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Curious. Just checking, you do have the LOC's polarisation set perfectly? And the PBS is the right way around right? If you mask the straight through LOC with a piece of black card do you see the any light from the other LOC/PBS hit the card? Just a thought.
In my quad, I am running 4 LOC at 450mA and thus far not a single LOC failure.
Quote:
Originally Posted by dnar
dnar,
I did as you said. I rotated each diode till I had maximum output from the PBS. The output forms an almost perfect "+", but oval.
I placed a black card in front of the through axis LOC and there was no sign of beam reflection from the other LOC.
I placed the card in front of the 90-degree axis LOC and there was a very small reflection from the through-axis LOC.
I really don't see how the through-axis LOC could reflect to the 90 degree axis?
Could the through-axis LOC be slightly off in its polarization? Maybe I don't have it turned enough?
Thanks for all the inputs!
I blew another LOC and I found out why.
While playing back a show, I monitored the voltage drop across each 1-ohm resistor. This would show me the current each LOC was getting. A series of patterns was displayed and I noticed the current to each LOC was over 650mA!!
I am using Spaghetti and set the min and max output in the projector settings and the current was within limits. I set the upper limit at 300mA and the lower at 14mA.
I am still not sure why the current went so high while displaying multiple patterns. i repeated the pattern and the current went high again and the through axis LOC blew.
I ordered 3 more Flexmod P3s.
-magman116
good to know, will built my quad red soon and will keep this in mind.
Michel
A couple of questions.
What voltage are you running the flex mods at?
Are you sure they are 1 ohm? might want to bump it up a little 1.5 ohm maybe?
How good is the PBS? Is it ar coated?
And double check the polarization. It will be arc seconds rotation to get it dead nuts. Do you have a power meter? Or can you rig a Si photodiode with a ND filter to get a relitive reading? you should optimize each diode rotation with a meter if possible.
Do you have lasorbs? If not you should have them just for peace of mind, and they work.
chad
Right, I have heard a few issues with P3 killing diodes when modulated.Quote:
Originally Posted by magman116
Tonight I will setup a test P3, with parallel test loads (1n4004's) and a function generator. Will report back.
I want to ensure I don't blow my quad once I get my projector running!
BTW, I recall Heroic was involved sorting a similar issue for some one else, I recall they fitted some C to the LD's but they were in series from memory.
Hi Chad,Quote:
Originally Posted by chad
I have a 9V 5A regulated switching power supply that runs my 2 LOCs, a 1W 445nm turned way down, and a 200mW 532nm. It is very stable with very little ac ripply.
The 1ohm resistors are 1% 3W.
The PBS is from LASERWAVE and is AR coated or it is supposed to be.
Many years ago, I made a laser power meter using a photo diode. I compared it with a power meter we used at work and noted the delta. While not as accurate, it is pretty close using the offset. I mainly use it as a general reference when tuning or adjusting the driver.
I did not use it to setup the polarization through the PBS; good idea.
I have thought about using LASORBS for the LOCs, but only have them on the 445nm and the 532nm. Seeing how I have already blown 5 LOCs, it would make sense to use them. I will be getting some 642nm 150mw diodes from Francisco to replace my LOCs soon.
It will be interesting to here your findings.Quote:
Originally Posted by dnar
I did some testing here with an o-scope and different software. I was observing the ILDA modulation line for each color, one at a time, and the output from the driver.
It was interesting to note that NLS, NE-Laserscan, and Spaghetti all have different pulse width outputs. The voltage was 5V for each waveform, but the on-time was different. NLS had the longest on-time, and Spaghetti had the shortest.
This could account for different current draw while running different programs. With Spaghetti, when playing back complex scenes, the pulse width would increase quite a bit.
I created a waveform scene all red ilda file, then played in the different programs. In NLS the current to the LOCs wound run about 380mA, but in Spaghetti is was around 205mA. Why?
Curious. Did you apply a "colour change" effect to the scene? If so, Spaghetti alters the chroma but maintains the luminance value. The result is that when you change the colour of a frame, you drop brightness.Quote:
Originally Posted by magman116
Quote:
Originally Posted by magman116
Did you setup the max current of the flexmod with an external +5VDC on the mod input?
No matter what any DAC is outputting with whatever software is used, if the out current of the flexmod exceeds the set max current then this is obviously a problem with the current limiting of the flexmod. Probably an HF resonance thing going on here. If you’re using lasorbs try not using lasorbs.
I just read up on the lasorb and I couldn’t find any information on multi diode setups with a single driver. But from what I gather on the Lasorb functionality, it doesn’t seem to be a good Idea to use these in Parallel configurations. If a Lasorb acts out its protective function on one diode the other could get a peak current due to the first being shorted and shortly after the second lasorb becoming active causing instability in the circuit and start a resonance between the Lasorbs and driver.
Reading the datasheets of the lasorb it appears these are laid out for single diode protection with single drivers.