Newbie needs help

[leslieliang]

I'm an airsofter and wanted to make a custom PEQ laser box for my gun with 5mW lasers. I've known that DX sells lasers, but me, being a person that doesn't buy anything without doing extensive research and asking a lot of questions, decided to look for a laser forums, which led me here. I've read the stickies and such, but still don't really understand. So here we go with the question.

What is the difference between a laser module and diode?

What exactly does the voltage represent?

Are the voltage and milliwatts of a laser related? I was looking at 5mW lasers and saw that some were 3v while others were 5v or some other number.

Why do some laser modules have a PCB while others don't?

 

[Morgan]

Check out the links in my sig below. They are guides to building your first laser. You may not want to do this but it explains a lot of the stuff you are asking about.

About voltage... No, this more relates to the wavelength a particular diode outputs. ~2V - IR and NIR diodes, ~2.5V - Red diodes, ~4V - 445nm/Blue diodes, ~5V - 405nm/Violet or, 'Bluray', diodes.

Also, don't forget to introduce yourself in the, "Welcome", section and tell us a little more about yourself.

Oh, and welcome to LPF! :wave:

M

 

[horhay]

are you doing green, like the video?

a laser MODULE if youre talking green is pretty much the whole laser minus a battery and something to put it in. for a first build, thats the way to go

a laser diode is like, say, a flashlight bulb. you still need lenses, a driver to give it the right power, etc. for green it gets crazy complicated, since its DPSS (IR laser goes through some crystals that flouresce green, to put it EXTREMELY short). green diodes dont really exist for common consumers. yet.

a laser module can be two things- a fully put together module with circuitry, like you see on DX, or an aixiz module, which is just a housing for the diode (looks like a silver metal cylinder with lens). is that what youre referring to?

 

[leslieliang]

So generally, a laser module is a laser diode with the cylinder, the filters, and the PCB (driver?), right?

I'm planning to have both red and green lasers in my PEQ box, but not planning to build a laser (although those threads were really good info). I want to buy a prebuilt laser module and just make a "host" for the laser with the PEQ box.

The voltage thing is still kinda fuzzy to me, especially after reading the guide in your sig. What is voltage drop? Is it the voltage listed in the product's name on DX? Why do red lasers have 3v and 5v variants?

Do the red laser modules sold on DX have a built in driver because some have PCBs on them while others don't? If yes, how do I find out if it's a linear, boost or combo?

What would happen if I used a 6v battery on a laser module rated at 3v?

 

[horhay]

right. all the green modules on dx have everything included.

green is about 10x (or more) brighter to the human eye than red... so if youre trying to balance them, youre gonna want to look up using an LPC-815 sled diode. its a good first build, but youre gonna have to read up a LOT. (A LOT).

5V? im not sure where you got that... red lasers are typically 2-3V.

red laser modules on dx probably have a circuit, but i dont know for sure. pcb's are drivers. laser diodes are REALLY sensitive (Ive learned that the hard way ) so they need a really constant current, which is supplied by the driver. a normal battery will have small voltage spikes that will kill the diode. there are a couple diodes, like the aformentioned 815, that i've been able to get by without a driver- just a resistor and a capacitor- but with small batteries.

to answer your last question... something like this
:lasergun:
j/k. it would die

 

[Morgan]

Sorry horhay, but a resistor and capacotor will not do. Look up the simplest driver here using the LM317 voltage regulator. It's setup in our use as a constant current regulator. Using a resistor and capacitor may work on paper but you need more than that.

Regarding the voltage thing. Each diode of a particular wavelength requires a different forward voltage, (look up diode forward voltage). For our purposes, for instance with the LM317, the voltage is taken care of. It's the current you really need to think about. This being said, when a complete module is being sold and the specs are given then your supply needs to be able to give that voltage. Modules you have seen on DX saying they require 3V will need to supply 3V. Commonly the components used on this type of driver board will accept more voltage, (and output more light!), but will kill your diode.

To understand this more you need to know the difference between, 'constant current', and, 'constant voltage', regulators. Read through the first guide again, there are a few videos in there that should help.

It's a slow process knowing just what's going on but you'll see that the specs on almost all the green, (532nm DPSS), modules you see will state an input voltage of 3-3.7V. My advice for long life would be to not feed them more than 3V. Remember that current is drawn BY a device, not fed FROM a device.

M

 

[horhay]

morgan- i have built many lasers and i understand the need for a driver. i'm just saying that the LOC-815 diode is very robust, and can handle a couple AA's with a resistor and a cap. ive done it several times- the second laser i ever built was this design (trying to cut costs) and it still works at around 200mW. i have also built many DDL drivers, which work for essentially everything else. i never use a resistor/capacitor with li-ion batteries. its not optimal, but this diode can get by with it. i understand these things i just cut corners when i can

 

[leslieliang]

So I just got into a huge discussion with my friends about voltage, amps, and watts. What are the differences between them? Why do some light bulbs need different voltages, but have the same wattage? And why do some light bulbs need similar voltages, but have different wattages?

I am planning to make it so that 2 lasers and a led will share the same battery. My friend told me that according to V=IR, sharing a battery between 2 lasers and a led will make the current drop for each device. Is that true? Or will the drivers make the current correct?

