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

[tsteele93]

Good to see you pop in around these here parts...

 

[Kizdawg]

Yep knew the mention of P0T would get your attention.. BC Life eh! Any chance your doing the easy LPM's???

Even an eagle and parts list?

And cant we make this potable and / or fixed? Never hurts to satisfy both parties and RHD I dont have the funds to keep buying and wasting IC's because I can make them I have a pile of drivers here I will probably never use unless I get desperate and remove the resistors to add new ones.. Oh and BTW There is a sale on these IC's at Newark. $2.55 for 1-24, $2.33 for 25-99, $2.18 for 100-249 CAD.http://canada.newark.com/jsp/search/productdetail.jsp?sku=55R3975

 

[Kizdawg]

Bah! :tired:

I really would like to see a pot I dont care if RHD is concerned about it. We are all adults here... His way is too FIXED for me. I am FLEXABLE.. hehe.. What diodes were these intended for anyway's? Eh I made some and am happy First reflow JOB!.. one of my favorite blue's is running on one. 9mm 445 @ 760ma with it's own lense. I just cant help expanding my knowledge Back in a post 500 or so ago I said if these max at 1200 with heatsinking we need to do something else and he apparently dual'd some 760's or 800's I dont recall but I asked him if I could parallel 3 and he sait why 3 when 2 work fine so I do think there is something more to this. I have tested 23. 24 is Bens and I have 1 IC left #22 hit the floor and was never found. Omar the carpet God strikes again!

Kiz

 

[benmwv]

Eeek, what has become of this.... POTs ? Noooooo! Oh well, I guess some people like variability. I like the security of fixed resistors. But I guess if you're not reflowing your own, but rather buying them, then fixed resistors might be frustrating.

Ben: Not AWOL, just making myself more rare around these parts. Don't have as much time these days.

Today I did manage to squeeze in an afternoon of reflowing some of the other driver designs that have been lingering in my Eagle folder for the last two months.

Ha we were just messing with you

I think I'll revisit the pot later when we are sure the caps issue is worked out. Did you see that thread about the 22uf caps actually being mislabeled 2.2uf?

You would happen to have made that one driver we were working on a couple weeks back? You know, that round one? Definitely send me an email about the results! You've got me all excited now

 

[tsteele93]

I am working on a driver and using some 0603 resistors that have to be hand soldered. I am pretty sure I get about one out of three on the board and the other two end up in the carpet.

My carpet has a resistance of several thousand ohms! :crackup:

Small parts are a bear to work with!!!

 

[Kizdawg]

LMAO.. that's a good one!..

Just a note on the pot I just dont understand the reason why pot's are disliked so much I just cant wrap my head arround it. for an example my 3x760ma drivers which put out 2.4-2.5A is just not what I wanted or expected so now I have to either sell them as 760ma drivers or I have to remove the resistors and try again with a set seting them lower. With a pot all I would be doing now it turning them down a bit and I would be done. not to mention the reason I didnt thermal epoxy them to the saik heatsink was because I wasnt sure how they would perform so saved me from prying them off the heatsink too. and can you imagine having to try to remove resistors and puting on new ones after they have been epoxied! Yikes! I dont even know if it is possible. So from my perspecive with a pot I would have 20 or so drivers I could use for anything instead of a bunch I probably will never use now.

 

[rhd]

Ha we were just messing with you

I think I'll revisit the pot later when we are sure the caps issue is worked out. Did you see that thread about the 22uf caps actually being mislabeled 2.2uf?

You would happen to have made that one driver we were working on a couple weeks back? You know, that round one? Definitely send me an email about the results! You've got me all excited now

No, I didn't. I was going to do that through Dorkbot, but then he added this new system that doesn't allow combination of orders (for shipping purposes). So basically, to order 3 board designs, with the $15 shipping option to Canada, I would have had to pay $45 in shipping, and then have him manually refund me the $30. In terms of complexity, I just wasn't down with dancing that silly jig and having money taken off my CC, and then tossed back on. Plus, the little panels I get fabbed every few months really suck for circular designs, because I have to cut them myself. So, no round 2A boost drivers this time around

In terms of the 22uF being labelled 2.2uF, I'm not entirely shocked. A lot of driver designs use capacitance of ~10uF (maybe two of them) in parallel with a 0.1uF ceramic. That's the approach I took with one of the driver designs I reflowed yesterday. A large 100uF tantalum, a 22uF ceramic, and a 0.1uF ceramic.

