Fusion drivers revisited. UPGRADE!

[Kenom]

OK I'm not going to explain the fusion driver fiasco to those that don't know about it. I'm not into drama. What I will say, is that the driver itself, is not a bad driver, the board just had a few problems.. Like silkscreening that was backwards so that you soldered a component on wrong if you followed what the label said. Now if you know what is wrong with the silkscreen, you can obviously work around that. Well, another of the complaints was there were through the hole components and smt components. Some of the components were hard to solder from the one side. Well today, I got my drivers from Jayrob, and (nice free knife jay) had ordered all the components needed for this minus obviously the board. However this time, all the components were SMT. So I proceeded to assemble this badboy.

Now let me point out. I know next to nothing about circuit design or even how to trouble shoot a circuit. You can ask lava. He's spent hours talking me through how to fix my mistakes. So I ordered one component wrong. The LM385. The one for the driver is supposed to be 1.2v out or something like that and I got 2.4v out or something like that. Not a clue what this will do or how it will affect the driver.

So, I go about assembling this baby. Obviously replacing what i can with what I bought. The results?

This thing puts out almost 1A. Adjustable from like 100ma to 900ma+/-

I'm very happy too as the thing is muuuch easier to assemble.

Ken +1

 

[Ieon]

I really have no idea what a fusion driver is but it looks like a old driver kit dr.lava used to sell... just guessing.

But that is a nice simple driver ;D

 

[Kenom]

it was designed by Dr. Lava.  He then went and re-designed the board for the Kryton Groove.

The board layout for this one was put together by Bluefusion.

The most glaring error is how it's showing - on the one side input, and + on the exact same output. It should be reversed.

 

[rkcstr]

So are you using the 2.4V reference on there or did you get the correct ones?  I would guess that's why you're getting the ~doubled output current.

However, there may be some issues.

1.  the adj. pin of the IC may not be able to handle the extra voltage at 2.4V vs. the normal 1.25V
2.  I believe the IC is only rated for 800mA also.
3.  the 1R00 resistor, passing 900mA, is now also passing about 0.9W while it looks like a 1206 size and is probably only rated for 0.25W... that may lead to eventual, unpredictable failure of the resistor.

Also, have you tested the output over time?  I have a couple fusiondrives I put together and I've noticed that at the peak current (think it was about 460mA), the driver tends to output the current for about 15-30s, then the current starts dropping as the output voltage starts oscillating and it completely shuts off, comes back on again and continues to cycle every few seconds.  I'm guessing because the IC is overheating and shutting down due to thermal overload.

Anyway, I'd be interested to hear more about the results, but I just wanted to be sure you were aware of the potential issues.

 

[Kenom]

So are you using the 2.4V reference on there or did you get the correct ones?  I would guess that's why you're getting the ~doubled output current.

However, there may be some issues.

1.  the adj. pin of the IC may not be able to handle the extra voltage at 2.4V vs. the normal 1.25V
2.  I believe the IC is only rated for 800mA also.
3.  the 1R00 resistor, passing 900mA, is now also passing about 0.9W while it looks like a 1206 size and is probably only rated for 0.25W... that may lead to eventual, unpredictable failure of the resistor.

Also, have you tested the output over time?  I have a couple fusiondrives I put together and I've noticed that at the peak current (think it was about 460mA), the driver tends to output the current for about 15-30s, then the output starts dropping as the output starts oscillating and it completely shuts off, comes back on again and continues to cycle every few seconds.  I'm guessing because the IC is overheating and shutting down due to thermal overload.

Anyway, I'd be interested to hear more about the results, but I just wanted to be sure you were aware of the potential issues.

I was waiting for you to chime in. I've not a clue about anything you said other than the thermal issues. I DO know that the doggone driver has an issue with heat and will shut down from that. Also the 1 ohm resistor is a .5W (I got as big as I could) Output on the lm385 is 2.5v *(just checked LM385M3X-2.5CT-ND digikey) While the original was a 1.235v output (296-9562-5-ND digikey)

I have tested this driver on a Luxeon 1 Watt led for a few minutes and while it got hot, did not shut down from thermal protection. I'd be willing to send you one to play with if'n ya want.

 

[rkcstr]

I was waiting for you to chime in.

hehe  ;D

yeah, the heat seems to be an issue.  It's strange because using the same exact IC in the standard config with a resistor load for the current setting (like my driver) it doesn't seem to be as influenced by temp., while using the voltage reference config (like the fusiondrive), it does.  

