DIY par meter
- Thread starter Jrod381
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There are 1/2 doz answers to your question..
Basically a "PAR" (Quantum meter) is just a photodiode and filters.
When building one the hardest thing would be calibrating it.
Need to match it to a known "real" meter..
Second hardest thing is getting a blue enhanced photodiode since most are very weak on the blue end as to response..
Sadly the research really went into the "lux" photodiode curve shape.
Better..see curves.
Actually I 'm lazy tonight and could write a fairly large chapter on this but instead I'll just give you links of some finished ones or some not so finished but concept ones:
Easiest is just modifying a cheap Lux meter.
What diode inside and if it is indeed filtered is a crapshoot I suspect:
Next more err "scientific":
www.plantedtank.net
www.plantedtank.net
www.plantedtank.net
meter pdf
Somewhere there is another paper out there w/ a simple sensor design written decades ago.
Sadly I can't find it. No matter the sensor they used is obsolete.
Bottom line it's just a photodiode, some filters (high/low cutoff filter not needed for LED's, some color filters to equalize sensitivity) w, diffuser (best AFAICT is PTFE) maybe some software trickery and an amplifier/meter and calibration.. oh and a waterproof housing..
Personally got a small tin full of glass shards (filter pieces) and NOS photo diodes I picked up on a whim.
Just never got around to "actualizing" all of it. Besides, at the time, I'd have needed to buy a par meter to calibrate it.
They weren't common nor relatively cheap at the time and the "cheap" ones had some issues for me.. like the drastic cutoff at like 650nm..
Consider this just a whole bunch of useable or not info..
Basically a "PAR" (Quantum meter) is just a photodiode and filters.
When building one the hardest thing would be calibrating it.
Need to match it to a known "real" meter..
Second hardest thing is getting a blue enhanced photodiode since most are very weak on the blue end as to response..
Sadly the research really went into the "lux" photodiode curve shape.
Better..see curves.
Actually I 'm lazy tonight and could write a fairly large chapter on this but instead I'll just give you links of some finished ones or some not so finished but concept ones:
Easiest is just modifying a cheap Lux meter.
What diode inside and if it is indeed filtered is a crapshoot I suspect:
DIY Par Meter, $30-$45
In the spirit of all this DIY cob stuff I apparently fell into, I became curious what else I could do. Google to the rescue. I found this gem of a post on another forum (non growing forum) by a poster named Hoppy. Take a gander and let me know what you think. I ordered the lux meter and...
www.rollitup.org
Next more err "scientific":
DIY PAR Meter
Assembling a DIY PAR Meter
DIY PAR Meter - 2015 Version
Somewhere there is another paper out there w/ a simple sensor design written decades ago.
Sadly I can't find it. No matter the sensor they used is obsolete.
Bottom line it's just a photodiode, some filters (high/low cutoff filter not needed for LED's, some color filters to equalize sensitivity) w, diffuser (best AFAICT is PTFE) maybe some software trickery and an amplifier/meter and calibration.. oh and a waterproof housing..
Personally got a small tin full of glass shards (filter pieces) and NOS photo diodes I picked up on a whim.
Just never got around to "actualizing" all of it. Besides, at the time, I'd have needed to buy a par meter to calibrate it.
They weren't common nor relatively cheap at the time and the "cheap" ones had some issues for me.. like the drastic cutoff at like 650nm..
Consider this just a whole bunch of useable or not info..
You know.. building one yourself has ONE big advantage (w/ the right photodiode).
Current "PAR" meters by definition shouldn't measure anything below 400nm.
Apogee does make an extended version but lets leave that out for a minute..
This sensor dips it's toes in the UV range though suspect sensitivity is a bit low.
https://www.electronicsurplus.com/e...aJzTConn8ZqMf0wCr_BKvaQMFQWQ-A0waAtr4EALw_wcB
330-720nm...
Probably wouldn't need a filter pack.. just calibration in the visual range and count the added response as a bonus.
Certainly not scientific but I believe it's adequate.
I may have one in that can of of mine..
Of course I'm ignoring some of the "teeny" bits like cosine correction and refractive index type things..
That's sort of where the PTFE "cap" would come in
You know.. I may need to dig into that can a bit..now that I have a Seneye as a reference source.. SEE..needed to buy one anyways.
Numbers are Roscolux filters
Add filters if you like..
ATM can't find the RAW sensor response curve.
Doh, right under my note. Pretty sure I don't have one of these. Wasn't what I would have been looking for.
Personally a better one to work with but would need to add an IR cut filter..
Oh just in case you thought I was b s-ing you..
MY (embarrasing) prototype using a photodiode w/ response like above, a blue filter from a microscope stage, the B&W IR/UV cut filter (best short of a Baader)(to keep in the range of 400-700nm (important at the time..) all inside a rubber wall plug housing.
