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Running Multiple Lser Diodes. (NUBM08)
- Thread starter Bowler
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You can get LM 338T regulators for cheap and they will do 5 amps, yes to run all your laser diodes in series you need over 40 volts, if using LM 317's you just tie your V in pins together and your adj pins together that connect to your first diode + then daisy chain them all in series.
0.8 ohms between the center pin ( v-out ) and left pin ( adj ) will give you 1.5 amps if using the LM 317 , then tie all your right side pins together ( V - in ) and all your left side pins together ( adj ) those run to your first LD + that are wired in series. 4.5 amps total for each diode with 3 lm317's in series @ 1.5a each.
Note your center pin and mounting tab are common and you will need over 40 volts to run them all in series, but if you short any of them and you can blow all your laser diodes.
You have to use heat transferring electrical isolators to mount them. DO NOT TIE YOUR CENTER PINS TOGETHER!
I would use a LM 338T for each diode and use 2 x 3.7 volt Li ions for each diode just to be safe, or run them all in series if you have say, a 48 volt battery.
But to answer your question your right side V in pins would tie together if using LM 317's and your left side ( ADJ ) would tie together with each LM 317 having it's own 0.8 ohm ( 2 watt ) resistor between the left side ADJ and the center V-OUT, but if you short anything you fry it all.
0.8 ohms between the center pin ( v-out ) and left pin ( adj ) will give you 1.5 amps if using the LM 317 , then tie all your right side pins together ( V - in ) and all your left side pins together ( adj ) those run to your first LD + that are wired in series. 4.5 amps total for each diode with 3 lm317's in series @ 1.5a each.
Note your center pin and mounting tab are common and you will need over 40 volts to run them all in series, but if you short any of them and you can blow all your laser diodes.
You have to use heat transferring electrical isolators to mount them. DO NOT TIE YOUR CENTER PINS TOGETHER!
I would use a LM 338T for each diode and use 2 x 3.7 volt Li ions for each diode just to be safe, or run them all in series if you have say, a 48 volt battery.
But to answer your question your right side V in pins would tie together if using LM 317's and your left side ( ADJ ) would tie together with each LM 317 having it's own 0.8 ohm ( 2 watt ) resistor between the left side ADJ and the center V-OUT, but if you short anything you fry it all.
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diachi
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LM338 is a good suggestion. They are cheap and operate just like the LM317s, the same calculations and circuits work with both. Although each regulator will need some heatsinking at those sorts of currents.
Thanks for adding that RCB, +rep ... don't know why the LM338 didn't come to mind, I have a stack of them and I usually suggest them for things like these...
The other option is just to buy 8 off the shelf drivers and wire the inputs up in parallel to a beefy Lithium battery. Job done, nice and simple ... although more expensive.
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Hi Red cheers!
It would seem you knowledge is very valuable. Would it be possible if I could get this on a wiring diagram of your suggested idea as I feel this would be better ? Nothing special, just pen on paper and just make a circuit which is all clear for me. That would be great. I don't know if you can upload pics on here; so my email is joshuabowler@hotmail.co.uk please feel free to drop that by
I'm probably working on this project this weekend as its being delivered tomorrow !
It would seem you knowledge is very valuable. Would it be possible if I could get this on a wiring diagram of your suggested idea as I feel this would be better ? Nothing special, just pen on paper and just make a circuit which is all clear for me. That would be great. I don't know if you can upload pics on here; so my email is joshuabowler@hotmail.co.uk please feel free to drop that by
I'm probably working on this project this weekend as its being delivered tomorrow !
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What battery are you planning to use? 7.5V ok then you want to do what styro did.
Here's a simple explanation, you can tie three 317's together by tying together the left pins that go to your laser diode + and tying together your right side pins and running those to your battery + Your 1 ohm resistors connects between each A and O, each 317 gets it's own 1 ohm resistor but the O pins must not touch anything else or the mounting tabs must not touch as the center pin and mounting tab are common and are not connected in parallel like the outside pins are, this is imperative as not to blow your laser diode.
Your battery ground attaches to your laser diodes - negative posts.
If you run 8 laser diodes in series they will all get the same current as limited by the 3 paralleled LM 317's that you set with a resistor between your center pin and your left pin (adj) that attaches to your first diodes + but you will need 8 times the voltage, but you are not doing that.
Styro used 3 x LM 317's in parallel for each diode. That way a short will only kill one diode, and he skipped the isolators and heat sinking. I think he went with 1.25 amps each. That would be a simple 1 ohm resistor between the center pin of each LM 317 and the left pin ( adj ) that you tie the 3 of together and connect to your laser diode's + Do not tie your center pins together or let the mounting tabs touch. If you wanted 1.5 amps each rather than 1.25 you could parallel a 1 ohm and 5 ohm resistor between A and O but you will have plenty of heat with 3.75a each, whatever you do give all 3 LM 317's the same amount of resistors.