Kizdawg: In terms of just "paralleling more", I know that nobody likes to hear the advice that they shouldn't do something....maybe you *don't care* about my input, but I wasn't just shooting down the idea for fun (and heck, why ask if you don't want to hear the answer?).

I've always believed that people need to take the time to understand how a driver works, before using it in their build. That's part of the reason that I've always strayed away from using other people's drivers, when they're all protective and secretive about how those drivers work. In this case, it's important to understand the mechanism of paralleling and Open Boost driver, before just deciding that it's okay to parallel 3 instead of 2.

When you parallel these drivers, you're actually paralleling their current set resistors. As an illustrative aid, you can trace out the circuit on paper, and then parallel each of the four contact points with a second circuit, to see what I mean.

The formula for parallel resistance is:
R = 1 / ( (1 / R1) + (1 / R2) .... etc )

So imagine that you're deciding to parallel three of these drivers set with 0.3 ohm resistors, to produce 633 mA each when used on their own. Your objective would presumably be to achieve 1.9 A when the three drivers were paralleled. What happens when you parallel them? The set resistance that *each driver sees* when used in parallel is 0.1 ohm.

Why does this matter? Because it destroys the notion that each driver is limited to contributing 633mA. In reality, each driver thinks it is trying to regulate to the full 1.9A. But the fact that the other driver(s) is/are contributing to the chore means that each driver doesn't in practice have to actually be responsible for 1.9A.

The challenge, is that they're not intelligent enough to know this, and they're not necessarily going to have the same tolerances across the three drivers. The fact that two in parallel work, is fantastic. Some people who had experimented with this IC in alternate circuit designs before us, weren't able to get them working in parallel. Frankly, a little bit of luck was on our side, but that doesn't mean that the luck can scale. These aren't simple batteries, we can't presume that "paralleling more of them together" will just continuously improve their amperage capabilities. In fact, quite to the contrary, I would expect reliability to fall greatly. These are very high frequency switching regulators, and it's not the case that you can just toss 10 of them together, set for 800 mA, and get a working reliable 8A driver out of it, etc.

 

[tsteele93]

Just a note on the pot I just dont understand the reason why pot's are disliked so much I just cant wrap my head arround it.

I'm new here and have asked the same questions - best I can tell it comes from the old-school days of people buying green laser pointers, opening them up and turning a pot until they got higher power - or fried the diode.

It got a bad rap. And once laser makers started building lasers closer to their limits, it didn't work most of the time anyway because the laser was already at its limit and turning the pot just fried it immediately.

So pots got a bad name and now they are frowned upon.

I also think that most of the pots that people put on drivers are crappy pots. I haven't explored this yet, but I'm guessing that GOOD adjustable pots are expensive. So you run into a problem...

Do you spend a lot of your driver budget on an expensive adjustable pot that MIGHT get set once and never changed? Or do you buy a cheap one that might fail and make your driver look crappy? Or do you put a fixed resistor in there and know exactly what it is going to do?

I think most designers go for the fixed resistor.

 

[rhd]

I'm new here and have asked the same questions - best I can tell it comes from the old-school days of people buying green laser pointers, opening them up and turning a pot until they got higher power - or fried the diode.

It got a bad rap. And once laser makers started building lasers closer to their limits, it didn't work most of the time anyway because the laser was already at its limit and turning the pot just fried it immediately.

So pots got a bad name and now they are frowned upon.

I also think that most of the pots that people put on drivers are crappy pots. I haven't explored this yet, but I'm guessing that GOOD adjustable pots are expensive. So you run into a problem...

Do you spend a lot of your driver budget on an expensive adjustable pot that MIGHT get set once and never changed? Or do you buy a cheap one that might fail and make your driver look crappy? Or do you put a fixed resistor in there and know exactly what it is going to do?

I think most designers go for the fixed resistor.

(most of) what he said ^.

Though I personally couldn't care less about the pot modding history. I think it's a goofy practice, but I wouldn't make a present day driver decision based on some unrelated history.

I have a number of issues with pots:

1) They're an additional point of design failure. Potentially, they may even represent two or three additional points of failure if you need to use an additional IC and resistor to scale the set resistance on account of pots being much higher resistance than most set resistors.

2) They're an additional point of build failure. They are more prone to getting knocked around, jiggled out of place, intentionally changed, and can be less resistant to general environmental heat than set resistors. They can also get nudged during the build process itself, particularly with a tight/small project.

