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ArcticMyst Security by Avery

DDl driver with low voltage <6V ?

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Hello !! (from France). This forum is full of excellent idea and ressource, its an honour to be here  :)
I have a question, or remark :D
DDL driver need at last 6V to be full operational, that 's why we need 2x 3V CR123 battery with a mxdl Host. To higher voltage just add few 1n4001 in serie in circuit to lower voltage.
Its for low voltage that there is a problem (for me  ::))
I think that Cr123 battery are not the most choice to run laser (in my opinion) because they cost more than standart alcaline battery, and have shorten life time (if we compare to LR20 which are cheap monster) due to high power of laser consumption. With CR123, the advantage is that we can reach 6V with only 2 cell and have a nice host full design.
If we look a DX, they sold "crappy " flashlamp witch run at 2D cell or 3D (i dont find 4D, it will be very long , like Maglite type in picture), okay we got a poor lamp for a high $$ laser but i think that we spare some $$ with cheap lr20 (20.000 mah!).

So for example, i can use 3D cell with the crappy flashlight, i have 4.5V, but driver need 6. Is there a solution to "light" this driver? (removing 1 diode for example?) i can't test a this time  :p

im expecting problem to post image for first time and sorry for mistake in my post =)
 

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There really is no way to run the lm317 with a lower voltage. Its not the diode which is soaking up voltage, it is the LM317 itself. And we know without the LM317 we no longer have a current regulated driver and we risk killing the diode. I believe the dropout on the lm317 is around 2.25v. The red laser diodes take just under 4v (I think...) to operate. So 4v, adding on the ~2v dropout for the lm317 and you get 6v. The only diode you could run with less voltage (4.5 with an lm317 would be perfect) would be an infrared diode, since they only take slightly over 2v to operate.

Hope that helped a bit! :D
 
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Hey, welcome to the forum :)

I know its not as much fun if you don't make it yourself. And to be honest, the only forum on this website that I really follow is this one. But, there is a driver that will do what you want and drlava will sell it to you. Check out this thread: http://www.laserpointerforums.com/forums/YaBB.pl?num=1209418066/0

If you search for boost driver or something similar you will find another thread with some circuits that will do what you want also. The circuits use parts that aren't as easy to get as the LM317 driver and are mostly surface mount and will often require you to make a PCB in order to build them. If you really want to build it yourself though, I'm sure it will be much more rewarding than purchasing a pre made driver.

Have fun, and hope this was helpful.
 

chido

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You need more than 6v to run a DDL driver, 6v is the minimum voltage. The LM317 (approximately) keeps 3v for itself, and in average, a red laser diode takes another 3v. So in total you need 6v to power the driver, but what happens if those 6v drop? The LM317 will still take 3v but the diode will take less voltage, say 2.6v which would make it weaker. As the batteries' voltage keeps dropping the voltage going to the diode will keep decreasing. You need to power the LM317 with more than 6v, that's why people use rechargeable CR123s which are 3.6v each instead of the CR123s which are only 3v each. Two RCR123s should give you a total of 7.2v and thus they need to drop more than 1.2v before the LM317 starts dropping out.
 

roSSco

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chido said:
You need more than 6v to run a DDL driver, 6v is the minimum voltage. The LM317 (approximately) keeps 3v for itself, and in average, a red laser diode takes another 3v. So in total you need 6v to power the driver, but what happens if those 6v drop? The LM317 will still take 3v but the diode will take less voltage, say 2.6v which would make it weaker. As the batteries' voltage keeps dropping the voltage going to the diode will keep decreasing. You need to power the LM317 with more than 6v, that's why people use rechargeable CR123s which are 3.6v each instead of the CR123s which are only 3v each. Two RCR123s should give you a total of 7.2v and thus they need to drop more than 1.2v before the LM317 starts dropping out.
I've read this so many times that I probably repeat it in my sleep. :D
 

chido

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Yeah you're right. People should read the entire DDL driver thread before asking questions.
Or at least DDL should edit his first post saying 6v is the minimum voltage, specify that the LM317 needs more than that to power a red diode for a long period of time.
 
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Thx for DrLava Driver its exactly what i need, but i prefer to try to build a new one =)

i  read the 29 topic page of ddl driver but i was not convinced in the choice of lm317. Could we use an other voltage regulator with low dropout ?
 

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There are lower dropout regulators, but remember we are using the LM317 as a current regulator not as a voltage regulator. I'm not sure if other voltage regulators can also be used as current regulators like the lm317 can, so make sure to do your research before deciding :cool:
 




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