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 Laser Pointer Forums - Discuss Laser Pointers Alright got a 12x 405 and a M140 445... let's not blow them.

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04-30-2012, 01:55 AM #1
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Lucian
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Alright got a 12x 405 and a M140 445... let's not blow them.

Hey guys. I don't have a driver for my builds yet, so until my driver arrives I wanted to test my diodes anyways.

What I have readily available is a 12v constant power supply (and it is constant, no variance) capable of up to 2.5A of output.

I want to test the 12x 405 at 500mA.

Is it safe to put the power supply in line on my breadboard with a 24ohm resistor to test my diode?

500mA = 12v/24ohms correct?

---

I'm aware that math appears very simple and easy, but this isn't pocket change for me so I'm just trying to do everything I can to make sure. Thank you in advance for your help.

EDIT: I actually only have a 22ohm and 2 different 1ohm resistors available to test. Again I believe that won't matter but just checking
r1 + r2 + r3 = total resistance correct? 22+1+1 = 24?

Last edited by Lucian; 04-30-2012 at 01:57 AM.

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04-30-2012, 01:59 AM #2
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Impatience kills more diodes than poor skillz

Peace,
dave
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04-30-2012, 02:03 AM #3
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Driver won't be here for a while. It's being designed at the moment. But I just received the diode from shipment and don't want to wait a month or two before testing it and then trying to contact the seller if there is a problem.

While I completely understand, appreciate, and respect your advice daguin... I do need to test it to make sure its operational.

04-30-2012, 02:11 AM #4
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Hopefully someone will stop by soon to double check your math

Peace,
dave
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04-30-2012, 02:14 AM #5
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by daguin It's your diode Hopefully someone will stop by soon to double check your math Peace, dave
Yes sir. I'm waiting until it is checked lol. I seriously mean I appreciate the advice daguin. I've received nothing but kindness and helpfulness from the members here.

04-30-2012, 02:39 AM #6
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Couple things to consider here.

First that method you want to try is not something that anyone here would suggest to you.

Second diodes are always sold as is. So if they did not work after powering them with that method what would you expect to happen? I don't know a seller that would replace or refund you for it even if you said you used an appropriate laser driver and followed all safety precautions due to their sensitive nature of diodes and the multitude of ways they can be damaged. There would be no way for a seller to determine if someone killed the diode and was just trying to get something for free.

The only thing you can do is make sure you buy from a reputable seller with a track record of delivering tested and working diodes. I don't know if you got them from me but I am thinking you probably did and I don't want to see you loose your money.

I would heed the words of experience Dave was offering and wait for your laser drivers.

04-30-2012, 03:02 AM #7
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by DTR Couple things to consider here. First that method you want to try is not something that anyone here would suggest to you. Second diodes are always sold as is. So if they did not work after powering them with that method what would you expect to happen? I don't know a seller that would replace or refund you for it even if you said you used an appropriate laser driver and followed all safety precautions due to their sensitive nature of diodes and the multitude of ways they can be damaged. There would be no way for a seller to determine if someone killed the diode and was just trying to get something for free. The only thing you can do is make sure you buy from a reputable seller with a track record of delivering tested and working diodes. I don't know if you got them from me but I am thinking you probably did and I don't want to see you loose your money. I would heed the words of experience Dave was offering and wait for your laser drivers.
Yes I got them from you; and I did so because you have an excellent track record. But if they are powered up and never work (and done properly of course) then I will be asking my credit card for a refund because by the same logic as "The seller doesn't know the person isn't just scamming something for free(paraphrased)"... then "The buyer doesn't know if the seller just sent an already burnt out one knowing they wouldn't give a refund". I'm not accusing, and I'm sure you aren't either.... let's not make this something it isn't. I just said I wanted to test it since I just received it, if there is a problem it has to be reported right away.

