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

tsteele93 · Jun 12, 2012

Surely there is someone with more knowledge of how to use a scope to test a driver who has one of these $10 drivers. I can send Le Quack a driver in a package soon. But I can't believe there isn't anyone with a scope and one of these drivers.

I'm sure my inexperience is causing some confusion and I may be doing something wrong but I am trying to be very descriptive and cover all the details. Plus I was hoping the scope would show us enough info for it to "make sense."

It does look like I am getting a startup spike for sure, but I'm not sure what the other noise is or why the freq looks odd. I'd shoot for user error before jumping to any wild theories though.

The driver seems to function properly. We are getting the correct mV across the test load resistor. Without a scope there is no way to see that startup spike.

Also, someone asked about the caps. I'm pretty sure Moh used the 10uF mouser caps.

I could try removing them with a hot air gun and putting on 0805 22uF 16v caps and see what it looks like.

Tomorrow.

Wolfman29 · Jun 12, 2012

I would suggest that, Tom (regarding the caps). Then we can do a comparison shot.

tsteele93 · Jun 12, 2012

Le Quack said:
The mosfet doesn't care, and shouldn't care what happens after it, because it doesn't.

If only they wrote textbooks like this!

The best part is that I actually understood it!

tsteele93 · Jun 12, 2012

Wolfman29 said:
I would suggest that, Tom (regarding the caps). Then we can do a comparison shot.

I can also try scoping across the LD+ and LD- if that would be better and won't hurt the test load. From what I have read on scopes, it is pretty hard to hurt them so I don't think I can damage it with a 4v Li-ion hooked to a 1/2 amp driver.

Wolfman29 · Jun 12, 2012

Eh... scoping across the output of the driver won't really help. As we know, the Vf of laser diodes change very little with high current changes, so it's likely the spike will be more obvious if you read it across a resistor.

tsteele93 · Jun 12, 2012

Wolfman29 said:
Eh... scoping across the output of the driver won't really help. As we know, the Vf of laser diodes change very little with high current changes, so it's likely the spike will be more obvious if you read it across a resistor.

Ok, I will try changing caps then.

I also have a couple of MOHs benboosts down around 190mA (I have no idea why I ordered those) that I can test as well. Maybe the reading will make sense if we can see what they show vs the 190mA output and what the scope shows vs the 480mA output driver. If that made any sense.

So tomorrow I will try putting on better caps. I have a few really good 0805 Kemets that are 10% 22uF 16V x7r rated and we will see what they look like on the same scope with the same settings.

That's GOTTA show us something. Hopefully...

One tangent note, I'm not seeing much heat at all with .480A on this driver or on the test load. Makes me think that heat sinking the driver is a waste at lower currents. I was trying to heat sink a ~.500A 12x build earlier and it was making the logistics much harder. Playing with the driver on a load has me convinced that it is a waste of time and effort to do any fancy sinking at this current on a Benboost. Maybe up around .750 or 1A - but not at 1/2A.

rhd · Jun 12, 2012

tsteele93 said:
One tangent note, I'm not seeing much heat at all with .480A on this driver or on the test load. Makes me think that heat sinking the driver is a waste at lower currents. I was trying to heat sink a ~.500A 12x build earlier and it was making the logistics much harder. Playing with the driver on a load has me convinced that it is a waste of time and effort to do any fancy sinking at this current on a Benboost. Maybe up around .750 or 1A - but not at 1/2A.

Ditto with my testing today. I had it running on and off for ~20 minutes or so throughout the process, and there wasn't much of a heat issue.

tsteele93 said:
So tomorrow I will try putting on better caps. I have a few really good 0805 Kemets that are 10% 22uF 16V x7r rated and we will see what they look like on the same scope with the same settings.

That's GOTTA show us something. Hopefully...

Despite the fact that we're all expecting (hoping) the caps to be our saving grace, I'm not convinced that the difference between 10uF and 22uF caps could account for the dramatic difference between what TSteele and I observed with are respective versions of the driver. I just can't imagine 10uF vs 22uF accounting for ~450 mV vs ~40mV of ripple (or whatever label you want to give it).

It strikes me that that difference must be explained by:
1) A problem with one of the components.
2) A problem with the construction / reflowing.
3) A problem with the additional MOSFET
4) User error (mine or TSteele's)
5) Scope error (or rather, "my DSO Nano isn't a very good scope" syndrome)

But, we'll know soon

foulmist · Jun 12, 2012

Again I would ask Tom to switch to AC coupling and then see what's the ripple. As you know the ripple is jumping high and low and it should be easier to read it with ac coupling.

I think that will give more accurate results as you will be able to see only the ripple!

Kizdawg · Jun 12, 2012

Have you built the boards yet Toma?

foulmist · Jun 12, 2012

Kizdawg said:
Have you built the boards yet Toma?

No man, I don't have the inductor and the caps that are used with this design, even if I put some they won't match the design here and it won't be the results we are looking at.

Kizdawg · Jun 12, 2012

Geese! Why didnt you ask me to throw them in??? I just assumed ya had components..

And no I still think part of the problem is that RHD is using a different design than Tsteele too. and mine are the other 2 designs.. round and OVP..

foulmist · Jun 12, 2012

Kizdawg said:
Geese! Why didnt you ask me to throw them in??? I just assumed ya had components..

And no I still think part of the problem is that RHD is using a different design than Tsteele too. and mine are the other 2 designs.. round and OVP..

I didn't know you had spares

and I didn't wanna bother you

damn...

anyway I would suggest the AC coupling to Tom

Kizdawg · Jun 12, 2012

my first digikey order was over 200$ and I didnt buy the IC's there.. just saw that a little quantity on the order and the parts were allmost half price. so thaught it was a good thing at the time.. then baught more of the smaller round inductors to fit the round boards better then baught the 22uf caps and some resistors for lower currents.. I have stuff here I will never use... :tired: If ya want me to send ya out some components I can do that. I just dont have the 22uf caps for the OVP boards.. but I bet the smaller ones could be hand soldered on them pads..

Kizdawg · Jun 12, 2012

Oh And I built a working Laser tonight! 805T 100ma mogasm linear in a grey Unique fire A10-B... and it works!! I was happy W00t! W00t!

tsteele93 · Jun 12, 2012

foulmist said:
Again I would ask Tom to switch to AC coupling and then see what's the ripple. As you know the ripple is jumping high and low and it should be easier to read it with ac coupling.

I think that will give more accurate results as you will be able to see only the ripple!

I missed that, I will try it.

tsteele93 · Jun 12, 2012

Ok, I will be uploading in a few. I was able to successfully remove the caps and put on new ones and plug it up and get .480 amps again. But the scope readings seem quite different. Let me upload.

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

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