DIY Homemade laser diode driver

jaap75 · Jan 15, 2008

Hello,

By using 2 10 ohm risistors parralel i'm getting 2.15v @ my diode.
Thats not enought, so what's the best option for the risistors( ohm ) to get a good voltage at my diode.

Please let me know,
Yoeri

troop231 · Jan 15, 2008

jaap75 said:
Hello,

By using 2 10 ohm risistors parralel i'm getting 2.15v @ my diode.
Thats not enought, so what's the best option for the risistors( ohm ) to get a good voltage at my diode.

Please let me know,
Yoeri

What you currently have is 5 ohms total, which will yield the best lifespan and burning of the diode. However, if this doesnt float youre boat and you are not to concerned about the diode life, then you can try 4 ohms total or maybe 3 ohms if you dare? lol

rog8811 · Jan 15, 2008

By using 2 10 ohm risistors parralel i'm getting 2.15v @ my diode.
Thats not enought, so what's the best option for the risistors( ohm ) to get a good voltage at my diode.

Do I assume you are using the driver that this thread is all about i.e the LM317?

If so don't start by changing resistance values, test out the circuit to see that it is working properly. This thread describes a constant current circuit where the voltage is whatever the LD requires at a given current. If the volts are too low it could be that your input voltage is too low for the LM to regulate.

Regards rog8811

jaap75 · Jan 18, 2008

Hi,

I tried replacing all of the component(accapt for the risistors, But still only 2.17volts @ my diode.
My battery's are both fully charged and giving of both 3.0 volts.

You see a vague red stip when I point it 5cm above the serface.

Should I tray changing the risitor value?

amkdeath · Jan 18, 2008

jaap75 said:
Hi,

I tried replacing all of the component(accapt for the risistors, But still only 2.17volts @ my diode.
My battery's are both fully charged and giving of both 3.0 volts.

You see a vague red stip when I point it 5cm above the serface.

Should I tray changing the risitor value?

we need pics

try inputing 9v in the circuit

pics of the focused dot on a wall 12ft away

Gazoo · Jan 18, 2008

jaap75 said:
Hi,

I tried replacing all of the component(accapt for the risistors, But still only 2.17volts @ my diode.
My battery's are both fully charged and giving of both 3.0 volts.

You see a vague red stip when I point it 5cm above the serface.

Should I tray changing the risitor value?

Measure the total voltage of the batteries with the circuit powered on and let is know what it is.

MTG18 · Jan 19, 2008

Hi,
I am sure this has been asked many times before but after scanning these forums for hours, I was unable to find a direct strait-forward answer. If their is one out their please just point me in the right direction.

I realize that this driver was designed to be safe and versatile and that it is great for this reason. But because of its size it may be difficult to fit into small sized applications. On the other end of the scale we have the direct connect option which is dangerous and risky for the life of the diode. My question is . . . is their a middle ground driving circuit that is reasonably safe but simpler and smaller. Perhaps something like a resistor and capacitor would suffice for a small, simple application. Where the resistor is limiting current the way it would in a basic LED circuit and the cap would protect against voltage irregularities.

Would a circuit like this be reasonably safe? What would be the downfalls?

Also, their are many Online Resistor Calculators that calculate resistance values for a resistor in a LED circuit with a given voltage and operating current. Can these be used for LD's the same way? Or are they too different?

Thanks to everyone for making this forum so informative and useful for any beginning laser enthusiast!

~ MTG

amkdeath · Jan 19, 2008

MTG18 said:
Hi,
I am sure this has been asked many times before but after scanning these forums for hours, I was unable to find a direct strait-forward answer. If their is one out their please just point me in the right direction.

I realize that this driver was designed to be safe and versatile and that it is great for this reason. But because of its size it may be difficult to fit into small sized applications. On the other end of the scale we have the direct connect option which is dangerous and risky for the life of the diode. My question is . . . is their a middle ground driving circuit that is reasonably safe but simpler and smaller. Perhaps something like a resistor and capacitor would suffice for a small, simple application. Where the resistor is limiting current the way it would in a basic LED circuit and the cap would protect against voltage irregularities.

