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PLTB450B puts out only a flash

alessnilsen

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I managed to get it to work with the LPC-815, first I turned it on with the LD connected set to 400mA, then I measured the voltage across the LD, I got 3V. Next step was to set the voltage trimpot to 3V.

Using the osciloscope I seen that when the TTL goes high, it aplies whatever voltage was set on the voltage regulator, then, it starts regulating the current, so the solution was to limit the output voltage to the max voltage the LD takes at 400mA, so when the TTL goes high, it aplies 3V, that is safe, I got it running and tested. So I let this as a advertisement.
 

Cyparagon

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when the TTL goes high, it aplies 3V, that is safe,
Wrong. That means it is being driven in constant voltage mode. You may get lucky a few times, then pop it a few days down the road. The forward voltage drop of a diode varies with temperature and current. 3V does NOT mean 400mA across it.
 

alessnilsen

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So, what kind of damage can occur? If the diode starts draining more current, then the voltage will be reduced by the current regulator.
 

Cyparagon

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You said so yourself there is a lag before the current regulation kicks in. That's been my finding on these types of boards as well. I've seen delays as long as half a second. It only takes microseconds for damage to occur.
 
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alessnilsen

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Yeah, that's true, I don't recommend this board, I still using it because is powering a LPC-815 and I have 5 more of it in cause that one gets damaged.
 

boraicho

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Good day.
I have this same problem. When connect to power source, so after short time brightness of laser diode are decrease.
i send video
i use LM317 as CC or also i try to connect straight to source via resistor. But in both cases is same behavior.
 

diachi

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What's your input voltage? What current is the LM317 set at? Is it heatsinked? What is your multi-meter showing? Is your resistor sized appropriately for the amount of power dissipated? Need more details.
 

boraicho

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thanks for interest. I am did first tried with LM317 with solid setted output current. But then what you can see on video, is only voltage supply and one 5W resistor in series and i'm did set voltage until was 0,9A on output.. i hope that you understood me.
I have a lot of skills with electronics , but 1W blue laser diode i am tried first time. I tried also purple 405nm 120mW laser diode, but there was not any problem.
 

Anthony P

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I had a similar problem once. It turned out to be that the input source current before the driver was too low. Turned up current on bench supply and everything was fine.
 




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