M-140 diode death?

Hi, first time here.

I wrote to Jordan today and he suggested I post here.

I seemed to have killed another M-140 diode. It died during a long engraving (about 1 hour). This is the 3rd time this has happened.

The first time I thought that it might be caused by my driver possibly not controlling the current correctly. The second time is a mystery but, now third time causes MUCH anxiety.

I have checked and verified that my controller cannot deliver more than 1.5 amps to the diode. It is being used to engrave on wood and I have a lot more work to do. I am using a pulsed G-code that turns the laser on/off between 0 and full power in 255 steps. Does the diode need time to rest after a ON period?

Now my only thoughts are HEAT. I have a 2” X 2” X 2-1/2” aluminum block with a muffin fan blowing on it. The hole is about .5mm larger than the housing so it is NOT a tight fit and the diode is being held in place with a screw. During a run, I feel the block and it is a little warm to the touch but not hot. I am thinking that it still is not enough contact to cool the diode and it is burning out do to heat. I have ordered another heat sink with a tighter fit and I will use thermal compound since there is a much tighter fit.

My S0J6 diode with X-drive keeps on working but I cannot control the intensity like I need. The controller I am using is made from a Arduino and a Maxium LED controller that seems to be rock solid (now that I have a good program). The current is set using a .13 ohm "sense" resistor on the Max board and cannot deliver more that 1.5 amp output. The arduino turns the step and direction pulses into a PWM signal that the LED controller needs. This should not cause the M-140 to have any problems with current. It has a 56 uHy ripple filter on the output and delivers a clean output to the laser diode.

Another question about the G-2 lens. I have several and now they are mixed up with other lens, how do I tell them apart? Several have only one lens nearer the diode and some have more than one lens. I cannot tell the difference with pictures on the web.

I am a "OLD" electronic tech and have more than 30 years in the aerospace industry with NASA and know what I am doing (most of the time) but these laser diodes don’t always do what I think they should.

If you have any thoughts I would greatly appreciate them.

Thanks,

Joseph Lawrence

Heating is definitely a potential issue,
but in an engraver, the laser is also being
turned on and off A LOT. The driver simply
cannot have overshoot beyond the ratings of
the diode. Since this is an LED driver,
it's a little iffy. LEDs can handle some
overshoot. So the short answer is a good
driver and a finned heatsink.

Can you post a photo / schematic / link to your driver? That's a key piece of missing info.

One of the reasons I referred you here as I am not familiar with the driver you are using and you seem pretty confident with it but it has been there for three diode deaths so was hoping you would get some other opinions than mine and since being a driver designed for LED's I am very skeptical of it. For drivers with modulation I see these come most recommended.

Flexmod P3. Great driver but usually on backorder.
FlexMod P3 Laser Driver

Lasertack drivers. Another great set of drivers
https://www.lasertack.com/en/laser-diode-drivers

Lasershowparts drivers very good driver but only available in dual channel.
Lasershow Parts - 2 channel analogue diode driver

Also check out this thread with some other options.
Are FlexMod P3's still available or is there an equivalent that is ready to ship?

...still waiting on the details of your driver

I couldn't find anything called a "Maxium LED Controller".

Perhaps what you mean is that you built your own driver around something like a MAX16819 or MAX16820 ?

If so, show us your schematic. I'll tell you, when it comes to switching drivers, "looks like it's working" is just the first step along the path to a truly rock solid driver. Appearances are deceptive with boosts and bucks, and the path is littered with dead diodes.

It's fairly simple (well, it's not insanely difficult) to make a switching driver the runs a diode. Making one that truly runs with stability, is a whole different story.

Joelaw said:

Hi, first time here.

I wrote to Jordan today and he suggested I post here.

I seemed to have killed another M-140 diode. It died during a long engraving (about 1 hour). This is the 3rd time this has happened.

The first time I thought that it might be caused by my driver possibly not controlling the current correctly. The second time is a mystery but, now third time causes MUCH anxiety.

I have checked and verified that my controller cannot deliver more than 1.5 amps to the diode. It is being used to engrave on wood and I have a lot more work to do. I am using a pulsed G-code that turns the laser on/off between 0 and full power in 255 steps. Does the diode need time to rest after a ON period?

Now my only thoughts are HEAT. I have a 2” X 2” X 2-1/2” aluminum block with a muffin fan blowing on it. The hole is about .5mm larger than the housing so it is NOT a tight fit and the diode is being held in place with a screw. During a run, I feel the block and it is a little warm to the touch but not hot. I am thinking that it still is not enough contact to cool the diode and it is burning out do to heat. I have ordered another heat sink with a tighter fit and I will use thermal compound since there is a much tighter fit.

My S0J6 diode with X-drive keeps on working but I cannot control the intensity like I need. The controller I am using is made from a Arduino and a Maxium LED controller that seems to be rock solid (now that I have a good program). The current is set using a .13 ohm "sense" resistor on the Max board and cannot deliver more that 1.5 amp output. The arduino turns the step and direction pulses into a PWM signal that the LED controller needs. This should not cause the M-140 to have any problems with current. It has a 56 uHy ripple filter on the output and delivers a clean output to the laser diode.