Not shown is a parallel resistor and VOM..
All I can say is it measured something..
Oh yea.. ther is a cork holding the photodiode in..
Current "PAR" meters by definition shouldn't measure anything below 400nm.
Apogee does make an extended version but lets leave that out for a minute..
This sensor dips it's toes in the UV range though suspect sensitivity is a bit low.
https://www.electronicsurplus.com/e...aJzTConn8ZqMf0wCr_BKvaQMFQWQ-A0waAtr4EALw_wcB
330-720nm...
Probably wouldn't need a filter pack.. just calibration in the visual range and count the added response as a bonus.
Certainly not scientific but I believe it's adequate.
I may have one in that can of of mine..
Of course I'm ignoring some of the "teeny" bits like cosine correction and refractive index type things..
That's sort of where the PTFE "cap" would come in
You know.. I may need to dig into that can a bit..now that I have a Seneye as a reference source.. SEE..needed to buy one anyways.
Numbers are Roscolux filters
Add filters if you like..
ATM can't find the RAW sensor response curve.
Doh, right under my note. Pretty sure I don't have one of these. Wasn't what I would have been looking for.
Personally a better one to work with but would need to add an IR cut filter..
Oh just in case you thought I was b s-ing you..
MY (embarrasing) prototype using a photodiode w/ response like above, a blue filter from a microscope stage, the B&W IR/UV cut filter (best short of a Baader)(to keep in the range of 400-700nm (important at the time..) all inside a rubber wall plug housing.
Not shown is a parallel resistor and VOM..
All I can say is it measured something..
Oh yea.. ther is a cork holding the photodiode in..
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Jrod381
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Thanks for all of the info it is greatly appreciated but I think I needed to word my questioning correctly. Basically what I was talking about was just b using an apogee par sensor and connecting that to say a multimeter or laptop.
I have an apogee connected to a multimeter, the handheld monitor from apogee is a total waste of money IMO. A multimeter is far cheaper. Probe + multimeter ran me $175 total I believe for a fully functional PAR meter.
I compared it with a full apogee system at one point and it gave essentially identical readings.
I compared it with a full apogee system at one point and it gave essentially identical readings.
blasterman
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You don't need red sensitivity at all. Just a blue filter that dives below 400nm.
Nobody runs their reef tank with anything more than a couple percent orange or red spectrum at most, so unless you plan on doubling duty for growing dope you just need to measure 400-500mm light.
Nobody runs their reef tank with anything more than a couple percent orange or red spectrum at most, so unless you plan on doubling duty for growing dope you just need to measure 400-500mm light.
chipmunkofdoom2
Always Making Something
Thanks for the info. Do you have any details on this?
Newest Apogee outputs in the microamp range. Needs a good "preamp" so to speak .
blueAcro - Apogee SQ500 Interfaces
blueacro.com
Different versions have different outputs.
Philly Reefer
Valuable Member
Hey all, I am new in this hobby so I do have my own question with this par meter/reading.
How often do you check them? It sound like you check them often enough to justify making/buying them.
I was thinking or renting a par meter from BRS. Did the reading and return them.
Just a one time thing as long I dont change my lights.
Am I wrong?
How often do you check them? It sound like you check them often enough to justify making/buying them.
I was thinking or renting a par meter from BRS. Did the reading and return them.
Just a one time thing as long I dont change my lights.
Am I wrong?
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Jrod381
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which apogee probe did you purchase?
I was looking at the 120 model
The -120 model has a high enough voltage output that its readable on most multi-meters, just multiply by 5. Or use any off the shelf op-amp to set 5x gain.
The -500 models are the higher impedance small signal types. Just all down to the filters and photodiodes. Use a 100x gain with a low noise high impedance op-amp here, and offset the zero point so you can read zero. Note the -500 has a large cosine error when in water (10%). Their "corrected" sensors just add 10%, so feel free to set a 110x gain
The hardest part of the sensor is basically characterizing it. The needed reference light sources and integration spheres are a pretty specialist item - you can always look at renting time from someone to do it. Once you know the response, I doubt there is any line level calibration, and a go/no go test is probably pretty simple with a control sensor and a reference light source.
I’m new, so apologies if this question already posed: is is a refractive PAR sensor, i.e., refractive eg spherical glass optic, with baffles at the right angles to pick off 400-700nm? And then maybe a black body thermal detection, so it is broadband/uniform response 400-700?
I guess aligning it properly to the PAR source, eg lights or the Sun will be an error source. ( this would be more for outdoor application).
and of course I can’t find this idea anywhere on the web, which makes me think i‘m missing something obvious.
thx for consideration,
JP
I guess aligning it properly to the PAR source, eg lights or the Sun will be an error source. ( this would be more for outdoor application).
and of course I can’t find this idea anywhere on the web, which makes me think i‘m missing something obvious.
thx for consideration,
JP