Would someone please explain why this method would be unsafe? I'm not one of those people trying to argue my idea over and over against experience ... but I have yet to be given an answer as to yes the math is correct or no it isn't; and if no one would recommend it I'd like to know why so I can continue learning. I think its important someone understand why or why not instead of "just don't do it". I mean if I was just going to do it I would have right? I'm asking for help.

Lucian

P.S. Man I'm not saying anything... Of course I expect your products to work or else I wouldn't have purchased from you (Again for the track record :P). But the "No seller would ever give a refund" type statement came off as abrasive when I read it and makes me nervous since I Just spent >200 from you alone, not including everything else I've put together for the project so far.

Last edited by Lucian; 04-30-2012 at 03:24 AM.

04-30-2012, 03:26 AM #8
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

I can understand wanting to test them and I was trying to be somewhat blunt with you as it seemed you kind of dismissed Dave's advice.

I would work with my customers if they had issues but I wanted to be clear if someone came to me and said a diode that I sent out tested in working condition does not work the fist thing I would ask is what laser driver are you using.

The level I would be willing to work with someone is based on how comfortable I am with how they were using the items I provided.

Now I am not the electronic expert here and hopefully one will be along soon to give you a detailed reason why this is not generally used to power diodes but I believe the biggest problem with that idea is that there is no circuit in there that will restrict the current to no more than the appropriate level to power the diode even if the supply is trying to give it more. If you power supply has a voltage spike on start up what does that do to the math.

Last edited by DTR; 04-30-2012 at 03:27 AM.

04-30-2012, 03:43 AM #9
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

I have purchased from DTR before and he has never sent me a dead diode

Don't be impatient, wait for your driver.
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04-30-2012, 03:51 AM #10
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by DTR I can understand wanting to test them and I was trying to be somewhat blunt with you as it seemed you kind of dismissed Dave's advice. I would work with my customers if they had issues but I wanted to be clear if someone came to me and said a diode that I sent out tested in working condition does not work the fist thing I would ask is what laser driver are you using. The level I would be willing to work with someone is based on how comfortable I am with how they were using the items I provided. Now I am not the electronic expert here and hopefully one will be along soon to give you a detailed reason why this is not generally used to power diodes but I believe the biggest problem with that idea is that there is no circuit in there that will restrict the current to no more than the appropriate level to power the diode even if the supply is trying to give it more. If you power supply has a voltage spike on start up what does that do to the math.
Yea I understand that. But when I say I have a constant power supply I mean it is a regulated power supply. It is this RadioShack.com

and of course I didn't dismiss his advice. I need to get it tested because I'm having a driver custom designed by my cousin who does that kind of thing on a regular basis but we live a country apart and he isn't doing it overnight :P I'm definitely not rushing though. I was actually convinced it was a pretty damn safe way to test it but still wanted to make sure so I came to ask.

I know the unit won't spike but my cousin did tell me to ask about clean/dirty power and said that might have something to do with it.

---

I also need to remember I'm colorblind when decoding resistors. I lost 2 cheap red ones I got from a wholesale store around here (I practiced using the resistors and the formula to get this power supply to work on a few of those but I definitely gotta have the wife decode the colors for me).

I ASSURE you that no advice goes in one ear and out the other here. This is the most exciting thing I've done to date on a personal project and letting it happen when it happens just makes it that much more relaxing for me. It's also a great benefit to me to listen to years of experience. So for the record... until I get an okay from an experienced member that my supply resistor and setting is safe to use I am holding off :P But if it turns out to be an okay way to do a short test, I would like to do it.

Lucian

04-30-2012, 03:56 AM #11
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Math isn't correct
You are using the correct formula, but you are forgetting that some of the voltage is dropped on the diode and the rest on the resistor, it isn't all on the resistor.

Try:
(supply voltage-Vf diode)/resistance=current

But you shouldn't test it like that anyways. Sometimes I test diodes like that, but using a high value resistor. I would never run a diode so hard with just a resistor because like dtr said a spike in voltage would kill it easily. If you really wanted to test it you should use something higher like 50-100 ohms just so you can see that it works, but this would be at your own risk. Consider any warranty you may have had void by trying that, if you kill it it's your fault!

