FB3 hookup - help!!!

[Pangolin]

... therefore, I suggest to connect the amps ground

Ummm. aha. And, for the record, may we all know who "I" is? Could you please state, for the benefit of the members here on PL, your credentials, including any degrees you hold, any patents you hold, and any accolades you have won as a testamente of your own ability to make such a recommendation?

recommends to connect the ground for Analog Differential Input Configuration, according to passage (below) of the manual of Micromax 671 Series, pag.46

It's easy to fall into a trap and take things out of context.

With respect to why Cambridge makes the recommendation they do in their manual, and why there are three connections on a scanner amp -- if you have only a single scanner amp, then you might get away by connecting your "signal ground" to the scanner amp's ground. But for everyone here doing two-axis laser graphics and beam shows, you have two amps, not just one, and connecting your "signal ground" to the ground connection of both scanner amps will cause this kind of "ground loop" (I hate that term because it is way over used), and the X amp will experience "ground bounce" when the Y amp undergoes hard acceleration, and vice-versa. The result is crappy images (to some extent), the extent depends on the gauge of the wire, the degree of acceleration, and other factors. You can avoid all of this by making only one single ground connection *somewhere*, and the best place to do that is the common ground connection at the power supply itself.

For the record, I have nothing to prove. If you want to follow my recommendations, it doesn't make me feel any better about myself. And if you don't take my recommendations, it won't make me feel any worst about myself. I am confident in who I am as a person, and confident in my abilities as an engineer. Likewise, there are those who have known me for a very long time and, lets just say my reputation preceds me. For those who don't know me, I have the technical certifications, patents, awards, and other accolades (letters of commendation from heads of state) to prove that, by and large, I know what I am talking about.

Of course, I can always make mistakes (more about this in another post). I myself have made the very same recommendation that Cambridge made years ago (thanks for pointing this out DZ -- I will change my own docs). Today I count those older recommendations as a mistake, and my latest recommendation is to connect the DB25 to the ground of the power supply and NOT directly to the amps. I have my reasons, and in the lab, I can show you or anyone else the difference.

Bottom line -- people (and companies -- BIG ONES) send me scanners to improve. The people here on PL can universally tell you that when they get back their scanners from me, they are wired the way I am saying in these recent posts. And wiring these scanners is the very LAST thing that I do -- so the wiring is not done out of prejudice, or wanting to prove that I am right. The fact is, these systems don't look as good as they do, unless they are wired the way I say. And those are the facts.

In any event, anybody here is free to choose whatever wiring method they want. On a personal level, I don't care. You aren't going to hurt my feelings if you don't follow my recommendations, and aren't going to stroke my ego if you do. Aside from just wanting every laser show to appear as good as it can (for reasons stated in other posts), I really don't care. Especially if you are a competitor!! Definitely don't follow my recommendations !!!

On a hobbyist level, maybe we can just change the statement a bit. The wiring I suggest is "what works for me". I believe it will also work for everyone else, and recently, big projector manufacturers have changed their designs, so they believe me too. You can try it, and see if it works for you too. If it does, then great. If it doesn't, then figure it out for yourself. Really that's the spirit here on PL -- figuring things out for yourself (hopefully, with the help of others), and then sharing your experiences.

As a final note, can I call on some of those for whom I have tuned (and changed the wiring on) their scanners, to post in this forum about what your scanners looked like before, and after they visited Pangolin? Sure, there are many changes done, but the wiring is one of the changes that leads to the pretty pictures .

Best regards,

William Benner

[carmangary]

OK, I think it is time for a WIRE OFF!! OK gents, display a pic with wiring one way and snap a photo. Change your wiring and snap another. It's time to put the copper where the mouth is.

Actually, as silly as it sounds, I think it is actually a good test to see the differences. But, of course I don't really expect anyone to do this since it would be a bit of a pain in the neck to do.

[mliptack]

Gary - If you want to see the huge renovation I have made check out this thread...

http://www.photonlexicon.com/forums/...nning+building

That thread takes me from knowing very little about Laser Projectors to where I am currently standing with my projector as of about yesterday

I am so happy with my current set up I fired it up first thing this morning along with the fogger and got ready for work with the diffraction grating lighting up the room

[Lasershow]

Bill in first point, I want to leave a very clear thing that I am not challenging you, because for the way that you wrote, it seems that you were offended with my placement, I only put in the post the opinion of Cambridge that in the moment I share, but that can be changed, reminding you that the basic purpose of the PL forum is exactly to try to explain doubts and/or to solve problems remotely, in other words, at the distance and to change ideas to learn several subjects, besides the technical discussions, I don't want to discuss and to "fight" with you, I only want to change ideas and knowledge, OK?

Ummm. aha. And, for the record, may we all know who "I" is? Could you please state, for the benefit of the members here on PL, your credentials, including any degrees you hold, any patents you hold, and any accolades you have won as a testamente of your own ability to make such a recommendation?