You need 2 watt size resistors. Those are the ceramic rectangles hanging from his cluster in the video. If you use 2 watt size resistors of 1 ohm you will get about 1.25 amps each x 3 is 3.75 amps for each parallel of 3 LM 317's, a set of 3 for each of 8 diodes 24 total then you can use a hobby battery pack of 7.4 volts that will carry 35 amps.
Heat sinking for your block of NUBM08's and Laser safety glasses that attenuate 450nm are a must , you can use a large switch on your positive battery wire that connects to all 8 of your 3 LM 317 parallels of 3 each.
Obviously this is not a series arrangement, each diode has 3 LM 317's , left pin to the + and ground from the battery to the - , be sure to switch the positive wire from the battery pack with a high current switch.
Here's a simple explanation, you can tie three 317's together by tying together the left pins that go to your laser diode + and tying together your right side pins and running those to your battery + Your 1 ohm resistors connects between each A and O, each 317 gets it's own 1 ohm resistor but the O pins must not touch anything else or the mounting tabs must not touch as the center pin and mounting tab are common and are not connected in parallel like the outside pins are, this is imperative as not to blow your laser diode.
Your battery ground attaches to your laser diodes - negative posts.
If you run 8 laser diodes in series they will all get the same current as limited by the 3 paralleled LM 317's that you set with a resistor between your center pin and your left pin (adj) that attaches to your first diodes + but you will need 8 times the voltage, but you are not doing that.
Styro used 3 x LM 317's in parallel for each diode. That way a short will only kill one diode, and he skipped the isolators and heat sinking. I think he went with 1.25 amps each. That would be a simple 1 ohm resistor between the center pin of each LM 317 and the left pin ( adj ) that you tie the 3 of together and connect to your laser diode's + Do not tie your center pins together or let the mounting tabs touch. If you wanted 1.5 amps each rather than 1.25 you could parallel a 1 ohm and 5 ohm resistor between A and O but you will have plenty of heat with 3.75a each, whatever you do give all 3 LM 317's the same amount of resistors.
You need 2 watt size resistors. Those are the ceramic rectangles hanging from his cluster in the video. If you use 2 watt size resistors of 1 ohm you will get about 1.25 amps each x 3 is 3.75 amps for each parallel of 3 LM 317's, a set of 3 for each of 8 diodes 24 total then you can use a hobby battery pack of 7.4 volts that will carry 35 amps.
Heat sinking for your block of NUBM08's and Laser safety glasses that attenuate 450nm are a must , you can use a large switch on your positive battery wire that connects to all 8 of your 3 LM 317 parallels of 3 each.
Obviously this is not a series arrangement, each diode has 3 LM 317's , left pin to the + and ground from the battery to the - , be sure to switch the positive wire from the battery pack with a high current switch.
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Please go to your 1st post, 3rd line and correct the spelling to N1ch1x, or backspace out the name completly, we all know what an 08 block is.
Just use the edit button at the bottom, you must be signed in, correct the spelling and click save changes, you can click the link below, Thanks.
http://laserpointerforums.com/f44/running-multiple-lser-diodes-nubm08-99263.html#post1452131
Just use the edit button at the bottom, you must be signed in, correct the spelling and click save changes, you can click the link below, Thanks.
http://laserpointerforums.com/f44/running-multiple-lser-diodes-nubm08-99263.html#post1452131
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diachi
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Hi Red,
I've had some free time now and drawn up the wiring diagram for approval.
My only remarks are.... The 08 Datasheet says the Absolute Max Current is 3.5. And with 3 x 1 ohm resistor = 3.75 its 0.25 over. what do you think? I don't want to blow these boys! 1.1 ohm would cover it. what do you think?
and as far as battery power goes. The max is 38V / 8 LD = 4.75 + the drop out 1.25V = 6V supply suitable. What do you think?
Also me having a big 250A capability will work on this circuit wouldn't it. Its not going to melt the 1 ohm resistors?
Also, I have only drawn the wiring up to One LD; of course I will do this exact same to the other 7 and wire them to the + & - of the supply
I've marked in the Capacitors 0.1uF as I think this is a good idea to stop any sudden surges that could damage the LD And I will put a 1uF Cap on the out. I think I've put it in the wrong place but I'll sort that out another time. See image below!
https://s17.postimg.org/6zfubhpbz/Wiring_D.jpg
Thanks again.
I've had some free time now and drawn up the wiring diagram for approval.
My only remarks are.... The 08 Datasheet says the Absolute Max Current is 3.5. And with 3 x 1 ohm resistor = 3.75 its 0.25 over. what do you think? I don't want to blow these boys! 1.1 ohm would cover it. what do you think?
and as far as battery power goes. The max is 38V / 8 LD = 4.75 + the drop out 1.25V = 6V supply suitable. What do you think?
Also me having a big 250A capability will work on this circuit wouldn't it. Its not going to melt the 1 ohm resistors?
