Need Help: Estimating PAR

kentuckyclowns · 11/04/2011, 07:16 AM

There are countless threads out there for DIY LEDs but I am curious to know if anyone could help estimate what my PAR levels would be. I have 36 (3 rows of 12) LEDs, alternating cool white and royal blue, with each string of 12 driven by a meanwell 60-48 dimmable driver. Currently I have 60 degree optics on 26 (the outside leds) and the remaining 10 leds (inside/middle row without the first and last leds) have no optics (120 degree beam angle). The fixture would hang about 12" about the tank which is 18" deep. The tank is a standard 29 gallon (30 x 12 x 18).

I know its a long shot but nobody near me has a par meter to test this system out. I'm hoping to get a rough idea so I know if I can swap my T-5 light out for the LEDs. Thank you for any and all advice!

rtparty · 11/04/2011, 10:19 AM

To be completely honest, there is NO way of estimating PAR. It just isn't possible. There are so many factors that determine PAR that an estimation is not possible. Sure someone could come here and have the same setup and say they are getting 300 PAR 6" under the water surface and then you think you should be close to that.

Then in reality you test and only come up with 150 PAR. Why? Shouldn't they be close? No, they shouldn't be. Flow, rockwork, and many other things contribute to an overall PAR reading.

Let's not even get into the fact that the average PAR meter used in this hobby is under reading LEDs. Some numbers have shown they may be off by more than 40%.

We could even talk about how your optics are creating hot spots in the tank and PAR might be 100 or so and moving the sensor an inch to the right and all of the sudden you are registering 250 PAR. Which reading is correct?

Just too many factors.

TheFishMan65 · 11/04/2011, 10:55 AM

And you didn't even mention LED type or drive current. Sorry, I agree you are out of luck.

However for a 29 gallon 36 should be more than enough to grow just about anything, IMHO.

kentuckyclowns · 11/04/2011, 11:32 AM

That's pretty much what I figured. The meters are just way too expensive for me right now.

As far as conversions are concerned, can you equate footcandles to PAR estimates?

TheFishMan65 · 11/04/2011, 01:13 PM

Probably not since PAR takes in spectrum. Have you considered getting just the PAR sensor for about $150 and hooking it up to a multimeter?

kentuckyclowns · 11/04/2011, 01:37 PM

Yeah..that's out of the question..$150 goes a long way in my budget. My grandfather has a footcandle sensor though..which is why I wanted to know if it would work as a rough estimate.

mike&kel · 11/04/2011, 01:39 PM

Call the company u bought the LEDs from.

---
I am here: http://maps.google.com/maps?ll=36.098962,-119.559294

11/04/2011, 07:16 AM	#1
kentuckyclowns Registered Member Join Date: Jul 2010 Location: Kentucky Posts: 121	Need Help: Estimating PAR There are countless threads out there for DIY LEDs but I am curious to know if anyone could help estimate what my PAR levels would be. I have 36 (3 rows of 12) LEDs, alternating cool white and royal blue, with each string of 12 driven by a meanwell 60-48 dimmable driver. Currently I have 60 degree optics on 26 (the outside leds) and the remaining 10 leds (inside/middle row without the first and last leds) have no optics (120 degree beam angle). The fixture would hang about 12" about the tank which is 18" deep. The tank is a standard 29 gallon (30 x 12 x 18). I know its a long shot but nobody near me has a par meter to test this system out. I'm hoping to get a rough idea so I know if I can swap my T-5 light out for the LEDs. Thank you for any and all advice!

11/04/2011, 10:19 AM	#2
rtparty Raise The Reef! Join Date: Oct 2008 Location: Utah Posts: 7,404	To be completely honest, there is NO way of estimating PAR. It just isn't possible. There are so many factors that determine PAR that an estimation is not possible. Sure someone could come here and have the same setup and say they are getting 300 PAR 6" under the water surface and then you think you should be close to that. Then in reality you test and only come up with 150 PAR. Why? Shouldn't they be close? No, they shouldn't be. Flow, rockwork, and many other things contribute to an overall PAR reading. Let's not even get into the fact that the average PAR meter used in this hobby is under reading LEDs. Some numbers have shown they may be off by more than 40%. We could even talk about how your optics are creating hot spots in the tank and PAR might be 100 or so and moving the sensor an inch to the right and all of the sudden you are registering 250 PAR. Which reading is correct? Just too many factors. __________________ Ryan Click on my user name and check out my homepage! Current Tank Info: 50g Cadlights/Giesemann Spectra (250w Radium, 2 ATI Blue Plus, 2 ATI Actinic)/2 x Vortech MP10wQD/Skimz SN123/Eheim Compact 3000+

11/04/2011, 10:55 AM	#3
TheFishMan65 Registered Member Join Date: Aug 2009 Location: Northern VA Posts: 4,618	And you didn't even mention LED type or drive current. Sorry, I agree you are out of luck. However for a 29 gallon 36 should be more than enough to grow just about anything, IMHO. __________________ Click my home page for Thread Summaries Current Tank Info: 75 gallon lps and fish

11/04/2011, 01:13 PM	#5
TheFishMan65 Registered Member Join Date: Aug 2009 Location: Northern VA Posts: 4,618	Probably not since PAR takes in spectrum. Have you considered getting just the PAR sensor for about $150 and hooking it up to a multimeter? __________________ Click my home page for Thread Summaries Current Tank Info: 75 gallon lps and fish

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11/04/2011, 11:32 AM	#4
kentuckyclowns Registered Member Join Date: Jul 2010 Location: Kentucky Posts: 121	That's pretty much what I figured. The meters are just way too expensive for me right now. As far as conversions are concerned, can you equate footcandles to PAR estimates?

11/04/2011, 01:37 PM	#6
kentuckyclowns Registered Member Join Date: Jul 2010 Location: Kentucky Posts: 121	Yeah..that's out of the question..$150 goes a long way in my budget. My grandfather has a footcandle sensor though..which is why I wanted to know if it would work as a rough estimate.

11/04/2011, 01:39 PM	#7
mike&kel Registered Member Join Date: Jul 2009 Location: fresno, ca Posts: 131	Call the company u bought the LEDs from. --- I am here: http://maps.google.com/maps?ll=36.098962,-119.559294