Building a High-Power Laser Headlamp: A Step-by-Step Guide

As I begin to dial in the current on my multimeter, I'm excited to see how this tiny driver will perform. The potentiometer is set up to allow for precise control over the output current, and I've double-checked that all polarities are correct. With 81 mA, the LEDs are already lit up, giving me a sense of confidence in the driver's ability to deliver high currents.

To test the laser diode further, I'll reset the driver to minimum settings and power it on. The goal is to see if this tiny driver will be able to deliver 3 amps. As I watch the current climb, I'm impressed by the potentiometer's precision - these things take a lot of turns! With a final reading of around 4 volts, I'm satisfied that the driver can indeed handle the required power.

With my laser diode and driver in place, it's time to assemble the headlamp. After following my step-by-step guide and getting a feel for the current adjustment, I'm ready to power up the laser headlamp. One final precaution is taken - laser diodes are extremely sensitive to electrostatic discharges, so I'll be careful when attaching the laser and ensure that any remaining charge in the output capacitor won't dump too much unregulated current into the laser.

With my static-free workstation and laser safety glasses on, I'm finally ready to power it on. Will it work? Oh yes - even at lowest driver setting, I'm seeing white light! The laser is shining its blue light down on a phosphor that converts some of it to other colors of light, creating a beautiful display.

However, as I continue to experiment with the headlamp, I realize that the power output is significantly stronger than I anticipated. With an estimated 3900 milliwatts, this laser is almost 3 times stronger than my Arctic laser and almost 8 times stronger than the threshold for Class 4 lasers - the highest risk class. This is a much more powerful device than I initially thought.

To confirm the power output, I'll measure it on a laser power meter. To access the laser beam, I need to remove the bottom plate with the phosphor on it. Using a Torx T6 bit, I carefully release the tiny lock washers and lift off the plate. The laser beam is reflected straight down onto the phosphor by a mirror placed at a 45° angle in front of the laser aperture.

As I prepare to take my first measurement, I'd like to take a moment to talk about a more advanced piece of electronics for measuring high-energy photons - the Radiacode radiation detector. This tiny device is packed with features that old-fashioned Geiger counters can only dream of. Not only is it a detector and precise dosimeter, but it's also a gamma spectrometer with isotope identification capabilities demonstrated in an earlier video.

Another feature of the Radiacode is its radiation mapping capability - when paired with your smartphone, it can map the radiation levels on your path, revealing exciting radiation sources like granite buildings and tiles or special uranium glass and glaze in thrift shops. This technology adds a whole new level of excitement to what might otherwise be an ordinary travel experience.

For more information on the Radiacode radiation detector, I recommend checking out their website with the promo code "video" included.