I am an Engineer formed in 1984 and I work with Laser Light Shows about 25 years and therefore I have a lot of experiences in field and I think there is no need to tell my credentials in full detail, unless you want to know particularly, because this is not the purpose of the forum and the recommendation that I did is orientation of Cambridge Technology, see attached files

With respect to why Cambridge makes the recommendation they do in their manual, and why there are three connections on a scanner amp -- if you have only a single scanner amp, then you might get away by connecting your "signal ground" to the scanner amp's ground. But for everyone here doing two-axis laser graphics and beam shows, you have two amps, not just one, and connecting your "signal ground" to the ground connection of both scanner amps will cause this kind of "ground loop" (I hate that term because it is way over used), and the X amp will experience "ground bounce" when the Y amp undergoes hard acceleration, and vice-versa. The result is crappy images (to some extent), the extent depends on the gauge of the wire, the degree of acceleration, and other factors. You can avoid all of this by making only one single ground connection *somewhere*, and the best place to do that is the common ground connection at the power supply itself.

The recommendation of Cambridge is for Dual Axis System with Analog Differential Input (+ input, - input and GND) and that there should be the direct ground connection from the signal source to the Pin 2 on the input connector (J1, Pin2 - ground) on the shield of the wire or the separate wire. If shield wire is not available, use a third wire then twist all wires to provide some level of shielding and still connecting wire ground between specific points of the boards, to avoid strong coupling between channels and also to reduce crostalk between the two channels caused by high ground currents (power connections), you see attached files ElectricalDetails.jpg in the bottom of the item 7.3 Command Input Wiring and also in SignalConnectionsDiagram.pdf

For the record, I have nothing to prove. If you want to follow my recommendations, it doesn't make me feel any better about myself. And if you don't take my recommendations, it won't make me feel any worst about myself.

I don't want you to prove anything and nor that the your recommendation makes you to feel better or worst about yourself, I only want that technically, be discussed by several members this subject, to obtain a conclusion.

I am confident in who I am as a person, and confident in my abilities as an engineer. Likewise, there are those who have known me for a very long time and, lets just say my reputation preceds me. For those who don't know me, I have the technical certifications, patents, awards, and other accolades (letters of commendation from heads of state) to prove that, by and large, I know what I am talking about.

I am not doubting of your abilities, reputation and nor than you are talking and I don't want to say anything, that it changes your opinion and once again I only want to discuss the subject technically.

Of course, I can always make mistakes..... I have my reasons, and in the lab, I can show you or anyone else the difference.

All of us makes mistakes, we are not still perfect and Ok, I going to USA, I will inform you for you to show me the difference

In any event, anybody here is free to choose whatever wiring method they want. On a personal level, I don't care. You aren't going to hurt my feelings if you don't follow my recommendations, and aren't going to stroke my ego if you do. Aside from just wanting every laser show to appear as good as it can (for reasons stated in other posts), I really don't care. Especially if you are a competitor!! Definitely don't follow my recommendations !!!

Each person can choose what to think better for itself and I don't want to hurt your feelings or to stroke your ego with relationship on to follow your recommendations, what I want is to discuss this subject technically and I don't feel your competitor and yes your partner of PL forum and who knows a future customer.......

On a hobbyist level, maybe we can just change the statement a bit. The wiring I suggest is "what works for me". I believe it will also work for everyone else, and recently, big projector manufacturers have changed their designs, so they believe me too. You can try it, and see if it works for you too. If it does, then great. If it doesn't, then figure it out for yourself. Really that's the spirit here on PL -- figuring things out for yourself (hopefully, with the help of others), and then sharing your experiences.

I think should not have differences and to change the statement a bit on a hobbilist or professional level, because the technical information has to be same for everyone.
I can try and to verify if it works for me and to talk for you the result, but could you send me a Wiring Diagram for my scanners and servo boards?
I also think the spirit here of the PL forum is to help the other members and to share our experiences.

As a final note, can I call on some of those for whom I have tuned (and changed the wiring on) their scanners, to post in this forum about what your scanners looked like before, and after they visited Pangolin? Sure, there are many changes done, but the wiring is one of the changes that leads to the pretty pictures .

Ok, I would like you to call then some members that changed their wiring for them to talk their experiences and to share with the other members here of the PL forum

Best Regards

Carlos

[buffo]

I agree that we don't want a flame war! But I do think that this is an interesting topic, and I would like to hear more on the subject.

I spoke with Bill Benner about this issue last week on the phone. Based on our conversation, I decided to perform some tests on my projector.

I have a Pangolin QM-2000 intro board connected to my home-made RGB projector. The scanners are DT-40 pro's from Jian. They are powered by a pair of 24 volt power supplies in parallel. The + terminal of one PSU is connected to the - terminal of the other PSU, giving me a +24 volt rail, an isolated ground rail, and a -24 volt rail. The power supplies are each rated for 5.5 amps continuous output, which is more than double the current that the standard DT-40 scanner power supply can deliver.

