Another "OH GOD I'M BUILDING A LASER WHAT" thread

[Kyosama66]

Well, I'm looking into building a laser. My problem is that I have a pretty good amount of Amazon gift card credit stuck on my account, and nothing else to really grab, so I'm hoping to source as much as possible from there. So far, I've got the following components:

Module
Diode
Driver

I plan to power it from 18350's and put it into a small form flashlight housing I've got. My question is really this: Will these parts work together?

Also, any hints or suggestions are very welcome.

 

[Sigurthr]

That is an 808nm IR diode, and that driver is a boost driver intended for 445 and 405nm diodes which require a much higher voltage. I don't know if that driver can support a low Vf diode (it probably can't).

I suggest you find yourself another diode, 808nm is near-invisible for most people, and exceptionally dangerous.

 

[Kyosama66]

That is an 808nm IR diode, and that driver is a boost driver intended for 445 and 405nm diodes which require a much higher voltage. I don't know if that driver can support a low Vf diode (it probably can't).

I suggest you find yourself another diode, 808nm is near-invisible for most people, and exceptionally dangerous.

I do recall reading something about 405 and 445 needing higher voltages now that you mention it. I'm not set on the 808, since I know it's difficult and/or dangerous to work with, I was just looking for the maximum power for what I was paying.

My new question is this: What determines the driver's power? is it a current thing? I'm trying to read up on this as much as possible before I start cooking diodes and wasting money, but sometimes you just gotta ask :thinking: For example, could I use, say, This 405 diode, since it's rated at 150mw instead of 1W?

I'm starting to guess it's not possible to build an entire laser off of Amazon

 

[Sigurthr]

Well you have two very important numbers you need to match up when matching a diode to a driver (and picking the right ones of each).

1) Vf - "forward voltage" - this is the minimum voltage the diode needs to operate. Exceeding it by about 1v is generally not harmful and sometimes beneficial as long as you have adequate heat sinking. There are also two very important attributes you need to keep in mind.

2) Current - diodes put out more light the more current you supply them, but they have a minimum current and an absolute maximum current. Below the minimum current, called the Ith (Big I, little th) or Threshold Current, no lasing occurs. If you exceed the maximum current, the diode will be fried.

A) Diodes require a CONSTANT CURRENT driver. This means that the driver supplies the current it is set to, and lets the voltage sort it self out.

B) Drivers have what is called a "drop out" voltage. This is the difference in voltage between what you put in to it and what you get out of it. For example, a "DDL" LM317 driver has a drop out of 3V, so what voltage comes out of it is 3V lower than what you put in to it. For example if you wanted to use it to power a diode which has a Vf of 3V (like a typical red diode) you would need to input 6V to the driver to get 3V out. Low drop out drivers are called "LDO" drivers, and the actual drop out voltage varies from type to type as well as dependant on how much current they are set to.

*Buck/Boost drivers take a low voltage but high current input and put out a high(er) voltage and constant current output. A buck/boost driver like the Flexdrive could take in 3.7-4.2V from your Li-Ion battery and turn it in to the 4-6.5V that a 405nm diode would need. These drivers don't effectively have a voltage drop out, but they do require a very strong current source (battery).


As far as will that 100mW 405nm diode work with that "1W 445nm" driver... it depends on how low you can set the driver's output current. The voltage output from the driver should work fine, so it is all dependant on the lowest current the driver is capable of being set to, and if that current is within the range the diode accepts.

 

[Kyosama66]

Well you have two very important numbers you need to match up when matching a diode to a driver (and picking the right ones of e.......

Perfect! Now I know! It looks like that diode only runs up to 150mA, where the driver puts out 1100mA, so that's not going to work. I think I'll try to find another supplier for a 405 diode closer to that range.

Thanks for the help!