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FREE DIY open source BOOST driver!!! Tested & working!!

tsteele93

tsteele93

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foulmist said:
I suggest everyone replace the caps with 22uF X5R or 22uF X7R.
I think the original part list and schematic should be updated too.
Click to expand...

I am a BIG fan of good heat property components, but just to try and keep very focused on the specific issue at hand, I don't think heat rating was the issue here since the diodes have been dying on startup.

I definitely think 10uF vs 22uF is likely to be more important than X5R or X7R in this particular case, and the possibility that MAYBE some of them were eBay caps of unknown pedigree could be an issue as well.

It would be nice if RE, Cilegray and Moh could chime in on what caps they were using.

Also, LeQuack, just to confirm, but I am pretty sure you used the Kemet 22uF/16v/X7R 0805 caps that I sent you on the 12x that you have, correct? And that one is fine?

It is definitely LOOKING like the caps are the issue, but it would be more certain if we knew which caps were on each driver that has experienced issues and which caps are on the drivers that are on 12x or single mode builds that are still working.

Also whether anyone was using Ebay caps that might be junk, or just name brand caps that don't have enough capacitance to do the job correctly.

If it turns out that 10uF is the issue then the OP should be changed as I don't think it is reasonable to expect someone to see a nicely laid out parts list in the OP and somehow know that they should skim 30+ pages and ~a thousand posts to find out that it might be better to use 22uF caps.
 





Hiemal

Hiemal

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tsteele93 said:
I am a BIG fan of good heat property components, but just to try and keep very focused on the specific issue at hand, I don't think heat rating was the issue here since the diodes have been dying on startup.

I definitely think 10uF vs 22uF is likely to be more important than X5R or X7R in this particular case, and the possibility that MAYBE some of them were eBay caps of unknown pedigree could be an issue as well.

It would be nice if RE, Cilegray and Moh could chime in on what caps they were using.

Also, LeQuack, just to confirm, but I am pretty sure you used the Kemet 22uF/16v/X7R 0805 caps that I sent you on the 12x that you have, correct? And that one is fine?

It is definitely LOOKING like the caps are the issue, but it would be more certain if we knew which caps were on each driver that has experienced issues and which caps are on the drivers that are on 12x or single mode builds that are still working.

Also whether anyone was using Ebay caps that might be junk, or just name brand caps that don't have enough capacitance to do the job correctly.

If it turns out that 10uF is the issue then the OP should be changed as I don't think it is reasonable to expect someone to see a nicely laid out parts list in the OP and somehow know that they should skim 30+ pages and ~a thousand posts to find out that it might be better to use 22uF caps.
Click to expand...

Right, I only used the ones you gave me in the driver, and it works fine. No problems here with my benboost!

Maybe we ought to have the capacitors in question sent to someone for indepth testing, to see what their capacitance really is, what their voltage ratings are, etc.
 
Kizdawg

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When I get my new caps I will try another phr with a new board Hopefully by the weekend.

My 10Uf caps came from digikey so there source isnt in q.

I'm just hoping that the caps are the problem I had. And I can put this to rest..
 
rhd

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Jerry: Where my mind was going with that, was the input cap might have been charged prior to reflowing it to the board, and perhaps it actually then discharged into the IC at time of board manufacture, damaging it.

I don't believe that a likely scenario. It's just what I was trying to brainstorm around for a bit yesterday.

If there actually is a problem, and I'm not convinced that there is, it looks like it's probably the use of 10uF instead of 22uF caps.
 
benmwv

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Whoa guy this really exploded! I haven't been on for a couple days so I just read all these new posts.

As far as I know, Moh used mouser caps on his boards. Im pretty sure he had already quit making them before he even got the eBay caps. He may have used the eBay caps on his very last batch he sold to Clif (this was after he shut everything down), I'm not sure.