I have pin 25 on the ilda connector wired to the ground input on the scanners. This is also connected to the negative blanking leads on all lasers in the projector. However, it is *not* conencted to the ground on the power supply feeding the scanners.

Of course I have X+ wired to the X+ input ont he amp, and X- connected to the X- input, and the same thing for the Y amp.

Last night I disconencted the ground wire going to the scanner input. I did not see any change in the scanned image. I loaded up the quadrature square wave pattern and collapsed the Y axis to zero percent size. Then I looked along the now-horizontal line that was being scanned and watched for any signs of movement in the Y axis. I found none.

Then I reverse the settings so the X was collapsed and Y was at 100%. Again I looked for any movement in the X axis, and again, I found none.

Finally, I re-connected the ground wire to the input to the scanner amps and ran both tests again. I still did not see any sign of noise.

In the next day or two, I plan to conenct a ground wire from the scanner amp PSU ground to pin 25 and then repeat these tests again. I'll try to post some pictures as well.

Adam

[carmangary]

I am guessing that probably still had between the two. Could you check with an ohmmeter to see if there are any noticeable changes in resistance?

[buffo]

Good idea, Gary. I'll check the ground potential on that scanner amp PSU (with the pin-25 connection to the signal input lifted) the next time I power up the scanner, and I'll post my results here.

Adam

[Lasershow]

I have a Pangolin QM-2000 intro board connected to my home-made RGB projector. The scanners are DT-40 pro's from Jian. They are powered by a pair of 24 volt power supplies in parallel. The + terminal of one PSU is connected to the - terminal of the other PSU, giving me a +24 volt rail, an isolated ground rail, and a -24 volt rail. The power supplies are each rated for 5.5 amps continuous output, which is more than double the current that the standard DT-40 scanner power supply can deliver.

I have pin 25 on the ilda connector wired to the ground input on the scanners. This is also connected to the negative blanking leads on all lasers in the projector. However, it is *not* conencted to the ground on the power supply feeding the scanners.

Of course I have X+ wired to the X+ input ont he amp, and X- connected to the X- input, and the same thing for the Y amp.

Last night I disconencted the ground wire going to the scanner input. I did not see any change in the scanned image. I loaded up the quadrature square wave pattern and collapsed the Y axis to zero percent size. Then I looked along the now-horizontal line that was being scanned and watched for any signs of movement in the Y axis. I found none.

Then I reverse the settings so the X was collapsed and Y was at 100%. Again I looked for any movement in the X axis, and again, I found none.

Finally, I re-connected the ground wire to the input to the scanner amps and ran both tests again. I still did not see any sign of noise.

In the next day or two, I plan to conenct a ground wire from the scanner amp PSU ground to pin 25 and then repeat these tests again. I'll try to post some pictures as well.

Ok, Adam thank you for the confirmation, because each installation will have an performance different, due to the scanner type, servo driver and power supply of the wiring with DB25 ILDA'S ground (Pin 25) connected for Scanner Amps's ground, as I informed in the previous post, therefore it is necessary to test for each installation particularly and to verify the results, to decide if the ground will be tied or not.
This is also my recommendation, shared with to Cambridge, until that somebody proves me differently.

Thanks

Carlos

[buffo]

Ok - I did some more tests. Unfortunately, the results aren't very conclusive...

First, Gary - I checked to see if there was any potential difference between the isolated ground of the Scanner amp PSU and earth ground. There was no difference.

However, as Bill mentioned earlier, since just about every device in the projector is grounded to it's case, which is bolted to the optical table, which is already at ground potential, I suppose it's not surprising that I didn't get any reading other than zero. (I didn't disconnect the scanner amps from the PSU, so my guess is that they were grounded through the scanners to the optical plate.)

Just for grins, I connected a ground wire from pin 25 to the ground on the scanner amp power supply. Then I removed the ground from the scanner input. No change in scanned images. (I looked at the test pattern, as well as the quadrature square wave pattern with first the X axis collapsed, and then the Y axis collapsed.)

Then I connected pin 25 back to the input connector on the scanner amp, and left the other ground wire from pin 25 connected to the power supply. Still no change.

Finally, I removed the ground wire going to the scanner amp power supply and left pin 25 connected to the scanner amp input. Still no change.

I should note that in my projector, the red, green and blue modulation signals are connected with the positive leads going to the R+, G+ and B+ pins, and the negative leads are connected to pin 25.

If I get *really* ambitious, I might yank those negative leads loose from pin 25 and connect them to the R-, G-, and B- pins, just to see if it makes any difference. But I don't see that happening any time soon. (I've got another big project in the works at the moment, and I still haven't done my taxes yet!)

Adam

[carmangary]

I am willing to bet that the - RGB pins on your DAC are tied to ground so it won't make a difference which ones you use. But, it would be a good idea to connect then to the - RGB pins in case you happen to switch DACs sometime in the future and it doesn't have them tied to ground.