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Lpc826 not bright help

Shiraiei

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The LM317 + resistor in current limit mode is a driver... Which should work, providing you use a test load to check it before hooking up the diode. Always keep ESD in mind too, diodes are very sensitive to static shocks.
Alright thanks for the suggestion ,hope my next try would succeed
 



thanhtung

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do you think that 500mA is too high with your lpc836?
- my experience , you should set current at 370- 410mA with lm317 + 3.3ohm ~~> 250-300mW
 

Alaskan

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I have heard the same from others, to run those diodes more conservatively or they die too easy. Also, I'm not sure he had the diode properly heat sinked yet.
 
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GSS

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I have heard the same from others, to run those diodes more conservatively or they die too easy. Also, I'm not sure he had the diode properly heat sinked yet.
You mean running it before it was in to what looked like a Axis brass module?
 

Alaskan

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Yea, or perhaps it just went over current and LED'd, maybe something else went wrong.
 

icecruncher

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Given the price of the diodes and that he is new to here and using a resistor. I immediately thought LED. You can buy a tray of these for less than $3 each last time I bought them.

But for a cheap laser to play and practice and learn with, that is a great choice IMHO. Still has enough umph to burn but not too pricey and would impress anyone who isn't really into lasers much with what it can do.
 

Alaskan

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I’d order the LPC-840, one listing on ebay is under 9 dollars.
 

hakzaw1

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If you do everything the same next time..... well you know..(don't be shocked by the same outcome).. thought in yr OP you wrote that you bought 2 pcs ..no?
Find one of the good tutorials and skip NO steps.
good luck
 

Cyparagon

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While the circuit is ACTIVE, please measure the following: voltage across the battery, voltage across the laser diode, and voltage across the resistor.
 

Shiraiei

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Alright update so I made a new laser driver which is lm317t current limit.mode with a 3.9ohms resistor but when I try it with a 12 volt power supply with a test load,I can't seem to measure the current across the 1 ohm resistor on the dummy load, would be thankful if someone could help thanks
 

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Immo1282

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This is probably not your issue - but it would definitely help if you got a modern multimeter - It seems that you're pretty new to putting circuits together, so having to factor in the loading of a moving-coil voltmeter into your measurements may not be helping you so much...

On to your circuit - can you draw a diagram of what you've got? It's reasonably difficult to pick out what you're doing from your picture - but I'm pretty sure you've wired it up wrong The circuit should be like the diagram below. Note well that the pinout of the LM317 does not match the drawn pinout arrangement on the schematic diagram.

63794

Another thing - when you get it working, I'd want to rebuild your circuit on a prototyping PCB before you connect it to a diode - Laser diodes may not tolerate the harsh transient changes that an insecure connection will cause - Good solid soldered joints are really the easiest reliable connection to make here.
 

Shiraiei

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This is probably not your issue - but it would definitely help if you got a modern multimeter - It seems that you're pretty new to putting circuits together, so having to factor in the loading of a moving-coil voltmeter into your measurements may not be helping you so much...

On to your circuit - can you draw a diagram of what you've got? It's reasonably difficult to pick out what you're doing from your picture - but I'm pretty sure you've wired it up wrong The circuit should be like the diagram below. Note well that the pinout of the LM317 does not match the drawn pinout arrangement on the schematic diagram.

View attachment 63794

Another thing - when you get it working, I'd want to rebuild your circuit on a prototyping PCB before you connect it to a diode - Laser diodes may not tolerate the harsh transient changes that an insecure connection will cause - Good solid soldered joints are really the easiest reliable connection to make here.
I actually finally got my laser diode to work and it's so bright ,I made this work by using the a lm317t ,capacitor,diode and a 3.9ohms resistor all connected in a breadboard.but once I switch to the driver as in the picture and used a 9volt to connect to the diode ,it lights up properly,but it did not last long before turning into a weak laser pointer. What I can think went wrong is probably the driver being shorted because I did not wire it nicely.
 
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Immo1282

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Please don't connect your driver to any more laser diodes before you can properly verify with a meter and test-load that it's working correctly. It's a massive waste of your money if you do this and killing laser diodes is a totally avoidable situation if you've taken the right steps.

It's possible you were overdriving the diode - as they can go "LED" on you, it's also possible that the diode was damaged by heat - as your module is really too small to soak up much heat from a powerful diode for more than a few seconds at a time.

Please slow down - killing LDs is not fun :)
 

Shiraiei

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I'm basically just hooking up the laser diode to a driver similar to the picture but with no pot and resistor changed to 3.9 ohms.i don't think I can measure the current correctly because my multimeter seems to just go as high as 0.25 mA.

For the calculation of the driver, I take 1.25 divided by 3.9 which gives me around 320mA and according to the lcp826 graph it's only around 200mw.
Please tell me if this is correct,thank you
 

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Immo1282

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Oh hang on a second - You can't measure the current on your multimeter in the current mode with a Shunt resistor! You should measure the voltage drop across that shunt resistor and use I=V/R to calculate the current. This is why 1ohm shunts are ideal - as that way I=V*1 so you needn't calculate anything.

Set your multimeter to a DC Voltage range instead, measuring the voltage across the resistor. Better yet, put your analog moving-coil meter on a museum shelf and get a cheap digital DMM as it'll save you a lot of headache in the long run.
 

Shiraiei

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Oh hang on a second - You can't measure current on your multimeter in the current mode with a Shunt resistor! You measure the voltage drop across that shunt resistor and use I=V/R to calculate the current.

Set your multimeter to a DC Voltage range instead, measuring the voltage across the resistor.
Oh is that so, I'll definitely try it and see
And what's the difference between a shunt resistor and a normal one?

I'll try to give updates as soon as I can
 




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