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Thread: DIY PAR meter, Yeah you heard me Reply to Thread
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Topic Review (Newest First)
Yesterday 03:24 PM
Quizcat That's what I figured too...You wouldn't probably need to use it very often, maybe once every four to six months to make sure everything is still on PAR, and if not, time to buy new bulb(s).

Where I can see using it more frequently at first is in designing a fixture for a tank. I've been working on several fixtures over the last several months, some good, some not so good. Without a PAR meter it has all been guess work. You know, little algae blooms here or there, some plants not responding like you had hoped, etc... I'll still have to guess at it when building another fixture, but the PAR meter will sure help in determining if I'm on the right track.


Quote:
Originally Posted by mistergreen View Post
A 9V battery will last you years. You won't be using the meter all that much. At first, you'll be measuring everything but then it'll go in the drawer
Yesterday 01:37 PM
mistergreen A 9V battery will last you years. You won't be using the meter all that much. At first, you'll be measuring everything but then it'll go in the drawer
Yesterday 12:30 AM
Quizcat Great idea engineering that kind of voltage latitude into the design. It's nice to know we can use a power supply (ie: brick) to power the CEP if we want to, and not be particularly concerned about burning it up.

Just curious, do you have any estimate of how long the CEP will last on 9v battery power?

Quote:
Originally Posted by O2surplus View Post
Quizcat-

Don't worry about burning up your CEP due to over-voltage. The regulator that it uses is good for 30V/1amp. I use that regulator all the time in applications where it's fed with 24V, and I've never had a failure. The Reg has built in protection circuits that will prevent it from being damaged, so feel free to feed it with any voltage between 7 & 24V.
I had an idea for a wand...but haven't built it yet. I was thinking of using a 1/2" piece of PVC pipe, in whatever length is convenient for the tank in question, then installing some bends using 45 or 90 degree PVC fittings on the end, then feeding the cable through the pipe so that the sensor is pointed up. Conceptually, I was thinking that there may even be a way of permenently connecting the jar, via the cable connector, to a PVC fitting opening at the end of the wand, to give it more rigidity and permanence, but I haven't checked at the hardward store to see what kind of fittings might be available for that part of it. That cable bushing is about 1/2" diameter after all, and it might be adaptable to fit right into a PVC fitting opening at the end of the wand, oriented the sensor at a right angle to the light source...possibly using an adhesive or caulk of some kind to permanently join the cable bushing to the end of the PVC. That would make the entire thing water proof too, versus the metal coat hanger idea. My only reservation is the height off of the substrate that a PVC wand might require, could be several inches, which would require you to allow for several inches of descrepency in relation to not being at the substrate when reading the PAR meter.

Quote:
Originally Posted by rottison View Post
I can get pics tomorrow but just think of the glass tube being the same size as your pointer finger with the photodiode siting on top.
05-20-2015 11:05 PM
mistergreen
Quote:
Originally Posted by rottison View Post
I can get pics tomorrow but just think of the glass tube being the same size as your pointer finger with the photodiode siting on top.
And it's long? I'd worry it would break.
05-20-2015 09:25 PM
rottison I can get pics tomorrow but just think of the glass tube being the same size as your pointer finger with the photodiode siting on top.
05-20-2015 08:59 PM
mistergreen You'd have to provode pictures. Not sure what you mean.
I have an algae scrapper with a long handle and prongs. I use that to get anything to the bottom of my 75G if I don't feel like getting my arm wet.
05-20-2015 07:55 PM
rottison the glass tube is about half as big again as the photodiode. So there is not a lot of extra room. has anyone put a handle on this? I can't reach the bottom of my tank with out standing on a foot stool
05-20-2015 06:45 PM
mistergreen
Quote:
Originally Posted by rottison View Post
after reading that the shrink wrap didn't work out is due to just not enough surface space at the end for the diode to read from I was planning on putting mine in the bottom of a glass rod about the size of a pencil 12mm with the small piece of white diffuser in front of the diode. does the surface area need to be bigger as in the 1 inch small paint jars ?
Not sure but It definitely needs to be bigger than the photodiode.
05-20-2015 06:00 PM
rottison after reading that the shrink wrap didn't work out is due to just not enough surface space at the end for the diode to read from I was planning on putting mine in the bottom of a glass rod about the size of a pencil 12mm with the small piece of white diffuser in front of the diode. does the surface area need to be bigger as in the 1 inch small paint jars ?
05-20-2015 05:05 PM
O2surplus Quizcat-

Don't worry about burning up your CEP due to over-voltage. The regulator that it uses is good for 30V/1amp. I use that regulator all the time in applications where it's fed with 24V, and I've never had a failure. The Reg has built in protection circuits that will prevent it from being damaged, so feel free to feed it with any voltage between 7 & 24V.
05-20-2015 03:41 PM
mattinmd
Quote:
Originally Posted by Quizcat View Post
I was mostly concerned about the PCB circuitry, and how it was designed, whether introducing too much current might burn it up.
Yeah, you don't have to worry about introducing too much current into the board as long as your voltage is right.

