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ArcticMyst Security by Avery

help identifying diode and specs






AUS

AUS

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First make sure you have adequate eye protection for this, a watt at IR is very nasty. You can get reflections off lots of objects and you can't see the beam being IR.

If you google 1000mW 808nm data sheet you would be wanting about 1.4amps to drive this. A simple linear driver would probably be better as you will only need about 2.2volts foward current. Note you will need a BIG heatsink for continuous operation.

I note it says "Between 800 and 900nm" so they could be anything but are probably 808nm at that price.

What are you planning on doing with it?
 
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cyclonite

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I just want to add this to my collection of laser builds, not intending to use it on a daily basis etc.

So now I need to know the diode's internal resistance so that I can calibrate a constant current driver. How do I find this out? The seller sent me a .PDF which says it should be driven at between 1.2A - 1.6A so you're spot on. It also says to drive it at 2.0V - 2.2V.

Could you please recommend a driver that's suitable for this?

Thanks again.
 
AUS

AUS

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Is it to be in a hand held or a "lab" style mount?

You don't have to work out the internal resistance and use a resistor, but this changes with temperature. Safer to build a current regulator that will feed it the right current no matter what the voltage.

You have lots of choices, you could go for a linear driver or a buck driver. I'd probably go for a tried and true LM317 based linear driver as its simple and easy to get bits for. They are a bit big for a handheld but you'll need lots of heatsinking on that diode anyway.

If you search the forums and google for "LM317 constant current circuit" you should find something. You will need about 3.5 volts to drive it with (to overcome the voltage drop in the regulator). You could also search for "buck" drivers in the forums although most f these are lower current than you need.
 
AUS

AUS

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Our posts crossed...
Yes the LM358 is a good linear driver and I have bought from Odic before they are a reputable company. You will need to heatsink the big chip on the driver though, use heat sink compound and bond it to something big and metal..
 
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cyclonite

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Ahh that's perfect then.

So let's rehearse this. I'll hook the 3.7v Li-ion battery to the input, discharge the output and then hook it up to the LD via my ampmeter. At this point the driver's pot is turned to minimum. I'll then turn it on and slowly crank the pot up until the amperage reads just over 1A and stop there. Correct? I'd feel much more comfortable setting the current on a dummy load but without knowing the internal resistance I can't do this can I?

btw, it'll be a lab laser, not handheld. I don't have an enclosure for this yet.

Thanks.
 
AUS

AUS

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If you search the forums you can find some dummy load designs, most use a resistor and some diodes (number of diodes depends on the laser forward voltage, for IR you would want two or 3 in series), have a look in the Drivers, Test loads and Power Supplies section of the forum. IR diodes have a similar forward voltage drop to red diodes.

I'd set the current through the load to an amp or so then hook up the laser with an ammeter in series and slowly raise it up.

There are some links here and here.
 
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cyclonite

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Hi Aus,

I've made a silly mistake by assuming the TO-5 9mm diode will fit in an AixiZ module. It turns out I need a larger one and so I purchased this set:



Now how and where should I apple the heat-sink compound? I guess around the back after pressing it in?

Thanks again.
 
AUS

AUS

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Glad to be of help :)

Yes you get diodes in 3.8mm, 5.6mm and 9mm. You can get 9mm AixiZ modules, several members here sell them, I have a 9mm 445nm diode in a copper AixiZ.

The heat sink compound goes around the diode before you press fit it so it fills any holes between the heat sink and the diode, but don't get any on the front window!

Be careful of the duty cycle too, with a 1 watt diode you will find it gets hot fairly quick, you will have to experiment with on/off times to keep it cool enough so you don't fry it.

Make sure the lens you get is designed for the diodes wavelength too, and make sure its glass not acrylic at that power level. If you use a lens with an AR coating for the blue end of the spectrum on infrared it may fry the anti reflective coating or melt the lens.

Where abouts in the world are you by the way? I'm guessing UK?
 
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cyclonite

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Yes UK.

Yes the glass lens comes with the module as a set and this is all for the IR diode that the same seller sells.

So once I've set the linear driver to about 1A with a 3.7V input voltage, what happens if I connect an input battery that has a voltage of about 4.0V? Would that fry the diode? I take it more voltage would go to the diode then and exceed the 2.2V max rating?

Thanks again.

Cheers :)
 
AUS

AUS

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No it should be OK at 4V, IR diodes are similar to red ones and they can handle a fully charged Lithium battery OK.

The voltage is just the pressure pushing the current though the diode and the diode will only suck as much current from the batteries as the driver lets it handle. As long as you don't exceed the maximum VF it should be OK. A data sheet would be nice though.
 
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cyclonite

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hmm but the seller listed the max voltage at 2.2V so I take it that's the max VF? Is that what you're referring to? In that case I can't use an input greater than 3.7V right?
 
AUS

AUS

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Sorry I'm pretty tired, just realized that in constant current mode the regulator will drop the voltage anyway.

I also had a look at a few charts on these forums and looking at a red (LPC-826) laser diode hooked up to a constant current power supply, the voltage increased as the current did from about 2v to about 4v.

I have a green 50mW laser diode module here that's pumped with an IR diode (I'm guessing its about 250mW) and I put it on the power supply and it was fine from about 2.5v to over 4v although the driver started getting hot at just over 4 volts.

So 4V should be fine, but i wouldn't exceed that :)
 
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cyclonite

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ok thanks. Now I've just ordered some 1N4001 and a 2W 1 Ohm resistor. I need to build my own dummy load because the normal ones can't take over 1A. I'm going to use 2 1N4001 in parallel to get them to handle 2A and stack them up like that.

now I'm not sure how that black housing works, and am worried if I'll be able to 'press' the diode in without a vice. hope it won't be too difficult. any tips here?

thx.
 
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