Both in thermal overload shutdown and in the output current seem influenced.  I have noticed that if you change the output load, say from a ~3V load to a ~5V load, the current doesn't stay the same, but the current will also drift with temperature.  This seems to be slightly corrected by using a better voltage reference that has better thermal stability (I've used a Zetex one with better results) and also the actual manufacturer of the 1117 IC seems to make a difference as the TLV1117 by TI seems to work better than others I've tried from ON Semi, ST, etc, specifically the TLV1117Ixx version which has a lower operating temp (not that we need <0C operation, but wider range probably means better temp stability).  I think the fusiondrive and the groove drivers you have use the TI IC in the SOT-223 package.

I've experimented on my own version of this type of driver and managed to get it more stable, but still haven't completely solved any of the problems I saw.  It seems component characteristics are very critical, as with the volt. ref. and IC, plus some stabilizing capacitance on the input and some other places seem to help.

As for the temp stability, it also depends on the input/output voltage difference.  So if you increased the input voltage to the driver on your LED, it may just be enough to overload.  For example, I was powering a voltage of ~3V from the driver on ~6.4V input (yes, more than needed), which is when I was getting the shutdown.  Maybe had I run it off 4V (or +1V over the load), it would have been OK, but I was trying to compare operation to my current style driver.

Also, I have some 1W SMT 1R00 resistors, if you want some.  They're 2512 size, so bigger, but should handle the current, I believe.  

 

[rkcstr]

Another strange effect I've seen is that the minimum output current will be very low (I could get it down to <10mA) when cold, but if you run it at full current for a few second, so that it gets a little hot, then turn it back down, the minimum current will now be ~60-100mA.  But if then touch my fingers, absorbing some heat, it will drop again.

Also, similarly, the last prototype I made had this strange characteristic where if it was set all the way down to start, it would only put out the quiescent (minimum) current of the IC until I turned the pot up slightly, at which point it would jump up to a regular current output.  If you then turned it back down, it would then stay around 60-70mA.

 

[Kenom]

Hmmm.  I will defenitly take the 1W 1 ohm resistors.  I don't know how many places those badboys come in handy but I never seem to have enough. And to be perfectly honest with you. unless there is a really large pad around the hole, I'm really getting to hate through the hole resistor.

 

[rkcstr]

Well, I just bought a ton of em and I don't use them up very quickly (they're for my test load), so you're welcome to get as many as you want.  

here's the link to them on Mouser:
http://www.mouser.com/Search/Produc...Gvirtualkey61300000virtualkey71-CRCW2512-1-E3

When I put on on the board, it covered up the two pads for the resistor, but you could probably scrape off the solder mask on the traces and solder directly to it.  If you want, I can just mail you a few to try out and you can decide if you want more or not.

 

[Kenom]

sounds good to me.  I'm still learning how to get the size that you want.

The first time I ordered smt resistors they were 0402 and I still don't know what to do with them. Damn suckers are TEEEENIE.

 

[rkcstr]

heh, yeah 0402 would be really tiny... smallest I've used were 0603 and those things were barely visible. I had to use a loupe just to read the markings on some of them!

Anyway, I'll PM you for details.

 

[Kenom]

OK this is kind of a stupid question, but could I put a plain ol' diode inline here (obviously severing the trace) to put in a reverse polarity protection?

 

[DayOfShadows]

Ya but it would cause a voltage drop.
WOOT: POST 473

 

[Kenom]

Yeah I know about the voltage drop. However I figure considering the input voltage on this is going to be around 7.5v or more, it's not going to be an issue.

 

[rkcstr]

Yeah, that would work... just use a schottky diode rated for 1A and it should only cause ~0.5V drop vs the 0.7 to 1V for a standard rectifier.

Also, make sure whatever you're driving isn't connected to battery ground via the laser diode negative or it will defeat the protection.

 

[Kenom]

Yeah, that would work... just use a schottky diode rated for 1A and it should only cause ~0.5V drop vs the 0.7 to 1V for a standard rectifier.

Also, make sure whatever you're driving isn't connected to battery ground via the laser diode negative or it will defeat the protection.

DOH! Forgot about the neg. thing. Hmm I'll try to find a place for the diode in the positive path instead.