Hot Hot Hot!!

[wicked1]

Everyone's always saying "these blu-ray diodes don't get that hot..  Even in just the heatsink they came in"  So, I had one hooked up for testing..  150ma..  It is HOT!  I got my finger wet and touched it and it sizzled.  That's after being on for about 10 seconds.  

is this right??  They all seem to be like this, too. My only other guess is that my meter is wrong, and I'm way over powering it. But I tested w/ two meters! (I have had 2 inaccurate meters in the past.. so thats not impossible)

 

[lasersbee]

Where is your meter hooked up in the circuit ??
What type of driver are you using ??
what is the supply voltage to the driver??

 

[daguin]

Everyone's always saying "these blu-ray diodes don't get that hot..  Even in just the heatsink they came in"  So, I had one hooked up for testing..  150ma..  It is HOT!  I got my finger wet and touched it and it sizzled.  That's after being on for about 10 seconds.  

is this right??  They all seem to be like this, too.  My only other guess is that my meter is wrong, and I'm way over powering it.  But I tested w/ two meters!  (I have had 2 inaccurate meters in the past.. so thats not impossible)

At 150mA and higher these diodes do indeed get very hot. They will burn themselves out. That's why my high powered builds all have good heat sinks and limited duty cycles. If you keep them below about 130mA (below 110mA is even better) then they stay pretty cool.

Peace,
dave

 

[Kage]

It is really pretty easy to predict how hot the heat sink will get using simple math.

For example, if you are driving an 803t at 150mA, it is probably dropping about 6V across it, and .15A x 6V = .9W of power to dissipate.

If our heat sink has a thermal resistance to Air of 20 deg C/Watt, then 20 x .9W = 18 deg C temperature rise. So if we run this in a 20 deg C environment, 20 + 18 = 38C. And the temperature of the heat sink should equalize at around 38 degrees Centigrade or 100 F.

Of course we have no way of knowing the actual junction temperature of the diode unless someone can come up with a real spec sheet with a junction to case thermal resistance, and a derating curve would be nice too.

 

[wicked1]

Thanks a lot guys!! Its final home will be my MXDL w/ plenty of heatsinking. (tho I've already killed 2 diodes in this setup.. 190 died.. 17~ died.. so now trying 150.)

 

[Ace82]

Do they show any signs of failure before they actually burn out, or do they just die? Because you could damage them during extraction, or installation/soldering. And how long were you running it before you it died, whats your duty cycle? Because I have one running strong (knock on wood) at ~180ma. And yes it gets warm after 10 sec, but that's why I never have it on longer then 20-30 sec then at least 10 sec cool down.

 

[wicked1]

they showed no sign of failure.  It was during times of a lot of on/off action...  on 10 seconds, off 5.   on 10 seconds, off 15, on 2 seconds, off 1 second, etc,, (Basically when I'm showing other people the laser..  and combined 'on' times never amounts to much before it dies)  I used them w/ longer duty cycle, longer off time..  on 2 minutes, off an hour for months, and they are fine.  
I think they're just super shy.  They do fine w/ just me, but when a group of people are around..  dead.

I got a new power supply for this rebuild.. I started to suspect it. I'll see how it fairs this weekend.