DAC output voltages

[riyalasers]

Gary,
Write please in detail:
- did you measure differential voltage (between "positive" and "negative" lines?
- or did you measure in relation to "ground"? Did you connect a "negative" line to "Ground" in this case?

[carmangary]

I measured across the color differential pins (+ & -). I did not reference ground. I actually took the measurement at the modulation input at the laser. It's possible I could get different readings if there was nothing connected. Have you tried with your boards when powered by USB? What do you get?

[riyalasers]

Gary,

...
I measured across the color differential pins (+ & -). I did not reference ground. I actually took the measurement at the modulation input at the laser.
...

Ok, then two variants:
- software, which you use, make not correct control ("black" points on frame... some other...). Can you use direct control under TestRIYA program?
- low input resistance of your laser module. Can you meter voltage without laser?



... Have you tried with your boards when powered by USB? What do you get?
...

Yes, of course
OP AMPs is powered from DC/DC convertor in RIYA Multibus controllers. For they is not different: power from USB line, or from external PSU: controller "as whole" required ~150mA; it is no problem for USB interface

[carmangary]

I'm not sure why it is that way but I wanted to point it out so everyone is aware. I encourage others (end users and DAC makers) to take their own measurements. The fact that with the same output the EasyLase outputs 4.8v and the Moncha and Riya DACs outputs 4.4v is the main thing to consider since that alone shows that different DACs behave differently. It's probably not too bad of a thing that voltage is a little low since it will keep the laser happier. Better low then too high.

[sbk]

Just to let you know, the output of the FB3 is just above 5V, so that's perfect.

I was secretely hoping it was less, so I can gain some laser power here, but finally there's nothing to do

[riyalasers]

Gary,
analyse problem is impossible with value of multimeter measurement only, without data about program which you use, and without features of controllers:
- you not answered what program and what frame for testing you used;
- have you function "black points" in begin and in end of frame in software which you use? is this function enable or disable?
- next, in different with other controllers, RIYA Multibus controllers have additional embedded "black points" function in hardware (in controller) (look picture).



What value you setted in this function within testing?


So, make please "Black point function" in RIYA_Settings program = 0, after it run TestRIYA software (it will send to controller only wisible points), meter voltage and write please result - I will know, is broken our controller, or it is features of frame which you translate within testing.

[afrob]

@carmangary:
Have you measured the input impedance of your lasers? With Easylase you get a voltage drop of about 0.1 volts for every miliamp of current you draw from the output. I would guess it is 1k2 Ohms which is not really high. If you use a real difference amplifier with high input impedance for your ILDA input the voltage drop will proably go away.

Greetings,
afrob