Questions about first laser build

ApexProxy said:

That will not work unless the driver is under a real load. You need to power something equivalent to your diode for you to test the real current it is driving.

One of these is designed to do exactly that:
3 amp selectable test load [3AMPLD] - $19.99 : Cajunlasers Store

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That is going to be way too expensive. There is fees for importing anything above $14. So this would cost me $19.99 + $5 VAT + $28.1 = 53.09 dollars. That seems too expensive for me xP.

I asked the seller (aixiz) what current they are set on as standard, but i'm still waiting for reply. I could be lucky that they are turned to about what i would like

Else i can turn the pot up until it doesn't get any brighter (This board goes to 500mA) and then turn it a little down to hit about ~ 400 mA.

You can make your own test load very easily and cheap.
Just solder together 4 four 1N4001 diodes (or 1N400x such as 1N4003 etc.) and 1 Ohm resistor in series. (Six diodes are used when building a blu-ray laser)

You should be able to find these parts easily at a local electronics shop. You could make the test load nice by soldering everything on a circuit board with test leads and switchable between red and blu-ray. Or, you can just solder the lead of one diode to the next, to the next, to the next and to the resistor.

Just search the forum for something like DIY test load.

It will be a whole lot cheaper and easier to just throw together a quick test load with a couple dollars worth of parts than it will be to buy a new diode when you kill it. Plus, don't you think it'd be nice to actually know for sure what current your diode is running at?

If you just go and hook everything up and turn the pot and hope for the best you will be surprised at how drastically the current can change with the smallest movement of the pot and just how easily a LPC-826 will pop.

I don't see how importing something costs more than the item itself. Also, just ask clif to label the customs tag as like $6 in goods and you won't have any issues. Or you could make one yourself. Either way is a far better idea than just hoping for the best. Those diodes are anything but robust.

ApexProxy said:

If you just go and hook everything up and turn the pot and hope for the best you will be surprised at how drastically the current can change with the smallest movement of the pot and just how easily a LPC-826 will pop.

I don't see how importing something costs more than the item itself. Also, just ask clif to label the customs tag as like $6 in goods and you won't have any issues. Or you could make one yourself. Either way is a far better idea than just hoping for the best. Those diodes are anything but robust.

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In my contry there is a fee for importing items without paying the 25% VAT of the item (And that is $28.1). And the reason why i don't pay it is because you need to have a company to do it :wtf:

They are pretty strict about importing items. If they believe the package is over the allowed amount they will mail me to send them the receipt on the items. (Damn u Denmark !:yabbmad

I just asked Aixiz what their driver's current is as standard and they replied back with 200mA. I just asked them again how much a 1/4 turn on the pot will cange the current, and i'm still waiting for the answer

If they don't know i will see if i can make that test load board (meaby i can even go to school and make it and use their components (One free load board for me ))

I just got all my questions answered by Aixiz (Great service). Now i'm ready to receive the items and start to build. :yh:

Adjustable Current Laser Diode Driver 80 500mA w TTL | eBay

This driver starts at 200mA and for every ¼ i turn it increases it with 20% (which in this case is 100mA). So for getting 400mA i will need to turn the pot ½ around.

This means i don't need a test load. I recommend getting this driver if you, like me, need a cheap driver and don't wan't to spend money on a test load board.

Thanks for the help everyone.

That method is taking a chance. Its common that drivers are not all exactly the same and that potentiometers are not exactly perfect. Its very unlikely that you will get an exact 400mA but at least you have a little headroom for error at that current. Hopefully it works out but it is not something I would recommend for anyone trying to make more than just one laser. If you plan on this being a hobby of yours then a test load is a must hands down.

Just got the diode today

I took a picture of it and went into paint - is this right?

Yes, that is the correct pinout. These diodes are case negative so they will pull negative from whatever they are pressed in so you need to make sure you know if you can let it do that or if you will need to isolate it from getting power through its module and heatsink or not. The data sheet for the driver should give you some insight into if you will need to or not.

Also, keep note that since its case negative, if you wire negative to it and the flashlight is case positive(you have the + end of the battery touching the rear cap), you will have to isolate the diode from getting power from anything but the wires you solder to it.