Poor boy Diode/Driver Testing Lab

[AaronT]

I tried a few searches but haven't found a thread on this.

Thanks to the introduction of the Hyperion LPM I'm wanting to put together a budget/hobby diode testing lab.

Obviously measuring output is covered by the LPM.

Is there an inexpensive way to measure the "nm" of the beam accurately with home built equipment? Cost for various accuracy?

Is there an adjustable pot driver that would be appropriate to use to power a wide variety of diodes being tested?

I see a few options for evaluating the Drivers. Is there an established "best cheap" way to test the drivers?

Thanks guys. If I have good success building/assembling this lab I intend to offer at least a step by step, if not, offer the lab as a kit.

 

[Benm]

For the wavelength ('nm') you have several options. There is no easy to buy device you point a laser into that has a display that will display '532' with a green laser.

One thing you can build quite easily is a set-up with a grating and a target. You measure the angle the laser beam is deflected by the grating and calculate its wavelength. If you don't know the exact pitch of the grating you will have to make calibration points with known sources. This is obviously very low cost and can be quite accurate if you build it properly and calibrate it or get a grating with tight specs.

A bit more expensive would be to get a spectrometer you connect to a computer. These are typically used to measure the spectrum of lamps and such, but with a ND filter can also measure laser wavelength. Accuracy is a bit variable, 1 nm off usually doesn't matter for these things. You can work out a correction factor if you have a known wavelength laser.

One big upside here is the availability of cheap references: DPSS lasers have very exactly define wavelengths, and even the cheapest 532 nm laser will give you a reference accurate down to the nanometer.

 

[AaronT]

For the wavelength ('nm') you have several options. There is no easy to buy device you point a laser into that has a display that will display '532' with a green laser.

One thing you can build quite easily is a set-up with a grating and a target. You measure the angle the laser beam is deflected by the grating and calculate its wavelength. If you don't know the exact pitch of the grating you will have to make calibration points with known sources. This is obviously very low cost and can be quite accurate if you build it properly and calibrate it or get a grating with tight specs.

A bit more expensive would be to get a spectrometer you connect to a computer. These are typically used to measure the spectrum of lamps and such, but with a ND filter can also measure laser wavelength. Accuracy is a bit variable, 1 nm off usually doesn't matter for these things. You can work out a correction factor if you have a known wavelength laser.

One big upside here is the availability of cheap references: DPSS lasers have very exactly define wavelengths, and even the cheapest 532 nm laser will give you a reference accurate down to the nanometer.

How accurately could you determine nm using beam deflection?

Assuming say a 20 ft (or less) work space?

Where could I source the grating with a known pitch?

 

[Cyparagon]

Most gratings will have a pitch listed. Your accuracy will vary, but I wouldn't bet on much better than +/- 5nm unless you've really got dimensions locked down.

Proper driver testing requires a test load (<$10 in parts), various heat sinks if necessary, a good bench power supply ($100-500), and a digital storage oscilloscope ($300+). There is no "poor boy" variation for this.

 

[AaronT]

Knowing the nm and wattage of any given laser for a $200 budget sounds good.

For real testing I guess you would have to be willing to fry $20 $100 and up diodes from time to time. At that point your beyond hobby.

 

[paul1598419]

I have a sheet of diffraction grating of 1000 lines per mm. The sheet is about 20 cm X 60 cm and at one meter is accurate to +/- about 1 or 2 nm. I used to cut it into one inch squares. I no longer use it, though. You'll need a good heat sink to put diode modules into and a good variable power supply that you can adjust the voltage and current with. Nothing compares to a good spectrometer, though, and they don't come cheap. Even after you get the spectrometer you will need to calibrate it and buy the software to run it on your computer. The software alone costs over $200.00. I ended up having to get another laptop as my USB2000 won't work properly on Windows 8 or above.

 

[Cyparagon]

Knowing the nm and wattage of any given laser

The words you're looking for are wavelength and power. You don't ask someone "what kg and metres are you?" for example.

 

[AaronT]

The words you're looking for are wavelength and power. You don't ask someone "what kg and metres are you?" for example.

Unit of measure often dictates equipment needed to make the measurement.

I want to know mW and nm, there for I asked how to measure them.

 

[Cyparagon]

Do you want to know your pounds and your inches too? Or do you want to know your weight and height?

 

[Trendkilla254]

The words you're looking for are wavelength and power. You don't ask someone "what kg and metres are you?" for example.

That's because we live in 'merica. We measure in feet and inches here.

(I'm sorry I really just couldn't resist)

 

[AaronT]

Thoughts/Opinions of this power supply?

3 Digits LED 0 30V 10A Mini Adjustable DC Power Supply US Plug 110V 60Hz E0M7 | eBay

 

[Benm]

That link doesn't seem to work from here, but when searching for it get a lot of those cheap generic power supplies with adjustable current and voltage. I would not use those to directly drive laser diodes really, as they can have overshoots on power-up etc.

They are okay to power proper laser drivers -from- though, where you don't rely on the power supplies current limiting to save the day.

As for the wavelength you could probably get it right to the nanometer with a grating and 1 meter long target, if you have something to calibrate the setup like a dpss laser.


As far has people using the imperial units go: why do you talk about laser wavelengths in SI units like nanometers when you have perfectly good alternatives like nano-yards or mirco-inches? Something like a pico-furlong would seem excellent to get usable numbers for visible wavelengths as well.

The only practical thing imperial here would be the shipping time, which is between 1 and 3 forthnights typically from china

 

[AaronT]

That link doesn't seem to work from here, but when searching for it get a lot of those cheap generic power supplies with adjustable current and voltage. I would not use those to directly drive laser diodes really, as they can have overshoots on power-up etc.

They are okay to power proper laser drivers -from- though, where you don't rely on the power supplies current limiting to save the day.

As for the wavelength you could probably get it right to the nanometer with a grating and 1 meter long target, if you have something to calibrate the setup like a dpss laser.


As far has people using the imperial units go: why do you talk about laser wavelengths in SI units like nanometers when you have perfectly good alternatives like nano-yards or mirco-inches? Something like a pico-furlong would seem excellent to get usable numbers for visible wavelengths as well.

The only practical thing imperial here would be the shipping time, which is between 1 and 3 forthnights typically from china

I can't seem to find grating in relation to measuring wavelength. Do you have a link?

 

[Benm]

I can't really find a good part for sale, but even this stuff should work (with low power lasers):

Diffraction Grating Roll Sheet Linear 1000 Lines mm Laser Holographic Spectrum | eBay

I remember having glass gratings back in school. Currenly i can only find what looks like plastic ones, for example:
Educational Diffraction Grating - Buy Physics Instruments,Educational Experiments Product on Alibaba.com

I guess you can find something good with a bit more effort searching.

 

[AaronT]

Hobby laser power and spectra testing for less than $150.

Is this what I'm looking for?

https://www.amazon.com/Angle-Diffraction-Gratings-Coated-Lighting/dp/B00VWLS3NC/ref=sr_1_2?ie=UTF8&qid=1474158734&sr=8-2&keywords=glass++Diffraction+Grating

 

[Benm]

Post back if you find any.

I remember we had quite a bunch of optical components in diafilm slide sized holders, including gratings, polarizers and monochromatic filters. Sadly i have no idea where those came from, but i think they were pretty old even back then. Perhaps produced in the 70s or 80s - not totally sure.