Wobbly image

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12-10-2008, 07:05
FourDee

Wobbly image

Hi,

as some of you may have read in a post I made a couple of days ago, I just finished my projector.
I'm very happy with it overall, but there are a few things that still bother me.

I'm using an FB3 together with DT40pro's. I have incorporated the FB3 into my projector housing. The signal ground of the DT's is not connectd.

When I project an image that is not moving, I notice the image is a bit 'wobbly'. Its not a wobble in the lines, but the entire image seems to be moving a little.

Does anybody have a clue what could be the cause of this? How can I fix it?
12-10-2008, 07:34
drlava

That's powerline hum interference, most likely from improper signal grounding.
12-10-2008, 08:26
FourDee

But I thought I wasn't supposed to connect signal ground ...
12-10-2008, 08:44
andy_con

sounds like my issue which bill sorted.

do you have the big pot attached?
12-10-2008, 09:01
FourDee

The size pot? I haven't used that one.
12-10-2008, 09:14
andy_con

problem

http://i80.photobucket.com/albums/j1...832Large-1.jpg

im trying to find a pic of the pot
12-10-2008, 09:36
FourDee

Like I said in my first post, it's not the lines that are wobbly, but it's the entire image that shakes a little.
But thanks for thinking along anyway
12-10-2008, 09:45
tocket

Check if you have a loose connection somewhere. Mine does that when the ILDA-connector is loosely attached.
12-10-2008, 10:00
Stuka

I've also seen that when one of the leads between a scanner and scanner amp wasn't firmly attached...
12-10-2008, 10:32
DZ

Does the FB3 output to a DB-25? Connect pin 25 from the FB3 to "common" on the power supply for the scanners.
12-10-2008, 10:43
James Lehman

Check it out!

http://www.akrobiz.com/laserboy/graphics/laser_m_53.jpg

This is what my CT scanners looked like before I figured out that I had the scanners and the amps switched. IOW, the X amp was driving the Y scanner and vice-versa.

James. :)
12-10-2008, 10:58
FourDee

Quote:

Originally Posted by DZ

Does the FB3 output to a DB-25? Connect pin 25 from the FB3 to "common" on the power supply for the scanners.

That's something I thought of doing also.
I'll try it when it get back home to my projector this weekend.
12-10-2008, 11:16
allthatwhichis

Quote:

Originally Posted by DZ

Does the FB3 output to a DB-25? Connect pin 25 from the FB3 to "common" on the power supply for the scanners.

Bingo... :cool:
12-10-2008, 11:58
FourDee

I purpously didn't connect the signal ground to pin 25 because the writeup of Bill Benner about projector wiring mentioned not to do so ...

But I didn't have too much time sunday and i didn't try it out :) I'll try it on friday
12-10-2008, 12:01
allthatwhichis

I tried that also and had a nasty wobble... pin25 to scanner common on PSU, wobble gone. :confused:
12-10-2008, 12:09
DZ

Quote:

Originally Posted by FourDee

I purpously didn't connect the signal ground to pin 25 because the writeup of Bill Benner about projector wiring mentioned not to do so ...

But I didn't have too much time sunday and i didn't try it out :) I'll try it on friday

Well knowing that it isn't connected means this is definately, 100% the problem. The amps need some kind of reference, the differential signal alone isn't enough. If you re-read through Bill's recommendations, it should say somewhere in there about connecting ILDA pin 25 to the scanner power supply by way of "star grounding". Now, depending on how your projector is wired, this may not mean you simply connect it to "FG" or "GND". Which is typically "earth ground", you instead may want to connect it to the 0V line from the power supply, or "common".
12-10-2008, 12:13
FourDee

Aaah, maybe if I join the grounds of the 24V psu for the scanners and the ground on the 5V psu I use to power all the rest (including the FB3) :)

But anyways, Isn't it the poin of differential receivers that they don't need a reference? Just a voltage between the two terminals ...
12-10-2008, 12:19
colouredmirrorball

FourDee, or Niels if I remember right:
where are you in Belgium? I would like to see a real RGB (if it is not too far) as an example for my own one (currently just a broken computer case on the attic :o)
And don't forget to take pictures sunday!
12-10-2008, 12:36
FourDee

I'm in Menen, that's pretty close to where you live if I'm not mistaking.
I'm sure we can arrange to meet sometime (but first I need to address some issues (like the grounding problems))

I'll let you know ;)
12-11-2008, 01:10
colouredmirrorball

That would be great! Maybe in a school holiday, for example the next one (first have to take a few more exams... only four... must... resist... urge... to... fall... asleep... must... study... only... four... left... almost... holiday...
Sorry, I must have felt asleep in the past sentence :rolleyes:)
From what I understood in your posts you're also a student, because you were not home during the week?

Where do you live in Menen? I can take a train to there, if it isn't too far away from the station.
Oh well, I will send you a PM with all details, when I have convinced my parents ;)
12-15-2008, 05:52
FourDee

This problem was solved this weekend by connecting signal ground to pin25.

I tried to tune the scanners this weekend using buffo's tutorial. It worked pretty well, but i do notice something in the lasermedia test pattern. The lines do not separate in the diagonal parts, indicating that both scanners are running at the same speed. But instead, the diagonal lines don't join in a point in the center of the sides of the big square. They draw away, making kind of a bend into the sides

Is this because I'm scanning at too big of an angle?
12-15-2008, 08:57
buffo

Quote:

Originally Posted by FourDee

Is this because I'm scanning at too big of an angle?

Possibly. What does the standard ILDA test pattern look like? Can you post pictures of both patterns? Also, what scan angle are you running?

Adam
12-15-2008, 09:04
allthatwhichis

Quote:

Originally Posted by FourDee

This problem was solved this weekend by connecting signal ground to pin25.

I tried to tune the scanners this weekend using buffo's tutorial. It worked pretty well, but i do notice something in the lasermedia test pattern. The lines do not separate in the diagonal parts, indicating that both scanners are running at the same speed. But instead, the diagonal lines don't join in a point in the center of the sides of the big square. They draw away, making kind of a bend into the sides

Is this because I'm scanning at too big of an angle?

Nice! Always like to hear a solution owrked. :D

As for the test pattern... Mmmmm pictures... ;)
12-15-2008, 09:47
FourDee

I figured you would say that :)
I dont have acces to the laser during the week so ...
12-15-2008, 10:02
allthatwhichis

You poor soul!

:eek: WHAT? I'd die... or go blind... of... photon thirst. :eek: You at least have a pointer to carry around right? :confused:
12-15-2008, 10:39
FourDee

no sir, I just have some beam shots I made during the weekend to get trough the week :'(
12-15-2008, 11:04
allthatwhichis

I need an hour or two of personal coherent photon time every day. ;) I could take a day or two off, but would need to take a higher dosage to catch back up... >:) I don't go outside in the sun light though; it is a trade off in radiation. :rolleyes: