with normal output configuration". The (xx) at the end would be two numbers, depending on the exact features you need. If you take a close look at the picture posted by Yadda, you will see that there are still places and pads for the "missing" pots. You can purchase a 673xx amp with other configurations, including a configuration with all of the removed pots and even with an integrated notch filter. So yes, this is still available. BUT, what Cambridge considers to be the "lightshow" configuration, is the simplified version shown in the picture. Cambridge tries to keep several of the "lightshow" configuration in stock so if people need them on an quick basis, they can get one or two systems. Cambridge does not stock the other configurations of 673xx.

    And now, a few comments for Yadda.

    Maybe for people like Yadda, who want all of the controls (or maybe more ), you could consult with Cambridge and get the exact configuration of the 673xx you need.


    For a 6215 set for entertainment, you're looking at between $1.2k-$2k depending on quantity and what you want...
    I don't know the normal retail price for a single piece, because we purchase in such high quantity. I will say one thing unequivocally. The price of a 6215 system with 673xx amps, is LOWER than the price of a 6800 system with CB6580 amps. So in other words, Cambridge is giving higher-than-ever performance, for a lower-than-ever price. THIS IS SIGNIFICANT!! And lets look at a few other facts. Before Cambridge came alone, the only other solution was from General Scanning, which was much more expensive and (for most people) gave lower performance. Of course, now we have some bargain-basement alternatives to the Cambridge system, but I don't think anybody here will claim that the bargain-basement systems have the same quality. Maybe that's the difference between my opinion -- as someone who has dealt mostly with laser professionals -- and other opinions here -- which are mostly from the hobbyist perspective.


    As this is only my hobby
    Well, that's exactly my point. For you, this is only a hobby. So you don't have the benefit of the knowledge that can only be gained by seeing how hundreds or thousands of systems perform in the field, nor the benefit of the customer support, seeing how over 7000 people use and abuse systems. As the world leaders in our respective fields (software and scanning), I can only say that we do the things we do for very good reasons!! Sometimes users may not fully understand those reasons, and that's fine. We are always happy to engage in useful discussions.


    Also, I do understand the reasons why they did it that way, I'm just recommending against buying it.
    Well, you are free to make any recommendation you want. And your recommendations can be for your own reasons.

    But from my perspective, given the benefit of all of our knowledge, and the fact that Pangolin has numerous issued and pending patents on scanning technologies, and the fact that we also make scanners for industrial and military applications, we only recommend the Cambridge model 6215 with 673xx or 671xx amp. I hope that for those interested in a truly professional system, they will see the validity of our recommendations.

    Best regards,

    William Benner

    PS: If you liked the pictures seen at the Pangolin Meeting, or on the “Awakenings” show, or of the MTV2 video, these were all done by Hugo Bunk of Laser Image, and he only uses the LD2000 system and Cambridge model 6215 scanners with either 673xx or 671xx amps (depending on the projector configuration)…

  6. #16
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    Laser hobbyist... yes.

    I am not a hobbyist in any other sense technically. This is what the company I work for fields in my day job.


    My company owns the largest surface fleet in the world outside the US Navy. We also run all of the drones for the US and we produce many assemblies for missiles and other projects. This has technical requirements that even the most advanced civilian lasers scanning technologies are nowhere near capable of handling. So please don't dismiss me as unable to grasp the advantages and disadvantages of one or another.

    I do order the scanamps with extra pots... I just got excited by the price difference and ordered that one to evaluate it. And after being initially pleased with them, I realized how much I missed being able to fix the little things. And you haven't addressed my problem, which is that even after modest use, the scanners requires tuning beyond the capabilities of the available pots.

    I would also add that I'm not the only one who uses a scope to tune my scanners. Scopes are cheap and CTI's instructions could be followed by a monkey. I will also claim that there are a lot more experts in servo systems than there are laserists.