Your US wall sockets can deliver 15-20 amps (varies with how your house is wired), but your 60w desk lamp only runs at 1/2 and amp because that's all it will allow at 120v.
05-20-2015 03:21 PM
Quizcat I was mostly concerned about the PCB circuitry, and how it was designed, whether introducing too much current might burn it up.

[quote=mattinmd;7878785]As for burning up, which part were you concerned about burning up? The power brick or the CEP?

Yeah, the thread is so long, and the design effort took such a long period of time, around 4 years I think, that it's hard to keep track of how things progressed. But, the Arduino design is still just as viable an option. It's just that the PCBs are a smaller footprint. For me, it was just more concise with respect to getting a working CEP. I had some of the PCBs made in Asia based on 02Surplus' PCB design, which is posted somewhere within the thread, around a third of the way through the thread I think. If you go to the very first post in the thread, it may be there too. I still have a few of the PCBs left. You would have to obtain the parts and solder them to the PCB, get the LCD and plug it in, etc...If your interested in a clean PCB send me a PM.

Quote:
Originally Posted by mattinmd View Post
I was digging through the thread and it looked like early stuff was using an Arduino, but that's obviously changed...
05-20-2015 02:19 PM
mattinmd
Quote:
Well, I'm not sure how this compares to the Arduino. This is the version that's the stand-alone PCB/LCD designed by 02Surplus, similiar to the Arduino I suppose, but I don't have the technical expertise to know whether in the process of making this a stand alone PCB, Arduino-less, there was a circuit change that would effect the power supply aspect
Fair enough...

I was digging through the thread and it looked like early stuff was using an Arduino, but that's obviously changed... Regardless, is there a schematic around for the o2 surplus board? I couldn't find one. Being battery powered it almost certainly has a regulator because batteries don't have stable output voltage..

Quote:
But, you're right, the current draw has got to be really small compared to most bricks out there. That was my concern, burning it up.
As for burning up, which part were you concerned about burning up? The power brick or the CEP?

With the low current draw the brick should be fine.

It is also safe to use a brick rated for higher current draw with your device... Power bricks are constant voltage devices. Thus, a 9v, 1 amp power brick will provide 9v, but won't force 1 amp into your device (it would have to raise the voltage to do that). The current rating on a power brick is just an upper limit before the power brick will fail in some fashion.

Constant current power supplies exist, but are inherently variable voltage. They also tend to have issues if there's nothing connected to them as a load, thus they aren't really usable as power bricks. Can you picture how well people would react to a power brick that self destructed if you accidentally disconnected it from the device it was powering while it was still plugged in to the wall?
05-20-2015 02:15 PM
mistergreen The onboard regulator is there for a 9v.
05-20-2015 02:01 PM
Quizcat Well, I'm not sure how this compares to the Arduino. This is the version that's the stand-alone PCB/LCD designed by 02Surplus, similiar to the Arduino I suppose, but I don't have the technical expertise to know whether in the process of making this a stand alone PCB, Arduino-less, there was a circuit change that would effect the power supply aspects. But, you're right, the current draw has got to be really small compared to most bricks out there. That was my concern, that I could potentially burn it up if I exceeded the current capacity of the PCB using a power supply instead of a 9v battery, not to mention the heat factor.

Quote:
Originally Posted by mattinmd View Post
You could always measure the current draw, but given that you are able to run off a 9v battery your current draw is likely very low, at least compared to what even the smallest power bricks can handle..

You're probably under 20ma, and even the smallest power bricks can deal with 100ma.

Also, assuming you're using the correct power input to the arduino (the power jack, instead of feeding 5v pin directly), you should be able to get away with a pretty wide range of voltages too... There's a regulator on the arduino to bring it all down to 5v, although the higher the input, the hotter the regulator will run. Regardless you're probably safe from 7v to 12v.

If you were feeding the 5v pin directly, you'd probably have blown your board with the 9v battery already.
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