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A Question on the m140 Laser Diode

MentallyCoded

Sep 7, 2017
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I have recently completed a build for a 2W laser using the M140 Diode. I am currently running the diode off of a homemade driver set at 1.8A with a voltage of 6.11V. My question is, will this high of a voltage effect the life of the diode or does it not matter? Would it be better to run off of, say, 5V at 1.8A?
 

Harald Kapp

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The diode needs to be driven by a regulated current. The voltage drop will adjust according to the V-I characteristic of the diode. It will not be possible to use 5 V at 1.8 A at the same time.

This datasheet specifies that the diode should be run off 1.7 A max and only for a short time. For longer lifetime a current of 1.2 A is recommended. Also additional cooling is recommended.
The optimal power level is 1 W to ensure long lifetime.
ALways use a constant current laser driver, never a constant voltage source!
 

MentallyCoded

Sep 7, 2017
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The diode needs to be driven by a regulated current. The voltage drop will adjust according to the V-I characteristic of the diode. It will not be possible to use 5 V at 1.8 A at the same time.

This datasheet specifies that the diode should be run off 1.7 A max and only for a short time. For longer lifetime a current of 1.2 A is recommended. Also additional cooling is recommended.
The optimal power level is 1 W to ensure long lifetime.
ALways use a constant current laser driver, never a constant voltage source!

I guess I didnt specify that very well. To put it in better terms, I am using a homemade current driver set at a constant 1.8A with a maximum output voltage of 6.11V from a 12V source to create that 1.8A current if that clears it up any (I am not running the laser directly from the power source, instead, I am stepping down the voltage and creating a constant current). As for the cooling, I already have a heatsink installed and am working on installing a fan for extra cooling. I usually only run the laser for no more than 1 minute at a time.
 

Paquito

Jan 23, 2018
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I guess I didnt specify that very well. To put it in better terms, I am using a homemade current driver set at a constant 1.8A with a maximum output voltage of 6.11V from a 12V source to create that 1.8A current if that clears it up any (I am not running the laser directly from the power source, instead, I am stepping down the voltage and creating a constant current). As for the cooling, I already have a heatsink installed and am working on installing a fan for extra cooling. I usually only run the laser for no more than 1 minute at a time.
 

Paquito

Jan 23, 2018
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Hello, could you please tell me how did you made your homemade current driver for laser Diode ? Like the composents you use or the electronic assembly. Because i’m building a laser for a school project. Thanks, you will help me a lot.
 

MentallyCoded

Sep 7, 2017
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Hello, could you please tell me how did you made your homemade current driver for laser Diode ? Like the composents you use or the electronic assembly. Because i’m building a laser for a school project. Thanks, you will help me a lot.
So there are two easy choices that are simply a component you would buy such as a buck converter or an lm317 (small and compact voltage regulator component)to which I had modeled my driver after. using either of these components will allow you to hook your power source (say 12v) to the voltage regulator and receive a fixed output voltage on the other side of the regulator. At this point you would simply use V=IR to calculate the proper amount of resistance to set on this side of the circuit for the current you want the laser to run on. The resistance of the diode itself will not matter since any resistance seen by the diode will only decrease the current flow (it is minimal anyway and decreases as the diode heats up). Having a voltage regulator allows for you to keep a steady voltage and current output while the source can have varying voltage levels. This allows for a steady current to the diode and less stress on the diode itself. It is also worth noting that I had some issues getting the laser to laze until I upped the voltage on the secondary side of the voltage regulator even though i made changes to resistance to allow the current to remain the same in both cases. I Hope that helped.
 

Paquito

Jan 23, 2018
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So there are two easy choices that are simply a component you would buy such as a buck converter or an lm317 (small and compact voltage regulator component)to which I had modeled my driver after. using either of these components will allow you to hook your power source (say 12v) to the voltage regulator and receive a fixed output voltage on the other side of the regulator. At this point you would simply use V=IR to calculate the proper amount of resistance to set on this side of the circuit for the current you want the laser to run on. The resistance of the diode itself will not matter since any resistance seen by the diode will only decrease the current flow (it is minimal anyway and decreases as the diode heats up). Having a voltage regulator allows for you to keep a steady voltage and current output while the source can have varying voltage levels. This allows for a steady current to the diode and less stress on the diode itself. It is also worth noting that I had some issues getting the laser to laze until I upped the voltage on the secondary side of the voltage regulator even though i made changes to resistance to allow the current to remain the same in both cases. I Hope that helped.
Thanks a lot,
But does a current regulator system exists ? To be sure to not burn the diode, I thought for a capacitor to avoid high current peaks but which one ?
 

BobK

Jan 5, 2010
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An LM317 can be easily configured as a current regulator. Check out the datasheet for the circuit.

Bob
 
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