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Blue Katana, a 70 watt handheld project!

paul1598419

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How do you figure 14 3.9 ohm resistors in parallel would give you 2.66 ohms? :thinking:
 

paul1598419

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Well, 14 39 ohm resistors would get you to 2.786, but that isn't close enough. I don't see another way this could be a typo and still work.
 

Benm

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Oh, i just meant that as an example on how to get a low-resistance, high power resistor from jelly bean components. Since 39 is a preferred value in the E12 series i went with that, but you could also combine several 47 ohm resistors or a mixture if you are aiming for an exact value.

Using a parallel array of resistors is practical though: no need for specific components, and you will need the physical space to dissipate the heat regardless.
 

paul1598419

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I think a linear driver is a bad idea for running that much current. There has to be a buck that would work for this. Far less waste heat to worry about.
 

paul1598419

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I was talking about a single buck driver instead of a single linear one. Especially one made from a voltage regulator IC. The buck would have less waste heat to dispose of.
 

RedCowboy

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It's a 10 second duty cycle and 9 X 44's are going to make a ton of waste heat, the drivers waste heat is not an issue for a 10 second duty cycle of this type, but if he trusts the SXD drivers then go with those, but I don't know if I would use the 3S hobby packs, maybe just use high drain 18650's possibly 18 in 6 strings of 3.
 

RedCowboy

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I'm saving up used 44's that over a year or so of regular use are down to 75% output, so I will string a bunch together one day with a inexpensive linear and a couple of 24v cordless power tool packs and converge with 3 elements in a big cluster spot just for fun, I have even seen some 6w blues for 50 dollars, however a new 44 with driver, module, lens and you are talking about 125.00 each so it depends on what the user wants. I know 10 seconds goes by fast when having fun.

The 12 x 18650's I don't think will hold up very well powering 9 x nubm44's and the 3S hobby packs could be a problem for the 30.00 drivers, so like you say it's a balance.
 
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I'm just wondering why not using a heat sink fan, with a waste heat of 120w, just aluminum heat sink is not enough,and can use bank nubm44 8pcs,my country sell it 400usd,i think it is better
 

RedCowboy

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I think he want's a 10 second duty cycle and not a lot of excessive bulk, so everything only needs to strain for 10 second bursts, lead acid batteries and fans are ok for a laser on a cart, this is a short duty cycle HH
 

DTR

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I can see the utility in having a jig to set drivers on, but I would never run them through on a hot supply as that is the best way I know to kill one. I know it is a PITA, but setting your supply every time when I am setting up a driver has saved me countless times from really stupid errors because you can't be aware of everything going on all the time. It also works quite well when driving LDs to check the wavelengths when you have twenty or more to do.
Yea I have a bunch of videos somewhere of the testing I was going over with angelos basically using a driver with many starts via sessions of hot connect 9V or from zero the best way, fast loading and unloading hot and runs for longer durations up to thermal shut off then turning my supply to 12V and hot connecting with about a 20% kill rate. Best was I did get a pic of the input cap exploding on one. up. by hot connecting with 9V

Anway the biggest problem is the world I have to live in which is not the way I would do it but the way 90% of the people that buy units from me would if they used a variable power supply would by turning on their supply, setting the range and hot connecting. This is why I was trying to get a solution to death from loading or I guess now even unloading spikes which there was another link I posted that showed a loading surge near 40V as well as the one you saw with the disconnect one.

Anyway even if I put a warning not to hot load there still would be lots of people that would either miss it or have a fubar moment which really is the biggest issue with power supplies the process that is just not as simple as push a button for on/off.

Out of these learning events for new laserist there are always some that will just message saying the item they received does not work as that is usually the first thing that comes to mind when you buy non DIY stuff. Buy something and plug it in or put batteries in it, push the power button and if you get nothing it must have come broken right. So that is something if the driver can be made to deal with would be great.


I think a linear driver is a bad idea for running that much current. There has to be a buck that would work for this. Far less waste heat to worry about.
If a bunch of diodes in series, compared to using individual drivers, the loss or heat is divided by the number of diodes being driven, it isn't that much.
That was my first thought for this build. A High voltage linear and run them like they are in the projector if you can stack enough cells with the way you configure the unit. Also if thee is anyway possible I would always choose a 2 Li-Ion in series config over a 3 Li-ion in series config with the common buck drivers we use. You get full battery cycle with two and you are asking the drivers to work harder and make more heat while edging ever closer to the max input voltage of the driver plus if you go with some high drain cells like IMR's or something are we not working more toward the extremely low resistance we are thinking might be an issue with the 3S packs or even the variable power supplies that don't do enough to suppress these events and in most every build I have seen batteries are not variable so it is always hot loding them.

I will find those videos when I get some time. Been going at writing this between breaks for several hours today and on top of that when it rains it pours. Check out what I did now. Pretty sure I feel a bone chunk just floating around in there. Going out the door and dropped my ecig but in the attempt to catch it swinking around at full force of impact swunt my hand into this stupid metal ringer thing that is on my garage door. This was on Monday. Hurt but did not think much. Tuesday morning I woke and it was a giant lump that was about the size of a superball, now my entire hand is turning purple as of last night and if feel something hard and floating in there. Did not think it worth going for an X-ray as you cant really do much but my hand looking like an umpa lumpa I might have go and get it looked at if it keeps going this way. At the moment it has not put a huge crimp on working. I am a righty so most dexterous things like soldering are with my right and mostly just steading actions with the left. I can hold wire up to get soldered do light bending without pain but try to make a fist it starts to hurt some and try to squeeze and oh boy.:(



 
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Oh my God Jason, your hand looks very bad.
I suggest You a check in hospital, really!

