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Hi Guys and gals,

I have a project that requires driving Mitsubishi ML520G51 laser diodes, the project needs each one to vary in power for a visual effect. each diode indipendantly..

I have searched around and see some circuits using LM317s and these are ok but over powered for such diodes, I have also seen some other circuits using International Rectifier parts but I cannot find any specific details about the parts. I am assuming a simple current limited driver can be constructed using a regulator and a few other descreate components.

I will signal these diodes with some analog outputs of a microcontroller and want to find a safe way to drive the diodes so the specifications are not exceeded.

Does anyone have such a circuit?

Andy

andyf97 wrote:Mitsubishi ML520G51 laser diodes, the project needs each one to vary in power for a visual effect. each diode indipendantly... Does anyone have such a circuit?

Do you have a datasheet from this one - Does the diode have a monitor diode?

rvogt1964 wrote:

andyf97 wrote:Mitsubishi ML520G51 laser diodes, the project needs each one to vary in power for a visual effect. each diode indipendantly... Does anyone have such a circuit?

Do you have a datasheet from this one - Does the diode have a monitor diode?

Yes but its 1.7 meg so I have captured the relevant data to an image.

I dont think the diode has any monitoring.

andyf97 wrote:Does anyone have such a circuit?

a circuit of a ld driver:

viewtopic.php?t=39887

rvogt1964 wrote:

andyf97 wrote:Does anyone have such a circuit?

a circuit of a ld driver:

viewtopic.php?t=39887

Hi rvogt1964,

Thank you for your help but..

I saw that page but the first is TTL ON/OFF and the other looks like a kind of analog based on an R/C ladder that will take up too many pins of the microchip. I need to find a sollution where one analog output from the PIC drives one diode. I have 5 analog pins for 5 diodes.

The ladder system is very nice if i was just driving one diode. To do this way i would need a lot of extra logic to toggle those ladder stages and likely an AtoD converter for each set of 8. I feel there must be a way to drive one direct with few components but I am lost to know which.

andyf97 wrote:...and the other looks like a kind of analog based on an R/C ladder that will take up too many pins of the microchip.

Hi,

at this moment, i just about to develope a circuit for an analog LD-driver
with a MCU from Microchip - It will use PWM to drive LD's analog.

Because my circuit use also a monitor diode, to check the power to drive
the LD with the given electrical characteristics. I believe it will also run
without it, alternate you have to use a resistor to make a constant power
supply for the LD.

i want to draw my circuit "on paper", to put it here for you. Please give me
a short time to do that later!

rvogt1964 wrote:i want to draw my circuit "on paper", to put it here for you. Please give me a short time to do that later!

Here you find my base circuit without LCD-Display, normally it shows all
values which are used currently for the LD (Current consumption, monitor
diode Voltage, Analog-signal out (percent)).

The firmware will be in Beta-status, but it run's (you see the picture of the
"little" red lightning LD). So i hope it will give you some Idears to your
project specifications.