Topic: Howto: simple Differential Amp + TTL ?

[Xer0]

First of all, do you get mesurable signals, when you play wave, from the output of the sound card itself?

You should be able to read it with your meter set to AC volts.
The silent DC offset on the DAC is zero volts AC.
The colors should show a big change on your DC meter when you play and stop the wave.
If you can measure the silent DC offset on all channels

Yes

yes
yes
yes
yes


I suspect it has something to do with the DB25 connection. i think i must reverse all pins from right to left on the plug when i want to use the Projector's ILDA Out port to feed signals in, otherwise im sending "Shutter" to "X+" and "X-" to "GND" like it seems.

[meandean]

I suspect it has something to do with the DB25 connection. i think i must reverse all pins from right to left on the plug when i want to use the Projector's ILDA Out port to feed signals in, otherwise im sending "Shutter" to "X+" and "X-" to "GND" like it seems.

  The old mirror-image trick!

[James]

There are tiny numbers molded into the plastic pin spacers.

I always look before I solder.... I always get whacked-out with the front / back, male / female stuff.

Red striped ribbon into DB25 is kinda' neat. You just need to lay down a whole set of 26 pin headers on your board.

James. 

PS.

"I always get whacked-out with the front / back, male / female stuff."

Nothin' like leavin' a loaded gun laying sround. 

[Xer0]

Red striped ribbon into DB25 is kinda' neat. You just need to lay down a whole set of 26 pin headers on your board.

Yeah i have one ot these flatcable plugs... just stick in and press, easygo!
But it was a DB25 male plug and the ILDA standard needs female
So i need new plug + cable or an gender converter. bought a solderable f plug today and will try with this. my first idea was just use the ILDA IN Port of the Projector. but it seems i have to mirror-switch all pin positions first!

PS.

"I always get whacked-out with the front / back, male / female stuff."

[Xer0]

Ay dammnit. i switched all the cables and now the PF is doing nothing.

Is it not possible to feed the ILDA signal into the "Out" Port of a Laser Projector instad using the "In" Port? at first pinout it at least produced a standing beam...

[James]

Is it not possible to feed the ILDA signal into the "Out" Port of a Laser Projector instad using the "In" Port?

That's what a meter is for!

Check continuity between each position on the mail and the female connector.

James. 

[meandean]

 OK Jimmy, now you're ranting...

 This is a long shot, but if you're using test signals like max.wav or circle, these signals are inverted because many of the correction
amps out there are inverters (I may be the guy to blame for that).

 You have a 25pin connector and a breadboard... I suggest you use the 'in' socket on the projector, and take it a step at a time instead of just plugging the whole thing in and expecting it to work- get your meter out and VERIFY each pin, starting with the interlock and  shutter circuits, apply +5v to one color channel to see if you get a parked beam of the expected color and move on from there.

 As James would say: "You have the rest of your life to learn electronics".

[James]

The best thing about an single stage, inverting op-amp is that a veriable resister in the negative feedback loop will allow you to turn the gain down to ZERO.

With a non-inverter, you can only turn it down to 1 times the input voltage.

James. 

[Xer0]

Check continuity between each position on the mail and the female connector.

The pins on OUT are eactly mirrored to the ones on IN. X,Y,I,R,G,B & GND are connected the others not. I- is connected to each R,G,B + ... strange.
Anyway it should work then with my reversed plug but it doesnt. and i want to lase now not wait until the order with the correct plug will arrive

[James]

So why don't you just temporarily wire it together with no connectors?

James. 

[Xer0]

How? In my Breadboard they are temporarly, i just soldered pins to the 25 wires of a flat cable. bu to connect it to the Laser i need a DB25 female. and i bought male, so i tried to feed it through the "Out" port, while i ordered the right plug and waiting for it

[Xer0]

Aww... still in Memphis. (nah, not really there, but still not delivered to my house ^^)

But in the spare time i redesigned the Vref Circuit and using teh 10k Poti which have been unsed for LM336 fine adjustment now instead in the inverting buffer to make precise -2.23V from a stable +2,49V ref. Yes my SoundCard has 2.22-2.24V offest. lol

[James]

How?

You can get to all the wires inside the projector, correct?

Just tap into it!

James. 

[Xer0]

You can get to all the wires inside the projector, correct?

Noo... i didn't opened it yet. want to keep it sellable after im bored by it, so have a bit fear of fizzling into it. anyway i would need some kind of 25pin rm 1,25 connector, thats what the board inside is connected on. now i have my db25 female plug - but still it dont works like it is supposed too!

[Xer0]

Boah i am noob -.-

Played always max.wav and assumed it makes a circle, than wondered why the output dont changes/laser dot is beyond output window.

Now with HE is finally does scanning! but i have to build the color stage too, no blanking