"WEBVTTKind: captionsLanguage: enHi!This is a crazy headlamp for a car.Its light source is not a halogen bulb or an LED.It is a laser!In this video, I will take a closer look at howthis beast works and how to make it work.After figuring out how to power its sensitive laser diodeI will measure its optical power output.How strong is this laser meant to be put into a car?Let's find out!When experimenting with a laser, wear safety glassessuitable for its wavelength and power output.And never look directly into at a high-power LED or LEP.This headlamp is sold on eBay without any power supply.So my first challenge is to find a suitable driversince laser diodes are very easily damaged.Would be sad to destroy a 69 dollars light within seconds.Luckily, the listing came with some clues on how to power it up.It uses a 450 nm laser at the border between indigo and blueand can handle up to 3 amperes.Quite a lot of amps for a single diode.But I found this driver board that will deliver aconstant current of up to 4 amps to a blue laser diode.Nice.However, I have never bought a laser diode anddriver separately and matched them up.How do I make sure this driverwill not deliver more than 3 amps?To get some hands-on experience, I will take it step by step.The issue is laser diodes have a bad behaviorcalled negative temperature coefficient.In short, they decrease their resistanceas their temperature increases.This will lead to a destructive thermal runaway whenthey draw more and more current as they heat up.The best way to stop this vicious circle,is to use a constant-current power supply.Limit how much current the laser diode is allowed to draw.Alright. First step in my neededhands-on experience will be a simple one.Set up the multimeter to read a current of 3A DCand adjust a constant-current power supply to 3A.As a dummy load, I will use a resistor with around thesame resistance as the laser headlamp run at max.I will not limit the voltage, I will only limit the currentand let Ohm's Law take care of the rest.There we are. The circuit is now set to 3 ampswith milliamps precision without blowing anything up.But this was way too easy.Unlike a laser diode, this resistor doesnot have an NTC or electrical polarity.Next step in the challenge is to use light emitting diodes.Just like laser diodes, they do havean NTC and electrical polarity.This mess is four high-power LEDs wired in parallel.Each LED will handle 750 milliamps so- in parallel - they can handle 3 amps in total.Perfect.After double-checking correct polarity, + to +,and setting the power supply to constant currentlet's see what 3A will do to this circuit.Okay. They are already getting bright.I will diffuse them to spare my eyes and camera.Success!The LEDs are fully powered up under conditions that are verysimilar to what the laser headlamp needs to run at full power.The power supply is providing 4.1 volts to the circuit.You might think it is a bit high for LEDs listed as 3.2 to 3.8V.But I am not worried, because the current is right for the LEDs.And there is a voltage drop across themultimeter - known as burden voltage.The forward voltage across the LEDs is not the full 4.1V.I can simply show it by removingthe multimeter from the circuit.This time with glass for a welding maskover the LEDs to see all of them light up.3.8V - within specs.Makes sense the voltage is at the high end,as there is plenty of cooling for the LEDs.Keeping them cool, keeps their resistance at their high end.Which in turn means a higher voltage isneeded to push 3A through the circuit.At this point, it is tempting to justreplace the LEDs with the laser.But laser diodes are way more sensitive than LEDs, and thisswitch mode power supply does not deliver a clean current.Switch-mode is inherently noisy with ripples in the output.I don't trust this power supply to safely run alaser diode - especially at start-up and shut-down.This is where the laser driver board comes in.It is designed to deliver laser-friendly electricity.The driver will run on anything between 9 to 12 volts DC.I could use a battery, but I alreadyhave a power supply on the table.Just need to change it from limiting current to limiting voltage.I will set it to max 9 volts.Should be plenty enough as the driver board only needsto output around 4 volts to the LEDs or laser headlamp.Before hooking up the driver board,I have dialed its current limiter all the way down.I am using a trimmer tool since it is sleeved.Making it less likely that the toolslides off and short-circuit somethingwhile I am looking at the multimeter to dial in the current.The potentiometer does not seem to have a hard stopbut it starts ticking when dialed all the way down.After making sure, I got all the polarities rightit is time to test the driver.Great start. At 81 mA, the LEDs are already lit up.Time to see if this tiny driver will deliver 3 amps.Hmmmmm.Did I break it already?Nope. The current is climbing now.This type of potentiometer really takes a lot of turns.Useful for higher precision.Nice. This will deliver 3 amps at around 4 volts.Time to test the laser.After resetting the driver to minimumand after this short message.A big, BIG thanks to all my patrons!I appreciate your help with keepingniche videos like this one coming.For just a dollar a month you can help me out tooand get full access to all my posts on Patreon.comLink in the description.Thank you!Okay. After having built up a proper setupstep-by-step and getting a feel for the current adjustmentI am ready to power up the laser headlamp.Only one more precaution to take care of.Laser diodes are destroyed by electrostatic discharges.I will therefore baby the headlamp at a static-freeworkstation until I have it connected.I will also make sure the driver does not haveany remaining charge in an output capacitorthat would dump too much unregulated currentinto the laser once connected.Good - no charge remaining.I will attach the laser while making sure + goes to +.With laser safety glasses on, I am finally ready to power it on.Will it work?Oh yes. Even at lowest driver setting,I am already seeing white light.The laser is shining its blue light down on a phosphorthat converts some of it to other colors of light.This is known as LEP - laser excited phosphor.Let's give it some more juice...Oohkayy... I am not sure this is good for my camera's sensor.Let me diffuse the light.Wow. This is intensely bright.Hard to see on the overexposed camerabut most of the light is in a tight, bright beam.How strong is the laser in this headlamp?Definitely stronger than mytemporary cooling solution can handle.I need to find some M2 screws toadd heatsinks to the back of the lamp.For short runs it is fine though.To double-check I am running the laser diode within specsI measured the voltage from the driver.4.3V including the multimeter driven in series.That is fine.The power loss in the driver is around 3 watts.A small cooling fan on the heatsink might be a good ideafor long runs once I have proper cooling on the laser diode.Regarding power, the specifications do notmention the optical power output of the laser.I believe there are some hidden clues though.Suggesting a laser around 3900 milliwatts.Really? That's a very, very strong laser.Almost 3 times stronger than my Arctic laser?Almost 8 times stronger than the threshold for Class 4 lasers?The highest laser risk class.I must be reading the specs wrongly.Well, only one way to find out.Measure it on a laser power meter.To gain access to the laser beam, I will removethe bottom plate with the phosphor on it.A torx T6 bit will do the job.There we go.Don't lose the tiny lock washers.Even though they are magnetic in case youneed to find them on the floor like I had to...The laser beam is reflected straight down onto the phosphorby a mirror placed at a 45° angle in front of the laser aperture.Some laser power will be lostto this mirror in the optical path.A first-surface mirror will reflect around 95% or so.Only a 5% loss but worth keeping in mind.Now, before the final test, I would like to tell you abouta much more sophisticated piece of electronicsfor measuring high-energy photons,made by the sponsor of this video.This is the Radiacode radiation detector.A tiny device packed with features that old-fashionedGeiger counters can only dream off.Not only is it a detector and precise dosimeter,it is also a gamma spectrometer with isotopeidentification as demonstrated in an earlier video.Another feature is its radiation mapping.When paired with your smartphone, the Radiacodecan map the radiation levels on your path.You might discover exciting radiationlevels on your walk or shopping trip.For example from granite buildings and tiles or thatspecial uranium glass and glaze in the thrift shop.Finding radiation sources can add some spiceto an otherwise ordinary travel.For much more information,I recommend you check out their website.Link in the description.Use the promo code \"Brainiac75\" to takeadvantage of a special offer from RadiaCode.Details are in the video description.Thanks RadiaCode, for making a differenceand helping out my channel.Now, back to the laser radiation.Alright. With laser safety glasses on andthe laser power meter calibrated for 450 nm,we will now find out if this isaround 3700 mW after mirror loss.That's a lot of photons!It peaked at 4,370 mW after mirror reflection.Likely 4,600 mW before the mirror.Wow!To make things even crazier, the listing saysthe 3 amps limit is not due to the laser diode.It is the phosphor that will give up firstif the laser is dialed higher.Astonishing!Click like if this laser excites youas much as me and the phosphor!In my next video, I will test this little gem furtherand compare it with a cheaper LED headlamp.Remember to subscribe and turn on the fullnotification bell if you don't want to miss that video.And comment if you have ideasfor further testing of the headlamps.In any case, thanks for watching.Bye for now.\n"