Topic: Howto: simple Differential Amp + TTL ?

[James]

That projector is TTL on all the colors, you know.

Why don't you just use LaserBoy to make shows? That's what it was written to do. Plus the sound card DAC was designed for LaserBoy waves.

You can easily make a palette of only 7 colors and get the most out of what you have.

James.   

[Xer0]

I didn't got "into" Laserboy yet. HE is a Point&Click App ideal for Windows Users like me xD so i used this to make the test runs. Yeah Blanking is strange yet. have to connect one of the colors to -5V and the others to SC out. then one color is blanked and the other stays. So in need to build an single ended RGBI amp stage on my breadboard too. Or is there a way to make the Soundcard output a DC voltage higher then 2.5V ? (TTL)

[James]

If you had just made all of the correction amp channels the same (single ended) you would be able to do all sorts of things with LaserBoy. You can invert any one of the channels in software and leave the others as-is. You can also open the wave in Audacity and do stuff. O-scopes have an input to control the brightness of the trace and it goes from -5V (off) to zero V (full on). LaserBoy has an option to put a mono signal like that into the last track of the wave.

You should at least try LaserBoy. It's not THAT complicated. 

Where did you get circle.wav ?

James. 

[Xer0]

Where did you get circle.wav ?

I dont have circle.wav. I red about it somewhere but cant find it nowhere anymore. My thougt was that max.wav is a circle so thats why the whole setup semmed not beeing working for me...

[James]

You can't find it because it's in the LaserBoy application!

Frame 10 is a big white circle.

Output that as a still frame wave for 10 seconds (default settings).

Call it circle.wav.

Ta-Dah!

It would be rediculous to distribute the wave over TCP/IP.

James. 

[Xer0]

RAR'd Waves are very small... or why not FLAC?

[James]

y 10 [Enter] o 3 2 circle [Enter]

Look in ./LaserBoy/wav/

That's about as compressed as it will ever get.

the file in.ild has quite a few unique frames that are there to demonstrate all sorts of neat effects you can do with LaserBoy.

James. 

[Xer0]

OK... almost anything allright now. I used a TL074 for the color channels, Amp to max 4V

But still some very strange issues:
1. Had to change color chan assigment for correct output. on some frames still wrong
2. the picture sometimes "hops" barely noticable down and up again. On some of the Test Frames in HE Laserscan, the otherwise blanked colors in this moment apear again.

[James]

One of the nice things about using wave is that you can open it in almost any application written to view or edit wave.

You can clearly SEE what you have as data for a starting point.

With that, a meter and a bit of thought, you can definitely indentify your problems and fix them.

James. 

[Xer0]

Do you think it could be cause i dont use any caps on outputs?
I only have some electrolytic Caps between +5V/GND, -5V/GND and +5V/-5V
Where i should plase the bunch of tantalum 100pF caps i bought?

[meandean]

Do you think it could be cause i dont use any caps on outputs?
I only have some electrolytic Caps between +5V/GND, -5V/GND and +5V/-5V
Where i should plase the bunch of tantalum 100pF caps i bought?
 
 

 I don't think 100pF caps would do anything... I would like to know more about
the circuit you are using for the color channels...

[Xer0]

It's the one James uses for all his channels.
Just that i took a TL074 quadopamp, 8x 10k resistor for signal + vref in, and 4x 50k pot for gain adjustment. these are 1-turn trimmers so not really precise, but its TTL anyway.

Vref is adjusted via an inverting gain<1 amplifier, from LM336's 2,49V to globally -2,23V

[meandean]

 Try rendering some waves in LaserBoy and see what you get.

[Xer0]

Boys.. .very important question:

When i use single ended for colors, wiht inverting amps... on the breadboard i had the ilda colors + pins connected to amplifier's output and the - ones to gnd. Can i switch this, so going with - to opa's out and + to gnd, then set "invert on" in the ezauddac driver? can this work with laserboy too? it would simplify my soldered board design!

[James]

All of this was figured out for you.

Try it THAT way once.

James.