Also, the drivers that come with laser modules on DX are CC drivers right? It will keep the current constant, but will change the voltage if needed, right?

That brings up another another question. Does more wattage = brighter laser? Does more voltage = brighter laser?

I thought I knew some stuff about lights and voltages, but I guess not.

 

[horhay]

watts is amps x volts. imagine it like a river: voltage is the speed of the river, current is how big it is. therefore watts is how much power is being used at one time. so a light bulb with the same voltage with a much higher wattage as another would have a larger current. laser diodes, when given the chance, will take the right amount of voltage- but not the right amount of current.

putting them in parallel, the current would only drop if your battery could not supply enough current. if it can, then sure- make sure you put a resistor on that LED so you dont kill it with the same current as the lasers.

i'd assume so- controlling both volts and current is pointless. they will not change the voltage, other than lowering it through inneficiency- so don't go plugging too many volts into one.

a diode that can handle more watts can be run brighter. a 5mW diode will not produce 100mW when pumped with more power- it will die. more voltage means a higher wavelength, due to things i can't really describe. but as morgan said before, Red ~ 2.5V, blue ~4V, violet ~5V, although more high-powered ones draw a bit more voltage.

hope this helps

 

[Morgan]

morgan- i have built many lasers and i understand the need for a driver. i'm just saying that the LOC-815 diode is very robust, and can handle a couple AA's with a resistor and a cap. ive done it several times- the second laser i ever built was this design (trying to cut costs) and it still works at around 200mW. i have also built many DDL drivers, which work for essentially everything else. i never use a resistor/capacitor with li-ion batteries. its not optimal, but this diode can get by with it. i understand these things i just cut corners when i can

What you say here is not inaccurate just a very risky thing to do. From some sort of bench power supply or similar it may be perfectly adequate but most of the builds here are for portable use and therefore rely on batteries as a power source. This being the case it is not usual to advocate the cost cutting method. Yes, we know it works, but no, it's not the BEST solution. We always look for the BEST solution because there is pride involved. If we don't, we are no better than a cheap Chinese manufacturer. No malice here but do you understand why it's best not to even mention the cheap method?

M

 

[horhay]

as a beginner, he should know that if he does that build, there are options. i remember soldering my first LM317, it was a nightmare for someone without any circuitry background! (at the time anyway) besides, who wants to carry around extra batteries for the LM317's voltage drops? some vets here have even done direct drives like this, all with small batteries. its still an OPTION if he's going to go with THAT particular diode. i didnt come into this hobby to be any better than chinese manufacturers, in fact, i'd like to see someone here to get homemade DPSS that small j/k. i understand your point but i think this is a pointless and stupid argument to be having, as it doesn't really help anyone- we both understand building lasers, just from different perspectives. so why not leave it at that? from what he's saying, i think he's buying the modules with the drivers anyway.

 

[leslieliang]

Ahhh. Now I'm just super confused. Let's just say I want to get a 5v green laser module, a 3v red laser module and a Cree LED from DX and hook them all up to the same battery into a PEQ box. Would I need any drivers, resistors, circuits, etc.?

 

[Morgan]

Agreed, but...

Beginners to building lasers, in particular, should be giving the best direction. The best direction is to go the proper constant current route. This means more than resistor and capacitor route, (i.e. the cheap ICs available). Otherwise we should just accept that the Klipklay route is satisfactory and I think all here who know their stuff would not recommend that.

For the most part, those that have direct diven their diodes have done so knowing the particular diode they are using has been unusually sturdy, such as the new 445nm diode. There are few that have used the run of the mill diodes in this fashion and, if they have, have reported that this has it's risks. For a beginner these risks, are more likely than not, unacceptable.

I think we agree, in principle, but please do not think that the forum will change their opinion on this. As a beginner there are options but the cheap one is not the best and we should not be promoting it. If something goes wrong, and he loses a diode because of it then whoever suggested it is responsible. As such, and as a forum, we would not recommend the resistor and capacitor route.

A 532nm DPSS module should run from a 3V battery source, such a 2 x AA batteries, quite reliably however. As long as it comes supplied with a driver board, (most are), and depending on the quality of the module purchased.

M

 

[horhay]

i think its questionable whether or not 2xAA's can supply enough current for all three. what batteries are you planning on using? you'd need a resistor for the LED any way you go.

 

[leslieliang]

i think its questionable whether or not 2xAA's can supply enough current for all three. what batteries are you planning on using? you'd need a resistor for the LED any way you go.

I'm thinking of getting CR123A or CR2.

What exactly does the resistor do?

I'm trying to do something like this. Can you guys help me draw up like a schematic and tell me what parts I'd need to do that?

 

[Morgan]

i think its questionable whether or not 2xAA's can supply enough current for all three. what batteries are you planning on using? you'd need a resistor for the LED any way you go.

All three what? It's just one laser we're talking about here isn't it?

3V for a common-all-garden 5mW, green DPSS laser module with driver board attached is fine. No schematic necessary, most come with a simple +ve and -ve connection that you need to join to a battery pack you can find in any electronics suppliers. There will normally be a momentary switch on the module you buy so perhaps some modification needed there but the battery pack will be easy to find. 2 x AA will almost be the first thing you come across in the store when you ask. Trust me.

M