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laser driver getting hot.

dark racer

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Feb 8, 2013
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hey. good afternoon.

i bought this laser module https://nl.aliexpress.com/item/1-6-W-445nm-Blauw-Violet-Licht-Laser-Module-Graveur-Accessoire-voor-CNC-Laser-Carving-Graveermachine/32976516190.html?spm=a2g0s.9042311.0.0.75de4c4dyHjdyg

wich arrived yesterday.
i wired it up like this

so the 12v input has it's own sepperate 12v rail from an atx psu (it's the psu i turn my 3d printer on with) (also measured with a multimeter btw. 11.9v)
i put a 12v to 5v regulator between the fan output (2 wires powered by a mosfet with a floating ground. basicly the + always outputs 12v and the ground opens and closes to created a pwm signal)
so there is an lm8705cv turning that 0-12v signal into a 0-5v signal. (confirmed with multimeter)

when i turn the power on. the laser just turns on. and it stays on uncontrollable. untill the driver starts heating up.
when the driver is warm. and there is 0v on the control plug the laser will dim to like 1% or something. not off. (only if the control is plugged in though. if i leave it unplugged the laser stays on)
if i turn the fan speed to 99% (this gives it a pulse width modulated signal with a duty cycle of 99%) the laser is on full power.
however if i set it to 100% wich is a full duty cycle. constant 5v, the laser just dims to 1% again.

on the driver there are 2 components heating up.
there is a 1ohm resistor heating up. this must be part of the current limiting circuit.
and there is a single direction diode. near the 12v input that also heats up.
these are hot enoegh to burn skin. i added heatsinks but that just slows down the heating. eventually it's still too hot to touch.

the laser module itself (feeling the heat of the heatsink) also gets warm. not hot but warm. though i would not be supprised if it would get hotter and hotter on longer engravings.. should i just 3d print an enclosure for the driver and laser and just run a high powered fan to keep things cool? or is this thing broken and should i ask for a refund?

(currently making a video and uploading it to youtube so you can see this)

laser turning off at 100% signal. (don't worry i know about the light. my eyes are not the camera. i am not looking at the dangerous light)



laser is controllable in brightness. and a look at the driver without the added heatsinks. and me burning my finger on the diode.
(again. i am not looking in the direction of this laser light.) keeping it even out of my peripheral vision. or blocking it with the other hand.


video showing the laser dimming after the driver heats up. (there is a 0v signal so the laser should be off from the start. but it only goes off after heating up)
i did not know this at that point yet. so i thought it was dimming because it heated up..


and the last video
here i did know it would only be controllable when warm
 
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lasersbee

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You need to check the Current that the Laser Diode is
drawing... There is a blue multiturn trimpot on the LD
Driver PCB. It looks like an LD Current control and may
need to be reduced. Perhaps it was adjusted too high
from the factory or you may have moved it.

Did you test the Laser on the bench before hooking
it to your 3D printer electrical/electronics ???

Jerry
 
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dark racer

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bench? XD sorry i am not that fortunate. also my multimeter is broken. i cannot measure amps. (i can check the wattage on the watt meter. and calculate it though.) it's supposed to be 1700mA

the trimpot is still on there and the screw to adjust it is fixed with some red glue or composit or whatever that is.
so i am just assuming it's correct.
i'll do the watt and voltage calculation now


21 watts at 11.9 volts. (basicly 12)
so that's around 1745-1750 mA.
it's a little over but not much.

but then if i want to adjust it. is it clockwise or counterclockwise. because that depends on how they wired it up.
and then it still would only respond to commands if the driver is warm.


i am currently in fusion360 working on a mount so i can put a bigger fan on the laser. and have that same fan also blow air over the driver.
but you're saying. if i adjust the pot and get this thing to for example. 1500mA that both the laser module and the driver won't get anywhere near as hot as they do now and i won't need a bigger fan?

if i can avoid touching that i would preffer that. if something dies during engraving and they want me to send it back before a refund, i might not get a refund.
 
Last edited:

dark racer

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ok so an update.

if you unplug the ttl port the laser is just always on at full strenght.
so instead of using the onboard ttl. i tried an external mosfet.

and it works. i can control the laser's intensity. and even dim it to a point that i could focus without using the glasses. (less then 5mW i'm sure)

but best of all. the driver doesn't heat up. (much)
64618
 

lasersbee

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So the problem was too much current going to the
Laser Diode.
Glad you got it fixed.
BTW a kitchen table makes a great bench in a pinch.:)

Jerry
 

dark racer

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So the problem was too much current going to the
Laser Diode.
Glad you got it fixed.
BTW a kitchen table makes a great bench in a pinch.:)

Jerry
oh i thought you ment a power supply., a test bench.

i do have a work area for testing it on.
i'm not sure about the current. it should still be drawing 1700mA
i just stopped using the ttl.
and to protect my motherboard i used a mosfet.

i think the ttl just doesn't work propperly. bad design.
instead of shutting off power it just converts all energy into heat. and did it slowly at that
 

paul1598419

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I would have to agree that is a bad design. Some of these Chinese driver boards are functional. Unfortunately, there are too many that are not with no way of knowing which is which ahead of time.
 

LaserRanger

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Hey Paul, is there any thread where laser drivers are discussed? Not necessarily from a specific vendor but like reviews or test results of every driver available in a single thread so they can be compared and such... Ive searched in its section of the forum but I haven't found much info on most drivers available on ebay that I currently own. It would be rather expensive to replace all my laser drivers that I purchased at $7-10 with laser drivers that go for $25-40 each
 

paul1598419

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Hey Paul, is there any thread where laser drivers are discussed? Not necessarily from a specific vendor but like reviews or test results of every driver available in a single thread so they can be compared and such... Ive searched in its section of the forum but I haven't found much info on most drivers available on ebay that I currently own. It would be rather expensive to replace all my laser drivers that I purchased at $7-10 with laser drivers that go for $25-40 each
No, I have never seen one either. About the best you will find is DTR's website on the drivers he is currently selling. Lazeerer did have some threads on his drivers too. Those are still pertinent if you have some of those drivers.
 

LaserRanger

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@paul1598419 Well I'm gonna have to slowly buy good drivers to replace the ones I have at the moment Tha KS buddy. I like the small boost driver on his website. The microflex was it? I believe you recommended it to me at one point I believe
 




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