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# Solar Panel-Driven LPM?

#### Wolfman29

##### Well-known member
Hey guys.

Probably not the first to suggest this, but, to put it bluntly, can't we measure optical power using a solar panel? I believe that light intensity over equal areas of paneling is proportional to voltage output....

I tested this out with three of my lasers. My 532 seems to want to measure around 350mV, my LOC around 420mV, and my 445 around 420mV. Now, there is something wrong here because my blue is about 400% stronger than my LOC. But maybe there are coefficients we can use for calculating optical power for given wavelengths?

Any thoughts?

#### Lotus_Darkrose

##### Well-known member
I'm not sure about measuring, but it would be fun to try with 2 different power outputs of the same wavelength to see if it can be used to roughly compare. I'm going to assume from what my 445 did to a broken cell phone screen, that I wouldn't want to be shining too high power of a laser on a solar panel (and by that I mean it burnt a hole through the screen when I focused it)

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#### Wolfman29

##### Well-known member
As long as you don't focus it, it should be fine But yeah, that's the goal. Anyway, my ~1W 445nm didn't really do much damage, so I think it's alright.

#### piferal

##### New member
Hey guys.

Now, there is something wrong here because my blue is about 400% stronger than my LOC. But maybe there are coefficients we can use for calculating optical power for given wavelengths?

Any thoughts?
It is normal to give you different readings because the photovoltaic cells react differently with each wavelength, making extremely difficult to do what you want.

It would have to perform a complicated series of corrections for each wavelength to calculate the real power.

Or putting forward filters to correct, something too complicated.

Is similar to powermeters made with photodiodes which are also wavelength-dependent, that is why usually requires the user to make a setting when measured for different laser wavelengths

#### lasersbee

##### Well-known member
^^^ that is exactly correct...
Most optical sensitive semiconductor materials (solar cells...
Photo Diodes..etc) have a non linear optical sensitivity curve
that would need to be corrected for any wavelength being
measured.
Different optical sensing materials will also exhibit different
curves.
You are also limited to a low power density because the
sensing material will saturate... get hot and even damage.

You would need Neutral Density filters to use powers over
100mW-200mW (depending on the sensing material).

Here is our 200mW HLPM II. It uses an optical Sensor and we
supply an Optical correction chart for commonly used wavelengths...

HLPM II

Jerry

#### Wolfman29

##### Well-known member
Mm. Interesting.

So I really don't mind, at all, having to do a bit of math to try to figure it out. Math is free, LPMs aren't So does anyone know a place I can find a cheap, decent solar panel with information about it's reactivity to different wavelengths?

The solar panel I have is really old, crappy, and I have no information on it But I wouldn't mind doing some multiplication.

#### Lotus_Darkrose

##### Well-known member
Oh, I was viewing this as just a fun little experiment, lol. Wasn't aware you were trying to do this instead of using an actual lpm.

#### lasersbee

##### Well-known member
Mm. Interesting.

So I really don't mind, at all, having to do a bit of math to try to figure it out. Math is free, LPMs aren't So does anyone know a place I can find a cheap, decent solar panel with information about it's reactivity to different wavelengths?

The solar panel I have is really old, crappy, and I have no information on it But I wouldn't mind doing some multiplication.
Here's one at DigiKey......
They supply a data sheet for the part...

Digi-Key - PDB-C613-2-ND (Manufacturer - PDB-C613-2)

Jerry

#### Wolfman29

##### Well-known member
@Lotus:
Yeah... I am poor

@Lasers:
Thanks! Will look into it.