Reef Discussion

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
Any Interest in a DIY Light Meter
Whilst trawling a few sites over the past week or so I came across this digital luminosity/lux/light meter which can be used with an Arduino microcomputer.
awww.adafruit.com_images_medium_tsl2561quarter_MED.jpg



The TSL2561 luminosity sensor is an advanced digital light sensor, ideal for use in a wide range of light situations. Compared to low cost CdS cells, this sensor is more precise, allowing for exact lux calculations and can be configured for different gain/timing ranges to detect light ranges from up to 0.1 - 40,000+ Lux on the fly. The best part of this sensor is that it contains both infrared and full spectrum diodes! That means you can separately measure infrared, full-spectrum or human-visible light. Most sensors can only detect one or the other, which does not accurately represent what human eyes see (since we cannot perceive the IR light that is detected by most photo diodes)
Whilst I am not suggesting for a second that this would be a replacement for a high quality lux meter, I think that it would be more than adequate for our purposes. I have often wished that I could measure the differences between different led combinations, current levels etc and I am fairly confident that this would meet my requirements.

I have ordered one and should have it in a week or two.

I then started thinking that maybe other members may also be interested if the price was right. Whilst it can be hooked up to an existing Arduino, it needs to operate over the i2c bus at a 3.3v logic level compared to the default of 5v so this may prevent other things on this bus operating correctly. So, it would probably be easier to use a stand alone Arduino.

With a bit of searching I have been able to find these components (approximate prices only):

Light Meter $12.50
Arduino $15.80
9v Battery Clip $3.00

There are a few variables which can be changed so some type of input device would be preferable.

Basic LCD Keypad Shield $7.50 - it would be difficult to install this in a case, but could be done.

The cost of touchscreen TFT LCD's has reduced considerably and we could get a 2.2" Touchscreen and shield for about $25.00

Case, connectors, wire etc - not sure but should be about $10.00

To encase the sensor, and make it waterproof I have been looking at small acrylic boxes which are used for displaying gemstones - these are around $1.

So, all up, around $40 for the basic lcd, without case OR around $70 for the touchscreen LCD fully enclosed.

A Real Time Clock could be added for around $10 - this might be useful to time stamp recordings that could be saved in memory.

I can do the programming at no cost and will put everything together.

As you may not require the use of one all the time, maybe a few members want to get together and buy one as a group??

As mentioned, the prices noted above are approximate only and I may be able to get things cheaper once I start getting serious.

So, would anyone be interested in something like this?

Expressions of Interest received from:

Synodontis and/or K&J Aquatics
rockerpeller
DavidS
 

Rob

Member
Apr 26, 2012
743
424
Interested for sure. Have been looking at this unit which is submersible to connect up to my RaspberryPi tank monitor.....
http://atlas-scientific.com/product_pages/sensors/env-rgb.html

Check out the doco especially special code M2/M3 which provides outputs for RGB,Lux and UV

Was concerned about maximum lx range from 0- 3,235 lux.. As I have no idea how this equates to what we are looking for in par. If it would be suitable it looks great splitting the out into RGB outputs as well. even show a lux value for UV spectrum

The Atlas Scientific ENV-RGB’s strongest
capabilities are found in its ability to read total lux and the
lux of each color individually (R,G,B). This is followed by its
ability to detect red, green and blue light and convert that
light into R,G,B color data. The highest sensitivity for R,G,B
is found at 640nm, 524nm and 470nm wave lengths, respectively.
The RGB data that is output is in true 8-bit RGB
format where each color has a value from 0-255
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
What sort of time frame you looking at MagicJ
Just as a follow-up to this - given the small numbers I will finance this until the units are completed.

The basic code is already available but the touch screen code is going to take me a while to get my head around so I wouldn't think this will be completed in less than 2 months.
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
Interested for sure. Have been looking at this unit which is submersible to connect up to my RaspberryPi tank monitor.....
http://atlas-scientific.com/product_pages/sensors/env-rgb.html

Check out the doco especially special code M2/M3 which provides outputs for RGB,Lux and UV

Was concerned about maximum lx range from 0- 3,235 lux.. As I have no idea how this equates to what we are looking for in par. If it would be suitable it looks great splitting the out into RGB outputs as well. even show a lux value for UV spectrum
Looks like an interesting unit and is no doubt of a higher quality than the one I am getting, but it is also over 3 times the price.

My idea with this was to keep the price as low as possible whilst still obtaining a usable product.

This chart gives you an idea of lux values (obtained from http://en.wikipedia.org/wiki/Lux)

Examples
Illuminance Surfaces illuminated by:
10−4 lux Total starlight, overcast sky[3]
0.002 lux Moonless clear night sky with airglow[3]
0.01 lux Quarter moon
0.27 lux Full moon on a clear night[3][4]
1 lux Full moon overhead at tropical latitudes[5]
3.4 lux Dark limit of civil twilight under a clear sky[6]
50 lux Family living room lights (Australia, 1998)[7]
80 lux Office building lights in hallway/toilet[8][9]
100 lux Very dark overcast day[3]
320–500 lux Office lighting[10][11][12]
400 lux Sunrise or sunset on a clear day.
1,000 lux Overcast day;[3] typical TV studio lighting
10,000–25,000 lux Full daylight (not direct sun)[3]
32,000–130,000 lux Direct sunlight

So, 3,235 lux is a lot less than full daylight.
 

DavidS

The Resident Loony
Jul 17, 2011
3,337
1,033
Ballarat, Victoria
Just as a follow-up to this - given the small numbers I will finance this until the units are completed.

The basic code is already available but the touch screen code is going to take me a while to get my head around so I wouldn't think this will be completed in less than 2 months.
That kind of time frame works for me (current tank money all going into the LFS crawl). Might as well go the touchscreen option :)
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
I will update the first post with prospective takers.

BTW I won't be buying anything until I receive mine and make sure it works.