3) They are often less precise. Particularly with the single turn set resistors often found in small drivers, your ability to set a precise current is often less granular than it would be with a fixed resistor. With any mechanical device, there is often a starting force required to make an adjustment that will cause you to "jump" over the very fine/small movement increments that you might need in order to be able to get a current right on target.

4) They are more prone to errors arising from test load usage. This can be a very real issue for a lot of users here. Someone has pegged pots as being for "beginners" and fixed resistors being for "pros". That's totally backwards (or rather an inapplicable attribution really). With a pot, you need a test load to set the current. What happens if you select too many diodes on your test load? This thread has already illustrated the fact that people make a lot of mistakes in their test load usage. Well, with a higher simulated Vf than your actual diode, you may select a pot resistance that produces a current reading that is artificially limited by your driver's struggle to reach the Vf you've set on your test load. Feeling comfortable in your configuration, you'd then connect your driver to the real diode, with a lower Vf. Now, the driver has no trouble reaching the Vf of your diode, and it is able to realize the full current that you've (unknowingly) set your driver to deliver. Poof, your diode is dead. With fixed resistors, you know what you're getting, and really don't even need to own a test load if you trust the driver-maker.

Kizdawg: Missed your EasyLPM comment. Actually, I haven't made the Arduino compatible model in a while, but I HAVE just reflowed a basic Ophir driver, with 5V output for LED readouts. I have extra PCBs if you want one.

 

[tsteele93]

In terms of the 22uF being labelled 2.2uF, I'm not entirely shocked. A lot of driver designs use capacitance of ~10uF (maybe two of them) in parallel with a 0.1uF ceramic. That's the approach I took with one of the driver designs I reflowed yesterday. A large 100uF tantalum, a 22uF ceramic, and a 0.1uF ceramic.

Other way around. Those 22uF's that I ordered from ALLIED ELECTRONICS turned out to be 2.2uF's

I'm still waiting for them to give me an RMA - apparently Rhonda (my salesperson) is out sick.

What REALLY disturbs me is that they don't seem too concerned that it happened and they haven't rushed to get me an RMA and they haven't even changed the incorrect listing on their site so you could still go and order the incorrect caps.

I realize that I am only a hobbyist, but I assume major companies order from sites like this too and it could screw up something important for someone.

How can you run a site like that sloppily and not get hammered for it?

I know it made me look stupid, but I naively assumed Allied would be like Newark or Digikey or Future Electronics or Mouser and that they would be super reliable in sending out small SMD devices properly labeled!

but I HAVE just reflowed a basic Ophir driver, with 5V output for LED readouts. I have extra PCBs if you want one.

I would like one - I will (of course) pay for it. PM incoming.

 

[rhd]

Let me pop this one onto an Ophir, and make sure it works. This is roughly my 10th try at this, and each time something isn't quite perfect. That said, this is basically a PCB incarnation of the soldered-together design I'm already using, so it should be my final revision.

It's using a Micrel linear IC that I've never used before though (but not for anything crucial, so it should be fine).

 

[benmwv]

No, I didn't. I was going to do that through Dorkbot, but then he added this new system that doesn't allow combination of orders (for shipping purposes). So basically, to order 3 board designs, with the $15 shipping option to Canada, I would have had to pay $45 in shipping, and then have him manually refund me the $30. In terms of complexity, I just wasn't down with dancing that silly jig and having money taken off my CC, and then tossed back on. Plus, the little panels I get fabbed every few months really suck for circular designs, because I have to cut them myself. So, no round 2A boost drivers this time around

In terms of the 22uF being labelled 2.2uF, I'm not entirely shocked. A lot of driver designs use capacitance of ~10uF (maybe two of them) in parallel with a 0.1uF ceramic. That's the approach I took with one of the driver designs I reflowed yesterday. A large 100uF tantalum, a 22uF ceramic, and a 0.1uF ceramic.

Kizdawg: In terms of just "paralleling more", I know that nobody likes to hear the advice that they shouldn't do something....maybe you *don't care* about my input, but I wasn't just shooting down the idea for fun (and heck, why ask if you don't want to hear the answer?).

I've always believed that people need to take the time to understand how a driver works, before using it in their build. That's part of the reason that I've always strayed away from using other people's drivers, when they're all protective and secretive about how those drivers work. In this case, it's important to understand the mechanism of paralleling and Open Boost driver, before just deciding that it's okay to parallel 3 instead of 2.

When you parallel these drivers, you're actually paralleling their current set resistors. As an illustrative aid, you can trace out the circuit on paper, and then parallel each of the four contact points with a second circuit, to see what I mean.

