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DIY PAR meter, Yeah you heard me

299K views 740 replies 110 participants last post by  henrybri 
#1 · (Edited)
*Edit 5-10-13
NOTICE - Firmware has been updated for outdoor lighting.

Final product list:

Photodiode: VTB8441BH
price: $4.660
http://www.alliedelec.com/search/productdetail.aspx?SKU=70219652

Cosine diffuser: 1/8" thickness, 2447 white plexiglass
price: varies, get the sample or buy a big sheet of it.
http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Black_and_White
http://www.usplastic.com/catalog/item.aspx?itemid=23681

Basic 16x2 Character LCD - Black on Green 5V
price: $14 but you can get it cheaper on e b a y
http://www.sparkfun.com/products/255

Arduino Uno
price: $30
http://www.sparkfun.com/products/10356
http://www.sparkfun.com/products/11021 (newer model)


Diagram
 
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#59 ·
I took the white plastic off the sensor and measured the light outside the tank.

I noticed measuring in the tank full of water was giving me higher readings that didn't fall on the inverse law curve.

over all cost:
~$10 - photo diode + S&H
~$.50 - plastic paint cup
~$4 - electrical cord
~$30 - ardiuno MP (there's a $20 version too, and there's a $5 texas instrument one)
~$.50 - 27K resistor

total: $45.00
 
#62 · (Edited)
Ok, I built an app to output the 'PAR' data.

Big numbers for us old folks.


And an option to choose which port for it to listen to. You can do a wireless connection if you hook a bluetooth radio to the arduino :)
**Admendment**

If /dev/tty.usbserial-a9007muf is not the first item on the list, choose that... On windows, it might be COM1.

***************
You can download the app on my forum.
http://aquatictechtank.net/viewtopic.php?f=11&t=150&p=390#p390
 
#70 ·
I've thought about it :)

I need to find a way to design the sensor better. It's clumsy with the epoxy, maybe a heyco grip cord is better.
The LCD is a better way too but obviously $14-$15 more expensive. And the microprocessor needs to be designed too. It can't be left exposed where water can get at it :)

Unless, I can just get all the parts, program it and let you guys handle the assembly. That would keep cost down.
 
#75 ·
And I received my LCD and battery holder today and couldn't wait to hook things up.. What else to do on a cold rainy day?



First 'hello world' test run.

And hooking everything up, batteries included.... Sorry for the self promotion there.


The next part is to figure how things will fit together and make all those wires look not so scary.
 
#77 ·
Meter AND sensor (minus ship & handling) looks to be under $50.

Accurate? hmm. tough question... It is by no means as accurate as a PAR meter mainly because of the photodiode used and lack of cosine correction.

There was a chart in past posts where I compared my readings to Hoppy's readings. It came close enough.. I can't really give a +- percentage error. In Hoppy's chart, the curves are margins and not lines. I don't think reading light is an exact thing, correct me if I'm wrong.
 
#78 ·
You don't need an exact reading, and even a PAR meter doesn't give you that. All it takes is slightly tilting the PAR sensor and the reading changes, plus there is an error range for the distance between the sensor and the light to consider also.

Ideally you will borrow a commercial PAR meter and calibrate yours against that, but I can understand that not being easy to do.
 
#81 ·
You don't need an exact reading, and even a PAR meter doesn't give you that. All it takes is slightly tilting the PAR sensor and the reading changes, plus there is an error range for the distance between the sensor and the light to consider also.
Yeah, kind of make sense not to spend $300 on a par sensor & meter then.

yeah, short of getting lucky and finding something that will fit nicely inside the slot that needs to be crimped and using pliers.. you'll most likely have to get a hold of some actual crimpers to make sure it won't pull out on accident.
Yeah, I'm going to The Home Depot later to grab a crimper. Maybe I'll make a few of these to sell to recover the cost of the crimper :)
 
#85 ·
Ok,
Here it is, the unveiling.

It fits comfortably in your hand.


It just made sense to have the sensor detachable and not soldered into the board. I used a telephone jack as the interface.


And the underside.
[

The only thing is I forgot or never bothered to design it with an on/off switch :).... To turn it off, I yank a battery out... I'll have to think about a switch.
 
#87 ·
I added an on/off switch!

But I almost blew up the whole thing :D

I was confused on how to wire up a switch and then the machine started feeling warm/hot. You know you're in it deep when it turns into a heater. Basically, I created short circuit.

Can't wait to try his out tomorrow.
 
#90 ·
Really interesting to see all of the par values in the tank.

substrate area
22 PAR - (under large plants) smaller plants will not grow, they die off actually.
60 PAR - plants grow slowly
180 PAR - (open area) plants will grow but with algae :)

I'm seeing GSA at the top of my crypts where I'm getting 280 PAR. I might get a glass cover for my 75G and see how the PAR will drop. I need something for stopping the fishes from jumping anyway.
 
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