You people want to say that my correction board is not correct?
Do anyone have schematics of correction board that works?
Junior Member
You people want to say that my correction board is not correct?
Do anyone have schematics of correction board that works?
Senior Member
Please take another look at post #14 in this thread, it contains a link to the correction amp schematic that you need.
Most soundcards like the CM106 are unable to generate negative signals. The CM106 outputs about +2.25v when no digital signal is applied, and the output can swing about +/- 1.5v from that value when signal is applied, for a total range of +0.75v to +3.75v. This signal goes through a DC blocking capacitor to the output jacks and you get AC for audio. You need DC for the laser so you must get your signal before the capacitor, and you need a way to subtract the 2.25 idle voltage so that the output is 0 with no signal applied.
The correction amp is a summing amp; it adds the positive soundcard ouput to an adjustable negative voltage so that the final output is 0 when no signal is applied, and it can produce DC in either direction with adjustable gain. Your diode driver circuit alone does not have the range of adjustment that you need. Try placing a correction amp stage before it. The correction amp is also designed to drive the scanners directly.
Dean
Junior Member
OK, I see now.
Do I have to remove everything before "analog driver part" and connect it to new opamp correction board that drlava posted?
But can anyone see what is the problem in my schematic?
Maybe I can solve problem if I just connect opamp output to non-inverting pin of CA3140 and not connecting it to inverting pin...not?
Senior Member
From your print, the opamp output is already connected to the non-inverting pin.Originally Posted by ReNNo
The CA3140 stage is a voltage to current converter, and it only works in one direction.
Diodes (including lasers) are driven by current in one direction, not voltage.
Dean
Last edited by dchammonds; 10-14-2010 at 19:05.
Senior Member
If this is the case, then you should adjust it to get -5V when max.wav is playing and 0V when it is not. Then use the invert option in EzAudDac.ini for that channel and double check that it is now 5V when playing and 0V when not playing.
Junior Member
No drlava, I'm not talking about galvos opamps, I have problem with laser drivers.
Opamps for laser drivers give only positive or only negative voltage, cannot achieve +-5V. (I can do that with galvos opamps)
And I don't have any ild file that can simulate maximum or minimum voltage in LFI player.
I test it with max.wav file. I cannot turn on/off inverting option in WMP.
I figured out why I couldn't achieve negative potential at output of opamps.
There is diode (D1) that prevents current to flow in opposite direction.
Ok, I soldered diode in opposite way and now I can achieve 0V when max.wav is paused and -5V when open max.wav.
Voltage changes linearly as I move volume slider.
But when I connected dummy load at output of driver another problem occurred.
Current trough dummy load was about 2A and I expected only 1.2A.
I used R37 pot (see in schematic) to lower current down to 1.2A (that is calculated current that should flow if RSENSE is 1ohm).
OK, I connected LED and it's off when stop max.wav, and LED turns on when start max.wav. That is what I wanted......but brightness doesn't change linearly.
LED turns on from 95-100% of volume.
When I start LFI player and play any ILD file I can notice dim pulsing light coming from LED. Same thing happens when I turn on inverting function.
I think that problem is nonlinear output from analog driver.
Can anyone see what is problem now?
Here is link for schematic again...
http://www.speedyshare.com/files/24601242/Zavrsen.pdf
Senior Member
I never said you were talking about galvo op amps. While your color amps are not differential, they certainly can output +/- 5V. Differential output (two outputs, one inverted) is a different concept from bipolar output (one output that can swing + or -). The Galvo amps you have there are differential bipolar and your color amps are just bipolar.
That's ok, then just set it for -5V and 0 while playing the wav, and use the invert setting for those channels in EzAudDac.ini for LFI player. You could also by pass the inverting amp (second amp) for your color channels.And I don't have any ild file that can simulate maximum or minimum voltage in LFI player.
I test it with max.wav file. I cannot turn on/off inverting option in WMP.
You need to troubleshoot the correction amp separately from the driver. Only after the amp is tuned should you start on the driver. When doing driver design, an oscilloscope is necessary.
But when I connected dummy load at output of driver another problem occurred.
Current trough dummy load was about 2A and I expected only 1.2A.
I used R37 pot (see in schematic) to lower current down to 1.2A (that is calculated current that should flow if RSENSE is 1ohm).
OK, I connected LED and it's off when stop max.wav, and LED turns on when start max.wav. That is what I wanted......but brightness doesn't change linearly.
LED turns on from 95-100% of volume.
good luck!
Senior Member
OK, I wired the first stage of the Benm circuit on a breadboard and I was able to get 0 and +5v with max.wav. It took about 5 or 6 attempts, because the threshold and gain settings affect each other. After the inverter stage it should be 0 and -5v (measured before D1).
The purpose of D1 is to protect the CA3140N from negative voltage so the cathode of D1 must be connected to R17 as your print shows to prevent damage to the CA3140N.
The first stage was designed for negative signals (max.wav), you added an inverter, so you DO NOT want to set the invert option in EZAudDac.ini.
I've attached 2 test signals PosMax (full positive in all 6 ch) and White Circle (full screen circle)
Dean
Junior Member
Yes, they can give me +5V when playing max.wav, but cannot adjust it to get 0V when I pause max.wav. But can adjust -5V and 0V.
That is what I did, but as I mentioned in last post I can see only dim pulsing light.
Yes, opamp is tuned, it gives me 0-(-5V) and output is linear. But when I connect "analog driver" part it stops being linear.
If I connect cathode of D1 to R17 then I get 0V at output because D1 prevents current to flow in opposite direction. But if I remove second opamp I should get 5V and then I should be able connect cathode of D1 to R17.
I think that I'm going to pause this project for now. I started college in another city, and I don't have enough free time or money to play with electronics.
Probably going to start over....make new schematics and PCB....
Thanks for these files, they will be helpful.
Senior Member
Removing the inverter may simplify things, but you should replace the CA3140N if it wasIf I connect cathode of D1 to R17 then I get 0V at output because D1 prevents current to flow in opposite direction. But if I remove second opamp I should get 5V and then I should be able connect cathode of D1 to R17.
exposed to negative voltage.
Dean
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