Also, I have only drawn the wiring up to One LD; of course I will do this exact same to the other 7 and wire them to the + & - of the supply
I've marked in the Capacitors 0.1uF as I think this is a good idea to stop any sudden surges that could damage the LD And I will put a 1uF Cap on the out. I think I've put it in the wrong place but I'll sort that out another time. See image below!
https://s17.postimg.org/6zfubhpbz/Wiring_D.jpg
Thanks again.
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This is a very expensive experiment you're undertaking here. You REALLY want to try this out with a $3 diode first to be sure you understand the concepts involved. Then scale it up. One fuckup here and you're out hundreds of dollars.
I don't know where you read that figure, but it's wrong. See datasheet page 9. Other datasheets have a graph to reference. It is typically ~2.25V+1.25V=3.5V where we run them, or 4-4.5V to be safe. Maybe even higher in some cases to account for lithium voltage sag.
I don't know where you read that figure, but it's wrong. See datasheet page 9. Other datasheets have a graph to reference. It is typically ~2.25V+1.25V=3.5V where we run them, or 4-4.5V to be safe. Maybe even higher in some cases to account for lithium voltage sag.
diachi
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Hi cyparagon,
What I'm going to do is do a full check sheet of the data and see what spec everything is and will work at.
Tbh red has answer most of my questions for me and shown me what I thought. I've done a lot of maths and I understand this stuff as I'm a qualified electrical engineer. However we did not study LD in my course! But all of the principles are there to most degree.
I think I will be fine, now I understand. The hardest thing is the learning curve; but once you know, it's easy. And it all seems pretty straight forward now.
Thank you for commenting one the correct drop out voltage. I will take this into consideration.
Cheers
What I'm going to do is do a full check sheet of the data and see what spec everything is and will work at.
Tbh red has answer most of my questions for me and shown me what I thought. I've done a lot of maths and I understand this stuff as I'm a qualified electrical engineer. However we did not study LD in my course! But all of the principles are there to most degree.
I think I will be fine, now I understand. The hardest thing is the learning curve; but once you know, it's easy. And it all seems pretty straight forward now.
Thank you for commenting one the correct drop out voltage. I will take this into consideration.
Cheers
- Joined
- Jul 10, 2015
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- Points
- 113
That's a good idea to practice with some inexpensive 660nm diodes, I used lm 317's to drive 660's many years back and each one had to be mounted with an isolator.
Look at this 317, see how the mounting screw has a isolator sleeve and a mica backing so it can mount to say, an aluminum housing without shorting out?
Look at the hardware, a heat transferring electrical isolator and a mounting screw sleeve are needed unless you did a temporary rig like styro did with 24 spare 317's in parallels of 3 just hanging, but they still must be insulated so as not to short out.
Another pic > LM317AT(1 item) | eBay
Also decide if you want to run your diodes is series or use say a LM 338T for each diode, I think 37.5 volts is the spec sheet limit for the 317 but I can't remember, you could do 2 banks of 4 but I would mount with an isolator a single LM 338T for each diode and use enough paralleled 7.4v - 8.4v li-ion packs to carry the load.
-------------edit-------------
As for the max rating of 3.5 amps each we typically overdrive based on the tested fold back, but stay at 3.5a or less if you like, but you will still have a lot of waste heat to deal with and that's a killer of laser diodes, you will need to be aware of your temp and limit your duty cycle or build in active cooling. 5 amps is the hard fold back, 4.0 to 4.5 amps is where most hobbyist run the 08 I do believe, also understand that removing the cans expose the dye to contaminants and can shorten lifespan, going to 3.75 amps is not a big deal in my opinion.
Look at this 317, see how the mounting screw has a isolator sleeve and a mica backing so it can mount to say, an aluminum housing without shorting out?
Look at the hardware, a heat transferring electrical isolator and a mounting screw sleeve are needed unless you did a temporary rig like styro did with 24 spare 317's in parallels of 3 just hanging, but they still must be insulated so as not to short out.
Another pic > LM317AT(1 item) | eBay
Also decide if you want to run your diodes is series or use say a LM 338T for each diode, I think 37.5 volts is the spec sheet limit for the 317 but I can't remember, you could do 2 banks of 4 but I would mount with an isolator a single LM 338T for each diode and use enough paralleled 7.4v - 8.4v li-ion packs to carry the load.
-------------edit-------------
As for the max rating of 3.5 amps each we typically overdrive based on the tested fold back, but stay at 3.5a or less if you like, but you will still have a lot of waste heat to deal with and that's a killer of laser diodes, you will need to be aware of your temp and limit your duty cycle or build in active cooling. 5 amps is the hard fold back, 4.0 to 4.5 amps is where most hobbyist run the 08 I do believe, also understand that removing the cans expose the dye to contaminants and can shorten lifespan, going to 3.75 amps is not a big deal in my opinion.
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