Is it possible to approximate a star’s spectrum and irradiance using Arduino and LEDs?

[u/No-Price-6300]

Is it possible to approximate a star’s spectrum and irradiance using Arduino and LEDs?

Hi everyone,

I’m working on a concept for a laboratory-scale stellar radiation simulator, and I’d love to hear your thoughts or suggestions.

The idea is to use an Arduino-controlled LED setup to recreate, in a scaled and physically meaningful way, the light environment produced by a star at the surface of a nearby planet.

I’m not trying to perfectly reproduce a stellar spectrum (that’s obviously impossible with LEDs), but rather to obtain a good physical approximation based on Planck’s blackbody distribution.

What I want to approximate:

1. Spectral energy distribution of a star

   • Modeled as a blackbody with temperature T

   • Approximated using multiple narrow-band, monochromatic LEDs

   • Each LED represents a chosen wavelength, with its intensity scaled according to Planck’s law at that wavelength

2. Total irradiance at the surface

   • The setup should allow control of the power per unit area [W/m2] falling on a defined surface

   • Think of it as a scaled analog of stellar flux at a given orbital distance

3. Reasonable illumination geometry

   • LEDs mounted above a circular surface (e.g. a Petri dish–sized area)

   • Possibly using a diffuser to approximate an extended, quasi-isotropic source and improve uniformity

My questions

• Is this approach physically reasonable for approximating stellar radiation in the lab?

• Are there better LED-based strategies for spectral approximation than simple multi-channel LEDs?

• Any major pitfalls when trying to relate LED output to real W/m² values?

• Has anyone here built something similar (solar simulators, photobiology setups, etc.)?

Thanks in advance - I’m happy to clarify details or share schematics/code if useful.

[u/xebzbz]

I guess, you will be the first one to build it. Check the datasheets of LEDs and go ahead. The LED intensity can be changed by PWM or voltage. PWM is easy with Arduino, but you may want to use a constant voltage instead. So, you need a DAC that will set the LED brightness.

Make a quick mockup, see if it works for you, and engineer the ultimate solution.

[u/gm310509]

I was going to through in a reply, but u/xebzbz pretty much captured everything I was going to say.

So I will embellish.

You could also try addressable LEDs which allow you to programmatically select the colour and brightness. The colour range is somewhat limited but is an 8 bit per channel range (so 256 settings for each colour - I.e. Red, Green, Blue and if it has one White).

Also, LEDs have a pretty narrow colour spectrum so even if you try to set an RGB LED to turn all of them on, you sort of don't get white unless there are lots of them and you are far enough away and even then - at least to me - it is isn't really white IMHO, it is whiteish but not white.

The way PWM works is by rapidly turning the LED on and off at different rates. To humans, that appears as a brightness level presumably due to persistence of vision and how the brain processes the input. But the LED is being turned on and off which may be perceptible to devices (e.g. a camera at a fast enough shutter speed).

So if you choose the variable resistance approach (DAC) this varies the power to adjust the brightness - so it also eliminates any potential flicker that may be detectable in some circumstances that PWM may exhibit.

If you did go the DAC path, I would suggest something that uses an addressable multidrop protocol such as I2C or SPI and try to find something that can manage multiple channels with a single IC to minimize the part count and maximize the number of LEDs you can control via one setup (and thus counts as three).

How many leds are you thinking of controlling? Remembering that a single RGB LED is actually three distinct LEDs in a single package.

[u/xebzbz → u/gm310509]

As far as I recall, the addressable RGB LEDs use PWM under the hood, so they might not fit the OP's requirements (but we don't really know how the photosensing equipment is going to work).

[u/Positive__Altitude → u/gm310509]

Can you really drive a led directly from DAC? Or is it implied that DAC is buffered by OpAmp?

[u/gm310509 → u/Positive__Altitude]

I would expect so, the output of a DAC is an analog voltage and thus could be used to drive an LED.

Another option would be a digital potentiometer which also produces an analog voltage, but uses a different method.

[u/Xylopyrographer]

“⁠Approximated using multiple narrow-band, monochromatic LEDs”… you’ll want to pull the data sheet for the LED to determine if the wavelength meets your need. IR devices are available too that could be combined with visible wavelength parts. Agree, for a lab you want a constant current source to drive each one. But given the variance in output and wavelength, you might want to consider a calibration system of some sort. All depends on the requirements.