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ArcticMyst Security by Avery

LPC-815 250mw Red Laser

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May 20, 2010
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Hello, i'd like to know if I use a LPC-815 diode with a FlexDriver with 2x 1.5v AA battery, with 400mA will work fine? Thanks
 





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Mar 17, 2010
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It should work fine. I have a LOC running on almost 500mA and it works fine. Though you'll need a heatsink, because at these currents the diode and the driver heat up really fast.
 
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I just tested mine set @ 420 mA with a flexdrive and it outputs 250-255 mW :)
and 420 mA is a safe current if you use your lasers <30 seconds each time
 

Kevlar

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I just tested mine set @ 420 mA with a flexdrive and it outputs 250-255 mW :)
and 420 mA is a safe current if you use your lasers <30 seconds each time

Ditto, this is what I run mine at [except I use a rckstr driver and 7.2V (2XCR123s)]but as has been said, a heat sink and duty cycle are a must if you want it to last :beer:
 

Kevlar

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Ditto means the same. I.e. I run mine at 420mA and it outputs 250mW - 255mW. The only difference in my setup is were I noted, that I use a rckstr driver.
 
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I use a homemade DDL driver and a glass lens. The current is around 470mA and the power output 245-255mW.
 

atobe

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what kind of source voltages are you using to get so high ? I just turn my lpc815 into a led. :( i was using 4 AA rechargeable batteries. i had it set @ 200mA. since that's the max my multimeter measures to.. so i went to turn up the pot a lil bit and it leded... oh yeah i'm using the rckstr driver thanks.
 

Morgan

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Hey atobe,

You are going to need around 5V to make it work properly so the batteries you had should technically have been fine but were they fully charged and/or working correctly. What voltage do they say on the side?

How did you set your current? Did you use a Dummy Test Load?

Is your diode properly installed in a module and/or heatsink?

Is your driver healthy with all contacts and components secure?

The RCKSTR is a linear driver that needs about 2.5V above that of the diode you are trying to drive. For the LOC, (Long Open Can diode from the LPC-815 sled), that means somwhere around 2.5 to 3V. plus your 2.5V for the driver gives you about 5V. I think if you go to the, 'Pro Shop', section there is a stickie about the RCKSTR that gives required voltage above diode voltage and if you go to the, "Diode Compilation", thread the details for that diode are in there.

Below the required voltage the driver falls out of proper regulation so the first thing to do after visually checking the driver, connections and components, is get a confirmed power source for your setup and reset the output current using a Test Load. If your batteries are weak or suspect then your diode might not be LEDed, just under lasing threshold. It is possible it has suffered permanent damage but I personally have not seen that from dropping out of regulation, (others may have though). Each diode is different so yours may not have taken kindly to the unregulated current. It is also possible that the diode was damaged in some way during extraction or installation but, as I said, the first thing to do is check your connections, driver and components then power it correctly, check your current and then see.

I'm sure I'll have missed something obvious out so other voices will join in as necessary...

Hope you find the problem.

M
:)
 

atobe

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yes the diode was in the axaiz module.. i mean it worked for a while i played with it for may be 1 hr.. total on time may be 10 mins tops. with each time being on was no longer than 30 seconds...

batteries are fully charged again 5.16V is what it reads
i didn't use a load test diode or resistor since RCKSTR's manual said the best way was just to take the LD leads from the driver and measure the mA with a mutlimeter which was what i did.. it's exact reading right now is at 198.2mA. you are right about the needed voltage i measured it at the diode end and it gives out 4.69V with out the diode attached.. but when the LD attached it reads 2.47V ..

i ordered another diode same one again just to see.. thanks for any other inputs this is my first build :)

i just tested it again this time with a 7.2V source same results ..except the ending voltage w/o diode is 6.47V but still 2.47V with diode attached.. i think it's dead .. i should of just left it alone @ 200mA
 

Morgan

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A couple of points now then...

When you measured voltage without the diode in circuit you measured the volts that your DMM, 'wanted'. When you measured the volts with the diode in circuit you measured what the diode, 'wanted'. That's how these linear drivers work, they supply the correct voltage that is required to maintain a selected current so as you turn the input voltage up, your DMM will measure higher as it then, 'wants', more, but your diode will still only require 2.47V. (I think that's the correct description... )

How were you measuring mA again? In series with the diode or in parallel? It actually sounds like you just hooked up you meter to the LD outputs as if it were your diode, correct? This is not the right way to do it and will not set the driver. If we go back to what the driver needs to properly regulate the current, (~2.5V), then you were putting in 5.16V and getting 4.69V at the outputs. The driver couldn't hope to regulate with only 0.47V. The driver would not have been in correct regulation and you could have been putting way too much current to the diode. I suggest what the RCKSTR manual was actually trying to tell you was to connect the meter in series with the LD output leads and measure the current as a flow through the diode. Another, and perhaps safer way, (for the diode as it minimises disconnection risks), is to again measure current in series but at the input to the driver. The input current is the same as the output current.

The problem you had is an excellent example of why we set current with a Test Load. It nails the current before ever risking a diode. When replacing the Test Load with a diode it must be remembered to short the driver outputs to discharge the capacitor or you can give your LD a spike it will never forgive you for!

Also bear in mind that some drivers, (namely Dr.Lava's), do not respond well to being powered with no load. And when I say do not respond well, I mean they die! These MUST be set with a Test Load and only ever powered after that with an LD in place.

I suspect you have damaged your diode but now that you have, you can check current in the correct way just to show yourself, (and us), that you have more than 200mA going through it, although your meter doesn't read any higher than 200mA does it. Hmmm. A new meter should now be on your tools list I think. ;)

I hope that's more help and you get up and running soon. Dare I mention goggles? Sounds like you are after quite high powers and you should be using them already...

M
:)
 
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atobe

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yes it was measure in series with the diode it's still reading 198.2mA .. i'll see again once i get the new diode.. i'm not really after high power i just wanted it to light a match or pop ballons but so far it hasn't done that .. guess i have to make a tester diode then

thanks for all the help morgan
 

Morgan

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Ok, that is the right way to get a current measurement, (try doing the same at the driver input end. It should give the same results and is perhaps a better practice). 200mA should be enough to get a match to light, (somewhere around 150mW I think). Maybe a darker colour match next time?

A Dummy Test Load just gives piece of mind and you will come to rely on it later anyway so now is a good time to make, (or buy), one. I can't remember if I mentioned Flaminpyro builds really nice ones. You will be able to eliminate other possible faults before risking your new diode too.

No probs for the help. That's why we're all here... To build lasers and help other people build lasers! :wave:

If anyone can add to this thread then please jump in.

M
:)
 




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