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FrozenGate by Avery

Blanking DDL

You're definitely right.. that's not a usable schematic, and I didn't intend for it to be. It's just the only fast way I could think of to help you visualize what needs to be done in order to see some decent modulation rates.. The circuit design and fine tuning is up to you..

Personally I recommend using the schematic I posted on reply #24. It contains all the necessary elements to safely modulate up to 20kHz I believe.. All you need is a few common components (resistors, diodes, transistors), an op-amp and an optocoupler.

As I said previously, if you just replace the LM317 portion of the circuit (red circled portion below) with any standard DDL circuit and just add the rest to it starting with the 10k pot directly after, it simplifies the circuit even more.

That circuit will allow for safe fast modulation and I don't think it can be done as cleanly with any simpler circuitry. Don't let the apparent complexity fool you. If you look closely, you'll see that it's really not much at all.

ModulatingDDL2.jpg
 





Well first problem is that the diode isn't connected to GND, which I need it to be.
The diodes - "Si-Mi", what does that mean, just any silicon diode?
All these arrows pointing up, do they go to the powersupply+?
What's the deal with the 5W resistor?
Will it work on blu-ray?

Thanks. ;)
 
FireMyLaser said:
Well first problem is that the diode isn't connected to GND, which I need it to be.

I'm curious as to why it must go to ground. You can hook any laser diode up in this manner as long as you observe correct polarity (I'll insert another picture to help you visualize what I'm saying here..)

The diodes - "Si-Mi", what does that mean, just any silicon diode?

Yes. Any silicon diode should work fine as long as it will handle whatever current is going through it at that point. 1n4001 diodes should work in most cases.

All these arrows pointing up, do they go to the powersupply+?

Correct

What's the deal with the 5W resistor?

my guess would be that it is required to dissipate the power through it at that point in the circuit. You probably wouldn't necessarily need a 5W resistor unless you're using a diode with a current draw over 500-750mA.


Will it work on blu-ray?

It should work with any laser diode provided you test and calibrate it with a dummy load first..


Thanks. ;)
Click to expand...

I removed the diode from the circuit pictured below and replaced it with empty terminals. If you visualize the empty terminals, then you can hook any laser diode up to those terminals as long as you observe the correct polarity..

diodedriverwTTL3.jpg
 
Thanks!

You misunderstood one question. The heatsink on the red LD is negative and is connected to the metal base. The violet LD works either way or isolated but I prefer negative caseing. The green laser has a positive heatsink but I've isolated that from the base with plastic screws. So in order to make this work I need the modulation to be on the positive side of the diodes, not the negative. I could isolate the other modules but that's not the way I planned.

Also those pots are a little crazy, 10-gang. Hardly common.
 
FireMyLaser said:
Thanks!

You misunderstood one question. The heatsink on the red LD is negative and is connected to the metal base. The violet LD works either way or isolated but I prefer negative caseing. The green laser has a positive heatsink but I've isolated that from the base with plastic screws. So in order to make this work I need the modulation to be on the positive side of the diodes, not the negative. I could isolate the other modules but that's not the way I planned.

Also those pots are a little crazy, 10-gang. Hardly common.
Click to expand...


Regarding the pots, if they are ganged it's to handle a very high power load. For hobbyist purposes, just use normal pots.. (personally I think they are labeled incorrectly, or maybe it's because of some German language quirk..)

Regarding your ground problem, you could just isolate the modules from ground themselves. Mounting them using plastic instead of metal might be one way to do this. Since you isolated the green case from ground, just connect the positive output of this driver to the case (I trust you've removed the green module from it's attached driver?).. As for the other modules, just connect the pin that needs to be grounded to the negative output of the driver..

I get that this may alter your original plan, it just comes down to whether it would be simpler to adapt your original plan to the driver, or to design a whole new driver to work with your original plan.. Whatever is simplest and most economical would be my choice.
 
Yes, the original green driver is removed and is working with the circuit in reply #25 with a threshold resistor too.

I'll gather the parts and test this, but for now, if the current circuit (reply #25/27) is safe I'll continue using it.
 
FireMyLaser said:
Yes, the original green driver is removed and is working with the circuit in reply #25 with a threshold resistor too.

I'll gather the parts and test this, but for now, if the current circuit (reply #25/27) is safe I'll continue using it.
Click to expand...

That sounds like a good plan.. If you have access to an oscilloscope, I'd try checking the output waveform of your driver for any spikes. If there are none, then it should be good for the long run. If there are spikes, then redesigning your driver will be necessary for long term usage..
 
I don't have an oscilloscope. :(

I'll just let a PHR diode pulse up and down at 100mA without a threshold resistor 24h/day for a while starting now.
 
You might be getting a minor spike going by the line transient graph of the LM1117 but I am pretty sure that the rkcstr has some decent capacitors across the output and as long as you aren't running the diode on the edge it should be fine.
capturerdb.jpg
 
You should measure the spikes as current, not voltage though. A small rise in voltage over a diode can represent very significant rise in current.

Also, the graph above depicts a regulator that stays very well within its operating input voltage limits. When you start blanking TTL style, you will basically switch is input from ground to maximum, passing through an area of non-regulation.

I'll just let a PHR diode pulse up and down at 100mA without a threshold resistor 24h/day for a while starting now.
Click to expand...

I suppose it will be fine if your pulses are good - i've done this with red burner diodes, those didnt die on me in the process.
 
It seems to be working, the diode is still alive. I actually took the time and made three drivers and tested it on my RGV. It's pretty good, though at a maximum current going thought one of the drivers at 480mA and another at 385mA, the BC337 transistors gets really hot. I don't dare to run it more than 5 minutes at a time. Also I changed the RGB-IC with another which has a much higher frequency (probably above 1kHz) and it seems to work as well. Though it doesn't fade between the colours as good as it did with the LEDs. The lases are on for too long. So instead of fading from red to yellow, green, cyan, violet and magenta, it goes from yellow to cyan to magenta. I can't describe the problem any better, I will make a short video soon.

Current schematic:
bc3373-1-1.jpg


Great thanks to everyone who helped! I really appreciated it!
 
You might want to try removing a few capacitors/reducing their values to see if you can get better color mixing. When you PWM too fast sometimes the capacitors can store enough power to keep the diode going between pulses. Effectively it reduces the duty cycles that actually vary the brightness from 10-30% or so.
 
About the transistors running hot: how much base current does that photodiode deliver connected like that? I'd suspect you're not driving the transistor to saturation, hence it drops voltage and heats up. I would insert a 2 ohm (or so) resistor in the collector lead to remedy this, since you can miss the voltage for the driver easily.

Also, reduce the capacitors - especially the 10 uF one. Even if they dont cause the problem with fading, that one will ask a lot from the poor bc337 driving it!
 
I changed the base-resistor from 1K to 470 ohm and it did the trick! To fix the problem with the lasers staying on for too long, I added a 10K pot to the optocoupler-LED and adjusted it till normal. I've done nothing to the capacitors..
 
FireMyLaser said:
I changed the base-resistor from 1K to 470 ohm and it did the trick! To fix the problem with the lasers staying on for too long, I added a 10K pot to the optocoupler-LED and adjusted it till normal. I've done nothing to the capacitors..
Click to expand...
Which ''base-resistor'' do you mean? I guess the one that goes to the 10k "abschaltstrom'' potentiometer?
 
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