About the 2 output caps, as rhd said the one parallel to the LD was just added because we felt like it. If it wasn't there people surely would have complained. But they are both equally important if you ask me. They are basically in parallel (only separated by a very low value resistor) so it shouldn't make a huge difference if you beef up one and not the other. I think the best route is to use 22uf for both of them.

I'll add something to the OP.
 
foulmist

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benmwv said:
They are basically in parallel (only separated by a very low value resistor) so it shouldn't make a huge difference if you beef up one and not the other. I think the best route is to use 22uf for both of them.
Click to expand...

@ tsteele93 : EDITED! :D I am going to bed now damn I haven't slept well in 5 days. :D

Actually both are very important and it will make a huge difference if you removed either of them. They aren't in parallel exactly and that sense resistor separating them is not something to be overlooked.

V+ / GND caps are doing most of the job in decreasing the output ripple current. The extra cap between the V+/FB (across the laser diode) is actually decreasing the current ripple even further but without the V+/GND caps it wouldn't do much.

So they are both important but if you were to remove one it should be the one across the LD not the real output caps. But it's better to stay there and yes 22uF would be the best choice for it too.
 
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tsteele93

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You might want to check over that Tom, I couldn't quite understand the end of the first paragraph. Looks like it got cut and pasted or autocorrected or something.

:)
 
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Kizdawg

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So I was just wondering if the current calculation is correct or if it is a problem with my multimeter or testload but every driver I have made sits at a little more that what it is supposed to. I got my new 22uf caps yesterday and made a couple new drivers one with a 1.8ohm resistor the driver should sit at 105ma but it is more like 168ma on a 4.02v 18650. I'm not sure why my readings are wrong. but in every case the drivers allway's puts out more than they are supposed to. Moh's 667ma drivers I test even put out 740ma.

Could this just be my cheap 20$ ebay multimeter giving me troubles? I know when the battery light came on on the mm it was giving way higher readings. I think I noticed a 667ma driver puting out 1200ma and found that it was the battery in the mm.

I'm not sure what is going on for sure.. could be the mm or testload(6diode flaminpyro 3A copper) I know tom said to try more diodes but when I run that in my head it just means there will be more voltage drop (simulating that the diode would use more voltage than 6diodes) I dont know. I throw a regular 3v li ion on this and I get a steady 113ma so the driver seems to output different currents at different input V.

Confused Kizdawg
 
Hiemal

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Well, 6 diodes would mean a 4.2 volt drop...

Add more diodes to the test load. Otherwise your boost driver will be struggling to do what it's made to do; boost voltage!
 
Wolfman29

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Jared, you have much more patience than I! I have gotten so frustrated by this same question getting asked over and over again lately... =p

All the same, yes, I typically use 7 or even 8 diodes for BR diodes.
 
Wolfman29

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It's not you in particular. It's just a seeming lack in the workings of a test load amongst many of the newer members lately.
 
Kizdawg

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Yeah and I thaught I was getting a latest and greatest! lol It sure looks good though.. I'm going to come up with a mod for it to add 4 more diodes I guess..
 
rhd

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You guys should probably talk to FP before presuming that his test load isn't adequate in number of diodes. Not all does have the same Vf characteristics, just like not all LDs have the same Vf.

For example, you can find diodes that will drop 2V at even low currents, if that's what you want. So it's not just an automatic given that his diodes drop 0.7V each.
 
rhd

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Wolfman29 said:
Yeah - I'm just talking about 1N4001 variety diodes =p
Click to expand...

You made a really good point though. Test loads are not complex, but they're so often completely incorrectly used, or used where they aren't necessary. Or people do the math forgetting to take the IV slope of the diodes into account. Or people forget to take ohms law into account when calculating the drop across the resistor (which is particularly strange since we rely upon that same principal for the ability to actually measure current in voltage mode on our DMMs). Or sometimes people just fail at the multiplication.

And it's a great example of the frustration that has come up a few times already. IE, people looking to suggest that there's something wrong with the driver, when really it's just (in this case really basic) user error.
 
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