Another question about the G-2 lens. I have several and now they are mixed up with other lens, how do I tell them apart? Several have only one lens nearer the diode and some have more than one lens. I cannot tell the difference with pictures on the web.

I am a "OLD" electronic tech and have more than 30 years in the aerospace industry with NASA and know what I am doing (most of the time) but these laser diodes don’t always do what I think they should.

If you have any thoughts I would greatly appreciate them.

Thanks,

Joseph Lawrence

Click to expand...

Hi Joe,
Looks like we share something in common. I killed an M140 last night myself! It's a mystery to me as well as to exactly what happened. I was running it at half power actually testing a new LPM I just received and suddenly the diode went out. After quickly trying to figure out what was going on I realized that the negative lead had shorted over to the case lead. Now in theory I can't see where this would have damaged the diode, but as soon as I unshorted it the diode came back to life... For about 2 seconds where it's output quickly began to fade and about 30 seconds later I had a pretty blue LED. After ordering a replacement I too spoke with DTR and I'm not sure either of us really understands what happened. The best we could come up with is that I was running my DMM in series on the cathode side of the diode for current monitoring and DTR feels it best to monitor the input side of my 317 instead.

Anyway... The one thing that does stick out to me in your case is what you mentioned about the heat sink. I'm a "computer guy" myself, and what I've been using for heat sinks is some old Xeon heat sinks we removed from some decommissioned servers. These are about 3 1/2" x 3 1/2" x 2" and have a marvelous solid copper core that runs top to bottom (about 2" thick) and is a little over 1" in diameter right in the center of the heatsink. I drill these out 15/32" and then follow with a slight reaming and the typical 12mm module is a press fit. I use a paper towel to smear a VERY light coat of artic silver on the module then press fit it in. No securing screws needed. The thing is, thermal paste isn't really a very good transfer medium for heat. It's really made just to "fill in" the microscopic valley's in metal finish to get slightly better contact. The reason I mention this is, I've seen MANY MANY cases in my time where someone has destroyed a CPU because they put too much heat sink compound on. If you get a little too much then it actually forms a "layer" between the metal surfaces instead of just filling in the gaps. That layer of compound is MUCH worse as conducting heat than if you had just left plain metal to metal contact.

Anyway, just securing it with screws in a larger hole isn't good either. The hole is round, the diode module is round, so when secured in this way think about how LITTLE actual contact with the heat sink you have. If I had to take a guess, assuming the driver isn't overshooting when it switches on, it was probably heat that killed it.

Sorry about your diode... I feel your pain.

Rhd,

Yes, I am using the Maxium "MAX16820" chip. I purchased an evaluation board that I then used with a Arduino design step and dir to PWM to run the Max16820 board.

Maybe I am missing something but the MAX16820 should be able to drive a Laser diode. Possibly overshoot since I am pulsing the Laser pretty fast. I haven't tried to scope the output signal to measure exactly what it is doing.

I still think that it died because of heat. I have a thermocouple and will mount it on the next heat sink to verify the temp. I think that the max temp for the M-140 is around 50 C and that is pretty low. The block mount that I was using did get warm to the touch on the outside but inside it could get much hotter and probably over the 50C limits.

My wife said just keep installing new Laser diodes when it goes out. She is thinking about Christmas light LED's and their cost.http://laserpointerforums.com/images/smilies/smile.gif

More work to be done.

Thanks, for the replies and help.

Joelaw

Joelaw said:

Yes, I am using the Maxium "MAX16820" chip. I purchased an evaluation board that I then used with a Arduino design step and dir to PWM to run the Max16820 board.

Maybe I am missing something but the MAX16820 should be able to drive a Laser diode. Possibly overshoot since I am pulsing the Laser pretty fast. I haven't tried to scope the output signal to measure exactly what it is doing.

Click to expand...

Why? Just because the input / output specs hit the same voltages? There are a whole lot of LED drivers with specs that should be able to drive a laser diode on paper. The IC might be fine for ultimate use in a laser driver, but there's no reason to assume the evaluation board is. If you're going to go off-book and use an unheard-of driver, you should ideally be doing it for some purpose. This evaluation board certainly can't be cheaper than a proper laser driver.... so why not use a proper laser driver?

More to the point though, I see some pretty obvious death-causing problems with this evaluation board. Unless I'm missing something, there's no output cap. Like, none. I see a 1uF input cap, and I see a 1uF cap on the IC's VCC, but absolutely nothing on the output to the LED (errrr.... laser diode). That's pretty scary for laser diode driving, and probably exactly why you keep frying them. On the bright side, at least it uses a 56uH inductor and is pretty high frequency, but I don't see how that gets you off the hook for needing an output capacitor. You could run the equations to figure out what kind of ripple you're seeing, but my bet is a LOT, especially if your driver's input voltage is higher than 6 or 7 Volts.

