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Hmm Blu-Ray problems.

xanxan

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I have a situation with the driver I have where the Blu-ray Diode starts but instantly turns off. It I apply power to it and it briefly flashes and the is off with current to it. When I check the voltage across the load of the LD it is about 2.4 Volts. The Resistor is set and 33 ohms and the Driver is set up in same config as DDL driver config. Any help would be appreciated it.
 





jayrob

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xanxan said:
I have a situation with the driver I have where the Blu-ray Diode starts but instantly turns off. It I apply power to it and it briefly flashes and the is off with current to it. When I check the voltage across the load  of the LD it is about 2.4 Volts. The Resistor is set and 33 ohms and the Driver is set up in same config as DDL driver config. Any help would be appreciated it.

If you are using an LM317 (DDL style) driver, with a 33 ohm resistor. This will give you about 38mA's current. For a blu-ray diode, you will need to supply the driver with at least 9 volts battery supply. What batteries are you using to run your blu-ray?
Jay

P.S. If you are using the MXDL that I showed for the blu-ray build:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1202168096/0
It takes 3 X AAA sized batteries, you need to use the 3.6 volt 10440 batteries. Which are the same size as AAA, but the voltage is 3.6 per battery, not 1.5, like a normal AAA. Three normal AAA batteries, will not run your blu-ray.
 

jayrob

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xanxan said:
For my test Circuit I am using a 9 volt battery at 9.3 volts.

If your driver is built correctly, and the battery is not low, you should have 4.5 volts at the LD. If you are getting a reading of less than 3 volts, your LD may be ok. Disconnect the LD, and double check the driver. With out the LD connected, you should get a 9 volt reading, and about 38mA's current. If your cap is built into the driver, make sure you discharge it before connecting the LD...
Jay
 

xanxan

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With the LD disconnected I read about 8.7v. If I put 12 volts on the other end should it matter?
 

jayrob

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xanxan said:
With the LD disconnected I read about  8.7v. If I put 12 volts on the other end should it matter?

I run my blu-rays with a 12.6 volt supply (3.6 volt batteries X 3 - fully charged at 4.2 volts a piece) The LM317 can handle even more voltage. But, not necessary. Sounds like your battery is low. Try 12 volts, and check to see if you get 4.5 volts across the LD. Since your not using a pot in your driver, your current should be fixed at around 38mA's using the 33 ohm resistor. If your not getting 4.5 volts at the LD, then your battery is low, or something is wrong with your driver...
Jay
 

chido

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It doesn't matter if you put in 12v, 9 is enough, just make sure the battery is in good condition. You can use 12v if you want to, but you're going to need to heatsink the LM317. The reading you get without the diode connected is of no use, connect your diode again and measure the CURRENT, don't worry too much about the voltage, with this circuit just think current. ;)
Start with your pot at the highest resistance, then turn it down to increase the current going to the diode. As soon as the diode lights up keep going until you reach 10mA more than when your diode began to lase.
Also, how are you measuring the voltage? You're supposed to do it like in this schematic:

EDIT: Remember to short out the capacitor before reconnecting your LD. ;)

clip_image001.jpg
 

jayrob

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chido, he is not using an adjustable current driver. Or, are you? Because that could explain it. If you have a pot, and a 33 ohm resistor, you probably have too much resistance...
Jay
 

chido

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OH, never mind then, I should've read the thread more closely. :-[
I do recommend you get a pot as not all blu ray diodes will lase at the same current, some will lase at 20mA, others at 30, it depends.
 
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Hmm

Keep in mind that this circuit is designed to regulate current NOT voltage, thus if you want 3v on the diode, its designed to take 7v on the input. It's my understanding that the LM317 in this circuit is going to drop 3 to 3.5 volts as the LM317 inherently consumes this. the design of the circuit is to regulate current and as such can't be expected to regulate current and voltage at the same time.

SN
 

jayrob

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SuperNova said:
Hmm

Keep in mind that this circuit is designed to regulate current NOT voltage, thus if you want 3v on the diode, its designed to take 7v on the input.  It's my understanding that the LM317 in this circuit is going to drop 3 to 3.5 volts as the LM317 inherently consumes this.  the design of the circuit is to regulate current and as such can't be expected to regulate current and voltage at the same time.

SN

Yes, it regulates current, BY regulating the voltage (1.25) So, if the load requires more voltage than is supplied, the LM317 'drops out'...
Jay
 
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Sorry

But as I understand it, the circuit needs 6.5+v to actually deliver 2.8v to the diode. If i am wrong, forgive me, but reading the ddl design of it in the original drawing / thread regarding a red, it loses 3 volts inherent to the internals of the LM317, when used in this capacity / design.

Not familiar with blues, I would guess to up the in volts to + 3 over what you want the diode to see, then test it and if thats the correct out volts, then try a blu LD.

SN
 

chido

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The LM317 always keeps 3v to itself, when using red diodes you need a minimum of 6v input since red diodes need approx. 3v to work, but it's recommended to use a power supply that's at least 7v, otherwise the LM317 starts dropping out very quckly. For bluray diodes you need at least 7.5v input since these need approx. 4.5v to work, but again, same deal as the reds, it's recommended you put in 9v. Since bluray diodes don't need a lot of current you can use a regular 9v battery, but reds require more current, so you need to use nimh or lithium batteries since their mAh rating is usually higher than that of normal 9v batteries.
 

jayrob

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SuperNova said:
Sorry

But as I understand it, the circuit needs 6.5+v to actually deliver 2.8v to the diode.  If i am wrong, forgive me, but reading the ddl design of it in the original drawing / thread regarding a red, it loses 3 volts inherent to the internals of the LM317, when used in this capacity / design.

Not familiar with blues, I would guess to up the in volts to + 3 over what you want the diode to see, then test it and if thats the correct out volts, then try a blu LD.

SN

Yes, you are correct. Since the blu-ray diodes take 4.5 to 5 volts, and the curcuit still takes at least 3 volts, you need a supply of about 9 volts. Otherwise, the LM317, will not be able to regulate the current, because it won't be able to regulate the 1.25 volts across its sense resistor. (between Vout and Adj)
Jay
 
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chido said:
The LM317 always keeps 3v to itself, when using red diodes you need a minimum of 6v input since red diodes need approx. 3v to work, but it's recommended to use a power supply that's at least 7v, otherwise the LM317 starts dropping out very quckly. For bluray diodes you need at least 7.5v input since these need approx. 4.5v to work, but again, same deal as the reds, it's recommended you put in 9v. Since bluray diodes don't need a lot of current you can use a regular 9v battery, but reds require more current, so you need to use nimh or lithium batteries since their mAh rating is usually higher than that of normal 9v batteries.


Maybe I am wrong, but if it was me, i would look to put 4.5 + 3ish = 8 to 9 v on it as I can't expect the circuit to lose more then 3v. I agree I would stack some lithium batteries as compared to a alkaline 9v.

SN
 




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