Would a circuit like this be reasonably safe? What would be the downfalls?

Also, their are many Online Resistor Calculators that calculate resistance values for a resistor in a LED circuit with a given voltage and operating current. Can these be used for LD's the same way? Or are they too different?

Thanks to everyone for making this forum so informative and useful for any beginning laser enthusiast!

~ MTG

you can buy an AMC 7135 regulated circuit off of dealextreme.com and hook that up to your diode with a 33 ohm resistor in parallel with your laser diode.

that will fit in your flashlight

the LM317T can be made very small

just grind off the tab, and using no PCB connect the resistor (5homs) from adj to vout directly, and cutting the leads of the resistor very short so that when connected to the pins it doesnt get taller than the black part of the LM317T

attatch the input of the flashlight to the vin,

attach + on diode to vout

connect - on flashlight to the diode

solder a small capacitor and a rectifier diode in parallel with your laser diode

this will be small enought to fit anywhere, and if you do it right, mabe even in the aixiz housing

there are also other options, like the fusion drives, going for $4 ea + 1.50 shipping in the group buys section

those work with bluray and red diodes, and fit in your axiz housin, and are VERY TINY

overall there are many possibilities, just whatever you do, DO NOT do the resistor and cap setup, as a driver would protect your diode more

regards,

amk

Gazoo · Jan 19, 2008

One note about the 7135 is the diode needs to be isolated from the case. The ground side from the 7135 to the diode comes off the regulator, not the battery like a 317. Other than that, it is a very good regulator.

MTG18 · Jan 19, 2008

Thanks for your help and suggestion! I am still curious what the downfalls of the resistor/cap circuit are compared to the DDL Driver. What is the driver doing exactly? Other than supplying the diode with an ideal, steady current and voltage. I suppose I should do more research on the LM317T and what it does.

Thanks again!

a_pyro_is · Jan 20, 2008

MTG18, I have a very long post earlier in this thread, as well as one linked to in another thread I've posted in this morning explaining why that won't work. If you're having trouble finding it just PM me and I'll direct you to it.

jaap75 · Jan 20, 2008

Hi guys,

Here are some pics like you asked for

-
-
-

Normaly erverything is insiolated, but i took the elektrical tape off so you can see it better.
Gazoo was right about the battery's, only 5,69v together and both 2,84v saperated.
But I don't understand why the voltage is so low, because I used them beraly since I checked the voltage for the last time.
I guesse it's just some crap the dealextreme sells.

I also bought these batterys fram dx:
-

They are rechargeble so when thier fully charged they give off about 3,6v so I build this thing.
-
This makes a controlled discharge possible.

I'll check if everything works when both batts are 3.0v.

Greets. Yoeri

Ps. I tried to post images, but it gives an error that i dont have the promission to post links. ( all my url where between

)

How can i post pictures? Let me know please.

member02 · Jan 20, 2008

you need more post before you can show pictures, send me a pm and i'll put them her for you.

amkdeath · Jan 20, 2008

just do it like this:

h ttp://www.whatever.com/yourimage

put spaces between the h and the ttp

regards,

amk

member02 · Jan 20, 2008

these are his pictures:

Skram0 · Jan 20, 2008

amkdeath said:
there are also other options, like the fusion drives, going for $4 ea + 1.50 shipping in the group buys section

those work with bluray and red diodes, and fit in your axiz housin, and are VERY TINY

I'm trying to figure how the fusion drivers can fit in an AixiZ housing. His dimensions are "0.693" by 1" or 17mm by 25.4mm". But the free space in an AixiZ housing is 0.41" by 0.75" or 10.3mm by 19.1mm and that doesn't count the leads of the diode. I'm thinking of getting a couple to see anyway, but I wouldn't think it'd fit in that housing unless the ones I have are much smaller than the norm. :-?

DIY Homemade laser diode driver

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