    I liked those picture btw. And I agree that you'd get a lot less support calls by removing knobs... And yes, randomly turning knobs can be bad.

    [edit]
    p.s. Before I sound too snarky. Thanks for your posts btw. What you wrote is actually an excellent justification for what happened, and I can see the method behind the madness. I still prefer having more control than less, but it'll be far easier for me to accept that not all people need or want them.

  7. #17
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    Hi Yadda,

    Cool picture. I sure am glad that *somebody* besides the US Government is able to defend us in times of need. God knows the US Government seems to do a horrible job. (As an aside, I sure hope the Secret Service personnel were fired, who were on duty when the Bush daughter got her purse stolen...).


    am not a hobbyist in any other sense technically.
    I know that you are not a hobbyists outside of the laser industry. BUT, within the laser industry I don't believe you have the benefit of knowing how thousands of users (who don't have scopes) can tend to get themselves into trouble. Here at Pangolin, and at Cambridge, it is seen it a lot, that fewer controls = better results by non-technical users. And I don't think it would be very polite to just tell them to buy a scope (and lessons on how to use one)... God, I wish it were that easy... Actually, I wish I had a nickel for every person who told me that they measured color signals with a volt meter...



    This has technical requirements that even the most advanced civilian lasers scanning technologies are nowhere near capable of handling.
    Could be... By the way, if those missiles use thrust vector motors made by MPC, then they may use technology that I worked on...



    And you haven't addressed my problem, which is that even after modest use, the scanners requires tuning beyond the capabilities of the available pots.
    I haven't addressed it because I have not observed this to be the case. Basically, of all of the Cambridge systems we have, we just "set and forget". The Cambridge set of scanners in my personal projector hasn't been touched in years. All of the scanners at Disney's Epcot Center running my servos have not been touched for years. Hugo never messes with the tuning of his scanners... etc...

    The only thing that would require re-tuning is components drifting (doubtful in this design, because of low-drift components that are used) or the KT of the scanner changing. But the KT would only change if the magnet was heated to 110 C or above, and that would only happen if you don't properly heat sink the scanners. Maybe that's what's going on for you?

    And even if this were true, a tweak on servo gain and/or the single damping control should bring them back into tune.



    I will also claim that there are a lot more experts in servo systems than there are laserists.
    Maybe true. The question is, how many servo experts are coincidentally laserists? That's my point!!


    Best regards,

  8. #18
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    well...they are really expensive. Not for my bugdet.
    I may stick to the DT40Pro. But later, I will have the cti scanners...
    My whife will kill me...hehehe

    Thanks for all info ;D

  9. #19
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    William and yadda write so much that I dont think I got time to resopnd on all that and read it all...
    BUT that picture yadda sent was realy cool and it seems like a pretty cool job..

    But the reason that you did post it here was to like say "Hi I got rocket that blow you away if you dont agre with me" ? :twisted: :twisted:



    Cheers Filip

  10. #20
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    Woot! It's almost like realtime chat!

    Thanks, I just wanted to make sure that my opinions weren't being dismissed since I don't pursue this field seriously.
    I'll check to see who makes the motors

    Regarding component drift, I do actually notice some, especially as parts warm up, the components are low TC but
    they don't seem matched. But then again, I may be the only one who noticed and was irritated that you guys
    swapped the 074s on the QM32 for the 084s on the 2ks... But then again I really don't expect loads of stepped
    attenuators in an entertainment scanamp.

    I'm also guilty of having (unreasonable?) expectations of image quality. I often find myself massively irritated when
    watching other people's shows and see non-perfect tuning That's actually how I met a few local laserists. I ran up
    after the show with a set of scopes (I keep a portable Tek in the trunk) and offered to retune their scanheads for them.
    I'm quite sure everybody knows how to do it, but most people do like to set and forget.

    [edit]

    ps. Hehe liteglow... it was the first pic I could find from the releases that wasn't the boring inside of an office building

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