ADAT mods +/-5v instead of 10v

So, quick introduction, I have been out of the laser bit for 10 years or so. I used to run completely live and saved imagery shows (I controlled color/modulation, effects, etc). I ran across a friend with a sweet laser pointer, and it started my interest again. I am part way through building my own rgb projector. 2.5W or so mostly from memory. I have gotten everything down so far, save one item, and that's why after about 4 months of looking around on here I finally signed up.

Hopefully someone can point me In the correct direction, yes I have searched.... for hours... And cannot find my answer. So here goes:

I am modifying a blackface adat for ilda output using the pango guide and this thread https://www.photonlexicon.com/forums...Expanded/page2
But I cannot figure out how to properly limit the output of the x-y channels to +/- 5v. I am going to be using pt-30k scanners from spacelas and their limited documentation says +/- 5v input. Any help would be greatly appreciated.

I have a donor elco cable so I can use the connector and the 1/4 connectors as needed to make whatever whatever outputs I need for the projector.

Not sure this the way but how about a pot. Line level translate opamp. Pot with zener for protection opamp buffer. Rail to rail opamp run at 5v. Will just clip. Pot seems easiest ....play a full scale signal and set the pot.

Ps. DZ sells an adat lightpipe to ilda converter. You do know most people dumped adat and playback via DAC these days.

Yes I know most have dumped adat. But I am a electronics guy, and I have an Alesis blackface sitting around, more of a I know I can make this work kinda thing

And I happen to have a copy of digisynth I want to play with

Matt’s one of my best friends and neighbors..... I use a transcoder.

I don't remember if it was him that came out to help us get setup but I worked for Karl at the laserdome in pa for a number of years. I want to say he came out in the summer of 06 to help us get our new system up.

I can't even find the transcoders, and I think that's a bit out of my price range even if I could find them.

The adat worked for us there and I have one. I'm just trying to figure out what resistance to use on the tl084 to drop the differential output to -/+ 5v. I think i can use drlavas guide for the + side of the opamp. That gives 5v but I am unsure for the - side opamp resistance change.

Actually I think it might have been chuck that came out to help us. Long time ago, can't really remember

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Originally Posted by Theoneinformant

Actually I think it might have been chuck that came out to help us. Long time ago, can't really remember

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I think iknow who you you are then. That was a while back. He moved so I have not seen him for a few years. I remember 29 palms.

I worked there during highschool up until I joined the Marine Corps. It's been a while haha

Surprised I don’t know you. Maybe I do? Did you have a bird by chance

A bird? Not sure what you mean. I had a pair of cockatiels for awhile? But very few people knew that.

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Originally Posted by Theoneinformant

But I cannot figure out how to properly limit the output of the x-y channels to +/- 5v.

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The output from the blackface is 0-10 volts single-ended, right? In that case you need to build a differential receiver with gain adjustment and zeiners on the outputs to prevent over-volting. I've got a schematic at home I can post later tonight. Or am I missing something here?

Adam

Output from a blackface is 10v diff

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Originally Posted by Theoneinformant

Output from a blackface is 10v diff

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Got it.

OK, this circuit will work with a slight modification. You'll need to change the feedback resistor on the first op-amp from 10K to 5K. (Feedback resistor connects the output of the op amp to the inverting input. It's the vertically-oriented resistor below the first op amp.) That will cut the gain of the receiver stage in half. From there on everything should work correctly.

Attachment 53814

If you don't change that first feedback resistor the output of the receiver stage will clip when it reaches the max input voltage. You *could* run this circuit as drawn if you go up on the power supply voltage to the op amps (something like +/- 24 volts ought to do it), but then you'd have to dial the size pot way down to prevent the zeiners on the output stage from clipping the image.

Adam

Good idea, but I am trying to figure out what resistor value to change in the op amp inside of the adat. I have the value for the + side. Haven't worked out the - side yet. Got stuck on other parts of the project, moved the whole projector onto a different breadboard, and I'm working on a high power long distance corrected nubm44 diode build. Long distance = 32000 feet, or 7.25 miles. Divergence is down to the point I'm having a hard time measuring it over 100yds.... Once I have that one worked out in going to pbs it with a second nubm44...

You might look at the drv134 series of drivers send the signal down the line differential. You can then increase the voltage of the signal to compensate for the line loss. 7 miles of copper is a crazy cost. Can you do an rf solution or even an optical solution if line of sight?

I'm trying to get the diode to be a visible spot at 7 miles. The nubm44 diode is a 7w capable diode, not send the signals that far.

GO LED. You get much better power and the divergence is actually good unless you want super secret communication. In the case encode the transmission. There is a study regarding the mode hoping of laser vs led and led wins. You use a fresnel lens system. 7 miles is really simple. The ones i was looking at were doing 62miles.

http://www.lightwaveonline.com/artic...-53449272.html
http://modulatedlight.org/optical_co...cal_index.html


as an example. Matt was actually the one that pointed me to led when I tried what you are doing.

I'm looking for spot on target, it's not for communication.

Beam expander. Good luck aiming and when the air between changes it will drift. You need to figure the link turbulence possible and double the size of the resulting target. This way the target stays in the zone of illumination even if the air moves. As the one article said, mode hoping with multimode laser diodes add a severe amount of noise to the signal. LEDS don't have that because it is smeared over the entire cone of illumination. Thus the only selective lensing that occurs is from air turbulence which is not trivial. (it is possible to have no signal at all on the detector as the lens effect moved the power to a section of the cone not illuminating the detector. If you refocus the beam on a small detector via Fresnel of as you wish...it essentially reintegrates the noise in the cone because it is made smaller than the detector surface again. LEDS are more homogeneous but still can be lensed in the same way just the noise in the beam is less to start. Just a summary of the second link as I understood it.

I'm in the desert so at night I think it should be pretty stable temps, less turbulence, and yes on the beam expander. Just finalizing the focusing adjustments.

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I have a small manual mill, so most of these one off parts takes a while.