Does my LM317 driver need a test load?

[byerlyfactor]

Hi all,
Inspired by styropyro I am building a red laser pointer. For the driver circuit, I plan on using an LM317 with a few filter capacitors and a reverse protection diode. According to an online calculator, I need a 1.6 ohm resistor to drive my diode at 800ma. Do I need a test load to set the current? Thanks in advance for your help.

 

[Giannis_TDM]

Hi all,
Inspired by styropyro I am building a red laser pointer. For the driver circuit, I plan on using an LM317 with a few filter capacitors and a reverse protection diode. According to an online calculator, I need a 1.6 ohm resistor to drive my diode at 800ma. Do I need a test load to set the current? Thanks in advance for your help.

Since you are not using anything complicated you don't really need a load just check your wiring and upload a pick to LPF so we can also double-check for you, Although you do very much need a heatsink. Also what laser diode are you driving at 800mA??!

 

[byerlyfactor]

Since you are not using anything complicated you don't really need a load just check your wiring and upload a pick to LPF so we can also double-check for you, Although you do very much need a heatsink. Also what laser diode are you driving at 800mA??!

Thanks for the reply. That is good to know about the heat sink. I’m using a half watt 638nm eBay diode.
ebay. com/itm/174116499606
The datasheet calls for a max of 800ma but I may use a larger resistor at first since the recommended current is 650ma.

 

[Encap]

You are going to need a module and a lens in addition to a heatsink unless all you want to do is light up the bare diode for a second or two--see https://sites.google.com/site/dtrslasershop/home/diodes/mitsubishi-635nm-500mw-diodes

You also need laser goggles/glasses to protect your eyes

 

[Cyparagon]

Your 1.6ohm is already acting as current-sense. Use that. Ohm's law.

Test loads are typically for verifying an unverified setup. LM317 in CC is about as opposite from unverified as you can get.

On the other hand... One other use is to verify you wired things properly.
On the third hand... but this circuit is so simple I don't see how you can fuck it up.
On the third leg... yet I've seen many people absolutely fuck up a 2-component driver before, so I guess it's up to you.

 

[byerlyfactor]

You are going to need a module and a lens in addition to a heatsink unless all you want to do is light up the bare diode for a second or two--see

You also need laser goggles/glasses to protect your eyes

Of course, I bought some goggles from survival laser. And a 20mm module from DTR which doubles as a heatsink. And for the other stuff I have most of it ordered but for some I have to wait for shipping from China. So I will post a build thread when I have everything.

 

[byerlyfactor]

Your 1.6ohm is already acting as current-sense. Use that. Ohm's law.

Test loads are typically for verifying an unverified setup. LM317 in CC is about as opposite from unverified as you can get.

On the other hand... One other use is to verify you wired things properly.
On the third hand... but this circuit is so simple I don't see how you can fuck it up.
On the third leg... yet I've seen many people absolutely fuck up a 2-component driver before, so I guess it's up to you.

Thanks. I'm not new to circuits so I think I'll do fine lol. I'll just measure the current across the resistor before I hook up my diode.

 

[WizardG]

Thanks. I'm not new to circuits so I think I'll do fine lol. I'll just measure the current across the resistor before I hook up my diode.

Ummmmmm........you don't measure current across a resistor. That would be one way to fuck up a 2 component driver.

 

[byerlyfactor]

Y

Ummmmmm........you don't measure current across a resistor. That would be one way to fuck up a 2 component driver.

Yes I know you put the multimeter in series with component

 

[thanhtung]

You can use caculator
I(A) = 1.25/R(ohm)
You need know exactly how many max current of your diode can run then use that form caculator without not need testload

 

[Alaskan]

Inspired by Styro! I'm miffed at that guy for making such dangerous lasers and plastering it all over YouTube scaring the public what laser hobbyists can legally do, that rat faced guy is going to get our hobby outlawed, wait until I make a bigger badder more dangerous one for my YT channel!

 

[Unown (WILD)]

You should see his discord. It's a total worship fest.

 

[Giannis_TDM]

You should see his discord. It's a total worship fest.

Are you saying that because you got banned for swearing at members in a voice chat after you rejoined because you were banned before that but got unbanned as a second chance?

 

[Unown (WILD)]

Are you saying that because you got banned for swearing at members in a voice chat after you rejoined because you were banned before that but got unbanned as a second chance?

As I said before kid that voice chat never happened but no that's not why I said that. I said that because it's a total worship fest. Perhaps you're the one upset because you're a mod there or maybe you just want to start an argument which I have no interest in but go ahead and keep trying.

 

[Giannis_TDM]

As I said before kid that voice chat never happened but no that's not why I said that. I said that because it's a total worship fest. Perhaps you're the one upset because you're a mod there or maybe you just want to start an argument which I have no interest in but go ahead and keep trying.

You can say all you want but our logs say otherwise, And no being a mod there doesn't affect any decision of mine. It just makes me more unbiased because I have access to all logged actions. And no, Not looking to start an argument. Just stated a fact. Continue your rant about that discord being a worship fest as normal.

 

[Unown (WILD)]

You literally are looking for an argument because you saw something you didn't like on the internet. There is no way to "log" a voice chat unless you record it and since it never happened there is no audio recording so go back to the little hole you live in. Don't you have drivers to work on?