The formula for parallel resistance is:
R = 1 / ( (1 / R1) + (1 / R2) .... etc )

So imagine that you're deciding to parallel three of these drivers set with 0.3 ohm resistors, to produce 633 mA each when used on their own. Your objective would presumably be to achieve 1.9 A when the three drivers were paralleled. What happens when you parallel them? The set resistance that *each driver sees* when used in parallel is 0.1 ohm.

Why does this matter? Because it destroys the notion that each driver is limited to contributing 633mA. In reality, each driver thinks it is trying to regulate to the full 1.9A. But the fact that the other driver(s) is/are contributing to the chore means that each driver doesn't in practice have to actually be responsible for 1.9A.

The challenge, is that they're not intelligent enough to know this, and they're not necessarily going to have the same tolerances across the three drivers. The fact that two in parallel work, is fantastic. Some people who had experimented with this IC in alternate circuit designs before us, weren't able to get them working in parallel. Frankly, a little bit of luck was on our side, but that doesn't mean that the luck can scale. These aren't simple batteries, we can't presume that "paralleling more of them together" will just continuously improve their amperage capabilities. In fact, quite to the contrary, I would expect reliability to fall greatly. These are very high frequency switching regulators, and it's not the case that you can just toss 10 of them together, set for 800 mA, and get a working reliable 8A driver out of it, etc.

Man I was really hoping to see that one running! My boards should be here soon. I waited until I had a few more boards ready and ordered them all at once.

You can still email him your order since he doesn't have all the bugs worked out yet. I didn't realize the shipping to Canada was so much! I would have thought maybe $3 or so.

That llp3x3 version I posted a page back was designed for two 22uf and 0.1uf, though they aren't directly in paralell. I was going for 22uf input, 22uf LD+ to GND, 0.1uf LD+ to LD-.



RE pots, I don't think they get a bad rep from green lasers and pot modding but maybe I'm wrong?

Here's my list of drawbacks for having a pot:

-may not be able to figure out how to add a pot
-adds complexity to the reflow
-more expensive
-most pots small enough to be on a driver are crap
-doesn't have the security of fixed resistor

There are good multi turn smd pots but they are a bit large and cost ~$4 each.

 

[rhd]

Oh I'm an idiot. I reversed tantalum caps. Forgot that their markings are opposite. Gotta grab some more parts before I can re-test this Ophir driver.

 

[Kizdawg]

Fair enough I see the light! From a designers POV I can see how they could be problematic and more expensive. I dont know enough about how to do it to comment about designing it. If it meant another ic etc like I am hearing then I guess I can live without it ..

RHD you know I allway's like hearing your comments. Just a poke to get you going again. :tinfoil: And you made alot of good points on why not which was exactly what I needed to hear. Yes I would be very interested in a board for the ophir. I really want to get it boxed up and protected.

As far as paralleling 3 goes I was willing to risk the testing of them this way but if I understand you right at my 2.4A output you were saying that it may have been possible that 2 of the drivers were outputing more than the 760ma and one may only be outputing less because even though the set resistor for the individual board is set for 760 paralleling them combines there resistance making it possible for a individual driver to output more than the 760ma? Meaning in the end one or two drivers could be working alot harder than the other/s. To prove that we would have to somehow measure the current of each individual driver while they were operating in parallel. Even if they were I heard talk about ading resistance on the output to balance the output currents of the paralleled drivers Not too shure what that involves but if it works that may be a solution.

Ben I think that the board your working on with more copper under the IC should help alot I think alot of issues here are due to excess heat so I would love to test that board out when you get your design finished.

I have just been reading the 2.2uf caps thing and I got mine from allied too so I need to find out what I have.. BTW They bent me over on shipping too was allmost 3 times the price from allied than from newark or digi.

 

[tsteele93]

RHD, I would be happy to order PCB's on Dorkbot (OSH Park) and send them to you using cheap 1st class mail. I think it only costs me $3 for first class to Canada.

It is odd that it would be cheaper that way, but OSH Park is free shipping to US, so the only expense would be for me to ship to you - so I could ship for $3.

I'd be happy to help out if you need it.

-Tom

 

[Kizdawg]

Dorkbox didnt charge me much for shipping. My order of 27 of each round and ovp was 32.79$ And really it didnt take long to get them maybe becuse I got in at the end of a pannel and just filled it up.

Tsteele do you have any mofset's you want to sell Digi is out of them and newark doesnt stock them either. I'm down to 2!