At 1.5A of target current, with no output cap, you could very easily be peaking over the death cliff of an M140. In fact, I'm surprised you're not killing more diodes right off the bat.

Joelaw said:

I still think that it died because of heat. I have a thermocouple and will mount it on the next heat sink to verify the temp. I think that the max temp for the M-140 is around 50 C and that is pretty low. The block mount that I was using did get warm to the touch on the outside but inside it could get much hotter and probably over the 50C limits.

Click to expand...

Heat certainly is something to keep an eye on but I thought you said the heatsink was only mildly warm?

Hold up, I also noticed that your inductor, the CR75NP-560KC, has a saturation current of around 1A.

For 1.5A of output, that's going to be another clear deal killer.

DTR said:

Heat certainly is something to keep an eye on but I thought you said the heatsink was only mildly warm?

Click to expand...

That really doesn't mean much... It could be transferring heat wonderfully and only getting mildly warm because of being very effective at dispersing that heat into the atmosphere. OR it could be only mildly warm because it has a terrible connection with the module and only a small amount of heat is being transferred from the diode to the heat sink. In that case it's still only going to get mildly warm, because all the remaining heat is being held in the module.

rusirius said:

That really doesn't mean much... It could be transferring heat wonderfully and only getting mildly warm because of being very effective at dispersing that heat into the atmosphere. OR it could be only mildly warm because it has a terrible connection with the module and only a small amount of heat is being transferred from the diode to the heat sink. In that case it's still only going to get mildly warm, because all the remaining heat is being held in the module.

Click to expand...

Possible that heat is a problem too, but there's really no mystery here, the big huge obvious problem in my mind is this driver.

No output cap, an inductor that is running at least 50% above saturation current when it should be about 40% below saturation... big obvious "do not pass go" style problems with this buck. Add to that the fact that you're PWMing it, and it's a recipe for disaster. Not just a recipe, it's a pre-made microwave dinner of disaster

Rhd,

I am using the evaluation board but changed the Schottky diode and the choke to 3amp models. You are right about the cap on the output though. I should have something there.

I first started this project after seeing a post about laser engraving photos on this site. They were using an encoder and opamp to drive the laser. I basically followed what they were doing and using the max16820 to control the laser.

The parts count and price are pretty low ($10-$15) plus the PCB. It sounded better to me than using mechanical step motor driven encoders.

When this system is NOT blowing diodes, it works wonderfully. Does exactly what I wanted it to do and would be very easy to replicate. Of course the problems are always in the details.

As stated, I am not familiar with laser diodes and their quirks. Really don't find much on the web as to specs and design info to make better drivers.

I looked up the drivers suggested before and none tell me anything about what they can or cannot do. Does anybody know about any other drivers that can take step and direction commands and control a laser diode with all of the protections needed to keep it alive?

Also about the heat sink. I think that the outside of the block is not getting very warm because the contact area between the diode housing and the block are not good. This makes the diode very hot and the block not so much.

I am in the process of fixing that in the future. I am sure that the diode must have been well over the 50C max.


Thanks,

Joelaw

Joelaw said:

Also about the heat sink. I think that the outside of the block is not getting very warm because the contact area between the diode housing and the block are not good. This makes the diode very hot and the block not so much.

I am in the process of fixing that in the future. I am sure that the diode must have been well over the 50C max.


Thanks,

Joelaw

Click to expand...

Yea I was assuming good contact with the sink. The hole should be a perfect 12.00mm with a set screw as the module is just slightly undersized @ 11.96mm. You can also make an interference type and press the module in by just slightly under sizing the sink hole but it is easier for swapping out if needed when you don't use the interference press style sink.:beer:

If you have an oscilloscope, then by all
means make sure the current does not spike
above 2A, even for a nanosecond.

rusirius said:

Hi Joe,
Looks like we share something in common. I killed an M140 last night myself! It's a mystery to me as well as to exactly what happened. I was running it at half power actually testing a new LPM I just received and suddenly the diode went out. After quickly trying to figure out what was going on I realized that the negative lead had shorted over to the case lead. Now in theory I can't see where this would have damaged the diode, but as soon as I unshorted it the diode came back to life... For about 2 seconds where it's output quickly began to fade and about 30 seconds later I had a pretty blue LED. After ordering a replacement I too spoke with DTR and I'm not sure either of us really understands what happened. The best we could come up with is that I was running my DMM in series on the cathode side of the diode for current monitoring and DTR feels it best to monitor the input side of my 317 instead.

Click to expand...

There are a few things that could have
happened. One possibiity is that the
inductive energy stored in the multimeter
leads and elsewhere when it was shorted
suddenly became free and caused a power
excursion transient. Another thing is
drivers are not designed to deal with a
shorted output. The output voltage
suddenly goes from near 0 to the 5V
neighborhood when the short is cleared and
the feedback loop is unable to compensate
quickly enough. ESD is another
possibility. If it happens again, shut off
the power before clearing the short and
test the driver using a dummy load to make
sure it is still functioning properly.

Why would a laser driver need to take take "step and direction commands" ? Isn't that just needed for your stepper motor drivers?