So, my main problem is not the moneys for 9 drivers (I wish to use 9x 5.5A Blackbuck drivers new release from x-Wossee),
but the possible spikes and transient using the 3S LiPo pack.
Really, with these kind of cells I will save space, weight, money, and have all the amps that I need.
Surfing in internet I have found this tool:

https://www.ebay.it/itm/SPIKE-SUPPR...056738?hash=item3a870fb522:g:W8sAAOxy4t1Sem6H

Anyone know if this little toy can emiminate the unwanted spikes?
 
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RedCowboy

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OUCH, maybe put an ice pack on that hand to take the swelling down. LOL @ umpa lumpa

---edit---

I posted in lifetime17's sale thread about using a backwards G2 then a 3 element and how well it corrects the beam from the GBall diodes, so now I am again thinking about the blocks of 8 if we had some threaded sleeves made to press down around the GBall cans we could screw in the backwards G2 and a G7 or 3E and have 8 focusable beams in close proximity, with 2 blocks we would have 16 beams that could be fired into a large lens, maybe a large homemade beam expander of sorts...............I wonder what machine those nubm49 diodes come from, the block looks about right for this.

 

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RedCowboy

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I figured with 12 18650 cells in series the LM338 will hardly have to dissipate anything, actually with the sag 12 may not be enough.
 

DTR

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What I meant by the heat divided by the number of drivers might not have been fully understood by some, now that I'm reading what I wrote I'm not sure. I meant, for example, lets say you have 10 diodes with 10 drivers, and the heat loss is, for example, 5% in the driver, add the heat being lost per driver together and you get a sum of heat, now compare how much heat you are getting from a single LM338 driver, or two of them etc. which has a far lower efficiency, how much difference between them? I think the cost savings is worth it to use two or three less efficient drivers than 10 more efficient ones.

Of course, much depends upon how close the output voltage is to the supply voltage, if the two differ too much, now the heat being produced is huge. I.E. 30 volts input, 12 out... Nope! Don't do that. Sure, for the LM338, if enough heat sinking, it works, but the proper way to design it is to have your supply voltage closer to the output voltage needed so there is less power loss regulating the output. As long as you keep the dropout voltage consumed in mind along with other ohmic losses, should work great.
I figured with 12 18650 cells in series the LM338 will hardly have to dissipate anything, actually with the sag 12 may not be enough.
I was thinking at least two strands like the old A's had 4 strands of 6 in series. On these if you did say two strands of 5 diodes then say the 24V forward range. Add a volt for the dropout and you would want to do two strands of cells in series instead of all cells in one chain. To be near 25V when near full discharge needing to be recharged to get the most runtime. One factor to bear in mind the more you put in series then the larger the fully charged voltage to fully discharged voltage becomes and if you are able to get it near perfect then you are dropping near no waste heat at the very end of that cycle. So regardless of the number you end up with to make that math work right two parallel strands of cells in series would reduce the amount of waste heat at the fully charged voltage you get the doubled capacity so hopefully it will be about the same runtime compared to all cells in series where it would be twice the waste heat at the start.

So maybe two drivers separately driving each strand of diodes in series and in parallel on the input side connected to a two strands of cells in series. That was what I would think.

I don't know why you are not getting that x-ray'd asap!


I am 100% it is not a full fracture or break as when it started getting discolored I looked up some info and played doctor a bit. I bent my wrist putting pressure on my thumb as directed which it said there would be great pain to the point you could not do it and that is not an issue. Any pain is when force them into a ball. I am nearly sure a small part off the rounded top of the scaphoid bone chipped off. There really is not anything they would do in the right now for that. If over time beyond the diminishing effects of the trama pain persists they can go in and remove it unless determined to be large enough or placement is needed for the bone to have proper structural integrity they can go and screw it down to heal and reform to each other.

The only thing that I feel would be an issue if there is some sore of infection of scaphoid that is causing the look.

Really I just don't have time, Too much to get done beofore the weekend specially a couple large orders needing to get to DHL today which not out by Friday can be the difference of it landing sometime next week or the following.
Anyway I think is is all just blood in the tissues and the swelling but when I finish tonight I will see if better or worse and if worse I will make some moves. It just was strange the first day really nothing but a reminder of pain when I made a fist to the lump a day later to the day or two it started bloating and looking all discolored.

Need to find the picture of the time I was building a coin mod for one of the old laser hosts and put the power drill most the way into my hand with a nice shrpt bit. Had a good pic I posted up then if anyone remembers.
 
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paul1598419

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Geess, Jordan. You should seek medical attention for your hand ASAP! You could very well have an infection taking place in there. Even if you never broke the skin there are microbes in tissues that can become the source of a really bad infection. Also, if you broke bone it needs to be set right away before it becomes something even more complicated because you waited. I broke the distal end of my left radius ten years ago and it ended with me losing most of the use in that hand even though I got medical attention promptly. I hope you can get into a hand specialist or at least go to an emergency room, not an urgent care. That could very well require surgery. Sorry for going on and on about this.
 
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