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Test load for 445nm

HIMNL9

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650mA must not cause problems to your diodes (apart that they become very hot, if used for long time)

The problem using these diodes is, mainly, the power dissipation ..... for a dropout of 700mV (typical, it increase a bit with more current), you have to dissipate in heat the power adsorbed from the diode chip at a certain current ..... at 650mA, the dropout is a bit more than 700mV, so the power to dissipate is around 0,5W ..... this is inside the safety parameters of the 1N serie diodes, but, with a so small case and leads, the heat transfer rate must be kept in consideration, too .....

Dissipating half watt of power from a case smaller than a normal 1/4W resistor is a thing that can be done safely, for brief times, so if you use the load for set the current, then disconnect it, the only consequence is that the load become a bit too hot, but nothing other ..... if you instead need to use it for long time tests (for test a driver, as example), the heat, accumulating, can also end damaging your diodes, in the long time (heat dissipation is not just a fact of surface, it depend from thermal resistance junction/case, thermal resistance case/air, position, airflow, and some other parameters)

Only for this reason i usually suggest to use overdimensioned components, for long time tests ..... for a quick "set and go" test, those diodes are ok, too
 
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Eudaimonium

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&%=mA must not cause problems to your diodes (apart that they become very hot, if used for long time)

The problem using these diodes is, mainly, the power dissipation ..... for a dropout of 700mA (typical, it increase a bit with more current), you have to dissipate in heat the power adsorbed from the diode chip at a certain current ..... at 650mA, the dropout is a bit more than 700mV, so the power to dissipate is around 0,5W ..... this is inside the safety parameters of the 1N serie diodes, but, with a so small case and leads, the heat transfer rate must be kept in consideration, too .....

Dissipating half watt of power from a case smaler than a normal 1/4W resistor is a thing that can be done safely, for brief times, so if you use the load for set the current, then disconnect it, the only consequence is that the load become a bit too hot, but nothing other ..... if you instead need to use it for long time tests (for test a driver, as example), the heat, accumulating, can also end damaging your diodes, in the long time (heat dissipation is not just a fact of surface, it depend from thermal resistance junction/case, thermal resistance case/air, position, airflow, and some other parameters)

Only for this reason i usually suggest to use overdimensioned components, for long time tests ..... for a quick "set and go" test, those diodes are ok, too
700mV, not mA , I believe. Please correct that to avoid confusion :D

And yeah, you have a point there.

How many unknowns came up with these new diodes... unbelivable.
 

Flaminpyro

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I will soon have some PYRO supper duty dummy loads avable for all
they will have a 3 amp rating ;)
 

FireMyLaser

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1 ohm may be too high resistance for 1A and up, it makes a 1V drop pat 1A which is pretty significant. 0.1 ohm may be a lot better.
 
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HIMNL9

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You're right, 0,1 ohm is much better in this case ..... only, this way you have a 10mA resolution, instead 1mA (except if you have a multimeter that can read 0,1mA) ..... but, thinking about that, who really need an 1mA resolution, trimming a driver for 1A ? ..... :p :D
 

Eudaimonium

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You're right, 0,1 ohm is much better in this case ..... only, this way you have a 10mA resolution, instead 1mA (except if you have a multimeter that can read 0,1mA) ..... but, thinking about that, who really need an 1mA resolution, trimming a driver for 1A ? ..... :p :D
Good point!

Well, after all, we are talking about trimming drivers like microboost, but the apsolute maximum rating is 1A, so basically just maxing out the driver is OK with damned 445nm amper-eater.

On the other hand, when I make drivers I have a habit of avoiding potenciometers whenever possible, I just use fixed resistor, no need for test load at all.

But other than these two exeptions, new era of laser contructing has begun.
 




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