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FrozenGate by Avery

LM317 Driver question

jib77 said:
For a 3A continuous current rectifier I use a OnSemi 1N5401G. Put a cap on the input otherwise the LD1085V will not be stable(datasheet recommends 10uF, but another 47uF should be fine). Your resistors will need to handle 3.75W, make sure they are rated 2W each so you get a total 4W of available power dissipation.
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Personally I like to use resistors with a PD~ 2x more than my actual PD but that is just me hating when things get hot
 





Ok thanks I have come to a conclusion that I am going to stick to my 1st plan with one LM317 as that goes up to 1.5A. I will just power it up t 1.5a and then have an adjustable pot so I can change it when I like. This way it will be simple :) I will just get a few resistors that will equal 0.8ohms. Do you think the origional idea is better as I don't need a 3a regulator if I am putting1.5A through. If I use. Lm317 it will reach 1.5A but I will add a big heat sink.

Does ths seem like a better idea?
Do you think I should use just 2x 186500 batteries which gives 7.4v?


P.S sorry for any spelling mistakes I wrote this on my
iPod
 
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I think 7.4 will be cutting it close the lm317 needs ~2.5 + Vdiode and the 445 at that amperage are about 5V. Personally I would not run the LM317 at 1.5A but I just hate running things right at their limit. When I learned design I was always taught to leave a margin. You could always run 2 lm317s in parallel at 750ma each.
 
Personally I would not run the LM317 at 1.5A but I just hate running things right at their limit.
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If it is designed for a limit of 1.5A it almost 99.9% certainly was designed to be able
to run AT that limit, and has a built in safety margin. Just think about it...
Otherwise it would have to be rated at, like, 1.4A... ;)
 
itsmei said:
2xcapacitor of 10hm each in parallel to get me 0.5ohm, i will use more than 2 watt input.
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cat_wtf-12880.png


I don't know where to begin, so I won't. :undecided:
 
Spam /\ ....

Anyway I am just going to run at 7.4 v and 1.5a with a few resistors to cope with 1.5A. Anyone suggest any safety glasses I think that dragon lasers glasses are good. What do you think?
 
anselm said:
If it is designed for a limit of 1.5A it almost 99.9% certainly was designed to be able
to run AT that limit, and has a built in safety margin. Just think about it...
Otherwise it would have to be rated at, like, 1.4A... ;)
Click to expand...

Yea but it is 1.5A at a certain PD remember PD of the LM317 is ~ (Vin - Vout) * I so with a higher Vin it may not be able to support the thermal load at 1.5A Also as it approaches its current limit the Voltage dropout increases a bit requiring a higher Vin. But in the end you should be ok because it is a guaranteed 1.5A and a typical of 2.2

The dragon glasses are good. Also good luck with 7.4V I still think it is a bit too low.
 
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Ahh ok so you recommend 3x 18650 batteries to give me 12.1 v, will this not get things very hot. I am having a big heat sink but will this be enough?
I will get 2 pairs of glasses from dragon lasers.
 
itsmei said:
Ahh ok so you recommend 3x 18650 batteries to give me 12.1 v, will this not get things very hot. I am having a big heat sink but will this be enough?
I will get 2 pairs of glasses from dragon lasers.
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Try 2 but you may not get the current out you want. 3x at 3.7V for 11.1 should also give you a much longer run time. A decent heat sink with a good thermal pad or grease should be good.
 
/\ it was a typo....

Thanks for your help everyone! I will post pics when I get it!
 
Well I gotta say, I've been happy so far running only off 2x1850, as you can see in my
signature, bottom link.
Sure, after a while of running at full power, voltage sags enough that current
starts to decrease.
When both batteries are down to 3V, the diode doesn't even lase anymore.
 
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So you think that I should use 2x 18650 batteries. What mA and what driver do you power the diode?
 
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