04-30-2012, 04:01 AM #12
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by Polonium210 I have purchased from DTR before and he has never sent me a dead diode Don't be impatient, wait for your driver.
Why does everyone assume I'm so impatient? Oh wait don't answer that, I've read a lot of new user threads as well.

But hey guys I'm not one of those, please actually read what I'm saying. I'm not saying no one reads it actually I think I'm not conveying my intentions with enough clarity for full comprehension of my motives. But I believe that my last post clarified it so I hope I can get an answer based on that. Thanks all for the thread.

Lucian

P.s. DTR I'd really like to thank you for letting me explain what I meant before getting upset. That is definitely an attitude I respect. Instead of flying off the handle we got to clarify ourselves respectfully. Thank you.

04-30-2012, 04:01 AM #13
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Sounds like a good plan.

Quote:
 Originally Posted by Lucian P.s. DTR I'd really like to thank you for letting me explain what I meant before getting upset. That is definitely an attitude I respect. Instead of flying off the handle we got to clarify ourselves respectfully. Thank you.
I am not the type to get upset.

Have you thought about just picking up a driver that has been widely used and deemed safe for laser diodes instead of waiting on a DIY driver. You can get a driver for around \$15.

You could use a simple linear for the 445

Mohgasm 1.8A linear driver circuit [MOH1.8] - \$14.99 : Cajunlasers Store

And a ben boost for the 405.

http://laserpointerforums.com/f39/pr...cdn-73411.html

Last edited by DTR; 04-30-2012 at 04:04 AM.

04-30-2012, 04:04 AM #14
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by benmwv Math isn't correct You are using the correct formula, but you are forgetting that some of the voltage is dropped on the diode and the rest on the resistor, it isn't all on the resistor. Try: (supply voltage-Vf diode)/resistance=current But you shouldn't test it like that anyways. Sometimes I test diodes like that, but using a high value resistor. I would never run a diode so hard with just a resistor because like dtr said a spike in voltage would kill it easily. If you really wanted to test it you should use something higher like 50-100 ohms just so you can see that it works, but this would be at your own risk. Consider any warranty you may have had void by trying that, if you kill it it's your fault!
Thanks Ben! And yea I'm still not going to do it like I said. But would you be able to explain what the Vf diode part of that equation is?

04-30-2012, 04:09 AM #15
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Lucian
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Quote:
 Originally Posted by DTR Sounds like a good plan. I am not the type to get upset. Have you thought about just picking up a driver that has been widely used and deemed safe for laser diodes instead of waiting on a DIY driver. You can get a driver for around \$15. You could use a simple linear for the 445 Mohgasm 1.8A linear driver circuit [MOH1.8] - \$14.99 : Cajunlasers Store And a ben boost for the 405. http://laserpointerforums.com/f39/pr...cdn-73411.html
Yea I considered it. I actually had a Mohgasm 1.8A linear in my shopping cart and fell asleep (Didn't think to get it from someone else <.<), the next day he changed to the going out of business and I didn't want to buy them in bulk lol. And yea I've been shopping around for a few drivers but as I only understand enough about them to not understand them I've been trying to learn some more before I make my decision.

What I'm actually trying to find is a buck/boost driver like the ben boost but I want the ability to do it off of 2 Li-Ions instead of 1. I also prefer the voltage protection too so I downloaded the R11 chip but can't open the file. Was considering buying the program since I'd like to learn more as I go anyways.

Last edited by Lucian; 04-30-2012 at 04:10 AM.

04-30-2012, 04:10 AM #16
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Re: Alright got a 12x 405 and a M140 445... let's not blow them.

Lucian;

You can use the 24 ohm resistor to power it up.

The current will be less than 500ma,

because as Ben mentioned, the voltage will be 12-5 or 7 VDC/24 ohms.

That would be ~ 291 ma.

Just make sure all the connections are secure when you turn it on.

LarryDFW
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