DIY Homemade laser diode driver

Sunny said

confused all these variation of pots, resistors, and capacitors

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The capacitor needs to be 10microfarrad 16v
The pot should be 100ohms max
The resistor you need to work out for yourself. It will set the maximum current available to the LD, use search to find the max current then go to the driver page on my website (link below) use the simple sum to work out your fixed resistor.

Momo said

It would be nice if someone could explain the WHOLE THING about making these into flashlights.And i mean EVERY little detail

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There are very good tutorials on here that take you step by step through flashlight builds, you need to spend some time looking for them.

DBTR said

Ive set up this driver to a 'T' and when i hook up the pre-installed diode I get a very faint glow. However, when I hook up a diode that i extracted from a DVD burner to the exact same driver, it shines brighter than something I would want to look at

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My guess is that the pre-installed LD is dead, swap it with the one you know works....remember to short the cap before removing and adding LD's though.

Regards rog8811

Bummer.. That could have been cuz I forgot to discharge the capacitor the first time I tested the Diode... Well, looks like I have to do the ol' switch-a-runny. Thanks for the info.

Just because I am an idiot, can this be used with a 9v batt?
Also, what resistor value would I need in place of the pot to get 400 mA?
</noob>
Nevermind.... I just found Rog's websote. Very helpfull.

Hello again, i wondered what to do with few IR diodes i found in scrapped dvd burner sleds.. they are all 48x CDR and 32x CDRW.. what is the max currentage for these for them to max their optical output and actually not die in weeks.. i was searching for the info at rog8811's site, but eventually i failed. this forums' search didnt help me at all as it spit out only thousands of useless posts.

Hello All, I am new to these forums, but not new to laser building... I have built a few 200mA red lasers before and they were all very simple resistor-capacitor smoothing and this guide for building regulators was the most helpful I have ever seen anywhere.... I am about to construct a very powerful 2 watt IR laser (no I am not some idiot who is about to burn his eyes out, I already have proper eye protection because I like my stereoscopic vision and intend to keep it) and I need to construct a proper regulator as the diode was quite expensive. My question is: Can LM317's be set up in a parallel configuration so as to allow currents approaching 3A? Second off I was wondering if it would be beneficial to add a bleed resistor in series with the capacitor to make sure that the capacitor drained all of its charge when the unit was shut off? this could be useful if one were to be using this regulator with multiple diodes as you wouldn't have to go to the trouble of shorting the cap. before each switch out of diode. Lastly I have recently found that one of my favorite sites, United Nuclear, will soon be selling the most powerful lasers I have ever seen!! They aren't diode lasers but VERY high power IR CO2 lasers available from 40 WATTS TO 100 WATTS!!! http://http://www.unitednuclear.com/deathray.htm Of course they are quite expensive, and almost insane... FOR THOSE OF YOU WHO DON'T KNOW HIGH POWER IR LASERS ARE[/SIZE] EXTREMELY DANGEROUS YOU CANNOT SEE THE INFRARED LIGHT BEING EMITTED FROM THESE LASERS AND THEREFORE YOU CAN BURN OUT YOUR EYES BEFORE YOU EVEN REALIZE THAT THE BEAM HAS BEEN REFLECTED IN YOUR DIRECTION DO NOT EVER WORK WITH IR LASERS WITHOUT PROPER EYE PROTECTION!!! Sorry for the public service announcement but I felt that it had to be said

regarding the diagram

as I understand it...
6V in, dropped 2V through the 317 = 4V
317 [assumed pot = 0] output current is 1.25/4 = 312ma, if [pot is 100] then 1.25/104 = 12ma


What is the purpose of the 1N4001?
why not a zener?

And for choosing capacitors, is there was way to calculate precisely what value to use?
At high frequencies, using solid tantalum caps would suffice with less capacitance compared to radial electrolytic.

Is a 0.1uF solid tantalum not needed in this case on the input end?

The purpose of 1N4001 in a standard DDL driver is to provide reverse polarity protection.
Zener diode would not protect from this as it can allow current flow in reverse as well.

When selecting a capacitor the main thing is to chose one that allows some buffer in maximum voltage. In other words if your max circuit voltage is 10v I'd go with at least a 16v cap. Secondly I almost always use tantalum caps with laser diodes as they are lower noise. The capacitance rating in a DDL driver is not an extremely critical value a 47 micro farad (µf) or 100 micro farad will suffice. I hope I could help a bit. Happy lasing to you!

Here is the smallest DDL I've been able to come up with using a standard LM317T. Fits right inside the back half of an axiz module, works great. Simple and reliable!

rog8811 said:

@Daedal, Thankyou for doing that...I have just ordered some regulators.

When it comes to other components I assume that a 200ohm pot would suffice? Will any signal diode do, I have a shed load of 1N4148's.

This next question will really show my ignorance.....But, if this circuit were to be tested on a standard led (rather than the precious laser diode) would the charecteristics, IE current draw, be anywhere near similar?

Regards rog8811

*Hope the mods stick this in the sticky area with sticky stuff...I will be stuck when it falls down the page *

*edit....years after posting this, and having built dozens of these circuits.. easy to follow picture follows

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Does this schematic work with blu ray laser diodes??? or to u need a pot with blu ray diodes??

100K-Ohm Horizontal-Style Trimmer
would this work for a pot ???

dtucker21 - 100k pot is not suitable. This is way too high of a resistance. The pot should be less than 100 ohms, a 25 or 50 ohm used with a fixed resistor to set max current would be more appropriate

The DDL driver will work fine with blurays, you will need at least two, if not three lithium cells in series as the LD drops about 5.5V and the driver needs a good 2V overhead in order to regulate. To make a smaller driver, substitute an LM1117. To make a more powerful driver, substitute an LM350 (3A max) or an LM338 (5A).

Hope this helps ...

For me the coding is messed up in the original post. Some of the parts list links are invalid too. Is their any ways we could get an update on this?

rog8811 said:

I had too much time on my hands today...new picture of DDL circuit coming up....

Regards rog8811

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Rog8811,

What is the max safe operating params of this circuit? I built one out on a radio shack protoboard just added an on off toggle switch and soldered it all together last night .. attached a red LED first and powered it up with 6 AA batteries (alkaline as my NiMh were dead) and worked out fine.

Rotated the trim all the way down to the point of lighting the LED and then attached a 632nm RED dvdrw harvested LD. powered up , carefully monitoring the un-heatsinked LD temp and slowly turned up the trimmer until it visually appeared at its max (uncollimated - unfocused as its easier to determine visually). The duty cycle rarely exceeded 10 secs for testing and once it seemed safe i marked the trimmer position and put the LD in a copper block i had that magically somehow was a nice snug press fit by hand.

Question to this long painful explanation is that Id like to use a 7.2V AC Adapter to feed the driver , but I have several options around the house 500mA , 1200mA and ~2000mA .... are these safe to use to power the circuit?

Seems to be working pretty well

Well I figured I'd do a barn burner run on the driver/LD combo and see what I was reading ...

With 6AA 1.2 Alkaline's :
200.9 mA
2.75 V (drops fast... Alkaline's?)


With 7.5V 1000mA AC/DC adapter:
202 mA
2.75V


I'm measuring before and after the LD like this:

LD => (DVM -) =====> Driver

LD <= (DVM +) <===== Driver


Any thoughts? The LM317T does get surprisingly hot though! lol

nice one Daedal, now thats what i needed some one to spell it out for me!! now i`ll have a go n build a driver . cheers agian!!!!!!:drool:

thanks for all