They have a very simple "driver" which consists of a resistor merely soldered onto the housing, it is powered off 3v.
So i connected about 8 of them in parallel to a 3v supply, initially they worked fine but all of a sudden they all dimmed down and faded away. What caused them to burn out even though i was powering them off a smooth 3v? They worked fine individually.
I tested all of them individually for 5-6 minutes and they worked just fine. Its just when i connected them in series. Its very odd as all of them dimmed at the same time and died.
adilmalik:
So i connected about 8 of them in parallel to a 3v supply,...
adilmalik:
Its just when i connected them in series. Its very odd as all of them dimmed at the same time and died.
First you posted that you connected "about 8" (about means 7, 8, maybe 9) "in parallel".
Then you had them "in series".
Oh my. Very odd, indeed.
I feel that I need to ask you to confirm the difference (in a drawing.)
They passed the individual 5-6 minute test.
How about the two in parallel 5-6 minute test?
The problem with a pointer that you then power with a normal supply is that the pointers rely on the internal resistance of the batteries to handle part of their current limiting.
I'm sorry, but I have a few of these guys here.
They're prepped "modules".
Maybe mine is/are different.
I use them with batteries (2X AAA).
I disconnected one and put it on the milliammeter, 25mA, same with the batteries or the power supply and it's all across the device.
Just relating based on my experience.
Maybe malik's device is different.
I dug up three others that I had still. In parallel, 78mA. As a bonus, everybody gets a close-up of my grotty keyboard.
Im sure they all have resistors pre soldered onto them. I think Mikes suggestion seems the most probable to me. I do remember the manufacturer posting a photo of running them with batteries while im using a PSU.
And yes i have the same ones, getting the same 25ma mark as you.
Ive ordered new, any precautions? i dont want to burn another lot...
Like Mike said all of them are not made the same" tricky" . Seeing the op said they have resistor on them tell us what it is.
From Mike link
Buy one that accepts an unregulated input voltage. Otherwise, you can still have problems even if you run the device from a regulated power supply. All laser pointers and most (but not all) modules will be of this type. However, if you get a deal that is too good to be true, corners may have been cut. A proper drive circuit will be more than a resistor and a couple of capacitors!
To confirm that the driver is regulating, start with an input near the bottom of the claimed voltage range and increase it slowly. The brightness of your laser diode should be rock solid. If it continues to increase even within the supposedly acceptable range of input voltage, something is wrong with either the laser diode (it is incompatible with the driver or damaged) or driver (it actually requires a regulated input or is incorrectly set up for the laser diode you are using). Stop right here and rectify the situation before you blow (yet another) laser diode!
There are two versions of these available, a 3V one which uses a "330" - 33 ohm resistor, and a 5V version which uses a "910" or 91 ohm resistor. Hooking up the latter, I measure 2.17 volts across the diode itself, stable over five minutes allowing the device to heat up to something like 33 degrees according to my thermometer module from eBay, though it is difficult to prove adequate contact.
So for the (nominal) 3V model, it would be drawing 25 mA, dissipating 54 mW and if indeed generating 5 mW of laser light, operating at 9% efficiency.
Similarly for the 5V model, drawing 31 mA which given the internal resistance of the Arduino driver reducing the actual supply voltage, is more-or-less within specification for a single Arduino pin.
Now those Runaway Pancake illustrates with epoxy encapsulation, I believe do contain an actual current controller according to the description by "Laserlands" who make a point of supplying certification for each unit they sell (in which case they can be driven with anything from 3 to 5V). Clearly, small variations in 5V supply with a "burden" across the resistor of 2.83 Volts will be less than a third as significant as the 0.83V across the 33 ohm resistor in the 3.3V version. Logically, you can just add about 58 ohms to each 3V module and run it from 5V.
If the supply is stable, then the use of a resistor for current control is actually perfectly adequate (but rather more so for the 5V version). Batteries, even Alkaline, are however anything but a stable supply so the performance of these 3V modules from batteries will be limited.
My module is still going over half an hour as I write this, and I have left it running before for days at a time. The original description that "all of them dimmed at the same time and died" cannot possibly be explained as component aging and failure; I have to say that there must be something wrong with the "smooth 3v" supply. I think adilmalik needs to explain exactly what this supply is?
thanks guys fingers crossed