Charger's mobile for my LD

Hello,
I wanted to know if a portable charger could light my diode laser in complete safety. Is a DDM sufficient to check the output current of charger to see if it is constant and does not exceed 1.2Amax and 5Vmax of my LD (Obviously I will take a charger whose current suits me).
My diode: NICHIA NDB7412T
Her datasheet: http://redlum.xohp.pagesperso-orange.fr/electronics/data/NDB7412.pdf
Thanks.

You should add driver for electricity peaks, directly connected is not safe at all

Thank you for your response.
Another question share: does the driver 1.25A SL-D1 of survivallaser supports Invertion polarity? because I accidentally installed the batteries with the polarity reversed and pushed the on/off button for a few seconds.

ahmedmangas said:

Thank you for your response.
Another question share: does the driver 1.25A SL-D1 of survivallaser supports Invertion polarity? because I accidentally installed the batteries with the polarity reversed and pushed the on/off button for a few seconds.

Click to expand...

Sort of but not quite, it will only take a few seconds, then it should burn out the driver but not the diode. This is also true of a few other drivers.

Alan

reverse polarity can damages the driver circuit ? Do I need a test load to be on ?
Thanks.

ahmedmangas said:

reverse polarity can damages the driver circuit ? Do I need a test load to be on ?
Thanks.

Click to expand...

Yes reverse polarity can damage the driver. You only need a test load (and a DMM) if you want to test how much current the driver is set for, or if you have an adjustable driver and want to set the current, or if you need to test a driver to see if it's working. If you're going to build a few lasers a test load is a good thing to have if you need to troubleshoot a problem.

Alan

Directly powering a laser diode from a charger is not a really good idea. It might work well if the charger limits current to a level safe for the diode. You will probably need to drive the diode well below its maximum limits to achieve this though, wasting qutie a bit of potential power.

Also, a multimeter is not reallty the tool of choice to see what is actually going on here. You would really need to connect the charger to a dummy load and look at what happens on a scope. You could have short peaks of currents when plugging it in that you'd never see on a multimeter, even though they can be powerful enough to nuke a diode.

This is not really a fault when it is intended as a charger - things connected to those would be perfectly fine with a brief overshoot of output voltage and current.

If you insist on doing this at least get some protection for the diode such as lasorb or MOV protection limiting over-voltage conditions, as well as some resistance in the line to make that work effectively.

Switchmode 'chargers' and similar power supplies can do really really strange things upon power-up, which has to do with the feedback mechanism inside them. Also they usually have small capacitor between mains and output to reduce interference, but that could set the full mains voltage between the laser diode and its case albeit it very limited current. This will not usually give you a shock if you touch it, but may exceed the breakdown voltage between pins and case on the diode.

Thanks you for your complete reply !
I abandon idea of charger. It was to see if my diode working.
Another question: I connected the driver "1.25A SL-D1 survivallaser" with 1 "UltraFire 3.7V 3000mAh 18650" batteries and the light intensity of the LD "445nm diode 1W" is very low, lower than my red laser pointer 5mW.
Would it not a problem batteries? because the voltage minimum driver input is 4.5V. Now I connect with 3.7V 18650 <4.2Vmin Maybe it decreases the light intensity of the LD? what do you think ?
I will test with two 18650 batteries and I'll see if the LD emits 1 W.

I'm not familiar with that driver, but if it is a buck design (i.e. made to have a lower output voltage than input voltage) that would explain the problem.

Given the minimum input voltage is 4.5 volts i would reckon this IS a buck driver and designed to run a laser diode off 2 or more lithium cells in series. You will probably get good results powering it from 2 cells in series.

Mucking about like this may not be the best way to go about things though: it may be worth getting a current-limited 'bench' power supply. These are available on ebay for $60 shipped or so for a 20V, 3A model. Units at this price point are not all that good, but they are often good enough to test laser diodes and such especialy when you ramp up the current limiting slowly after power on.