In line current meter (ammeter) for LED arrays.... geek time! - The Planted Tank Forum
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post #1 of 26 (permalink) Old 02-12-2011, 04:21 AM Thread Starter
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In line current meter (ammeter) for LED arrays.... geek time!

Well, I stumbled across these dudes the other day.

Basically, you wire them in series with your dimmable LED arrays (one per driver).


They will give you an instant current readout. That way you know just how much current you're juicing your array with, at a glance. And, you get lots of geek points for having these really cool digital number thingys on your canopy.

It's not that critical to know your current level, but it's helpful if you ever have to dim your array, and then return it later to the light level you originally had it set to (assuming you don't always run your LEDs at 100%). It's often a bit tricky trying to get light levels back to that "sweet spot".


Here are a few that I checked out. They need a 6-24v DC input (ie, basically something you already have laying around extra that's 6-24v). This is just to light up the backlight and lcd screen.


Note the shipping prices on these. Some are free, some aren't. All come from China that I've found so far.

I think I'm going to try 3 of these dudes.
[Ebay Link Removed] 0-2A Green LCD Digital Ammeter Current AMP Meter - eBay (item 250759083635 end time Feb-16-11 00:25:32 PST)[/url]

[Ebay Link Removed] DC +/- 5A Blue LCD Digital AMP Panel Meter Ammeter - eBay (item 250599164625 end time Mar-12-11 19:58:29 PST)[/url]

[Ebay Link Removed] 5A Blue LCD Digital Ammeter AMP Meter No Need Shunt - eBay (item 170534985921 end time Feb-28-11 07:58:24 PST)[/url]
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post #2 of 26 (permalink) Old 02-12-2011, 04:22 AM Thread Starter
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Well they removed the Ebay link, even though this is the only place I can find these.

Just search Ebay with the descriptions in the post above, you'll find it.


They go from $5 up by the way.
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post #3 of 26 (permalink) Old 02-12-2011, 04:43 AM
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Very Cool

I just ordered two

Thanks
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post #4 of 26 (permalink) Old 02-12-2011, 08:29 PM Thread Starter
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Lol, nice!

Let me know how they work.

I fully plan on ordering some, but I have several other money grubbers to take care of first.

The nice thing is I can always notch the canopy out since I have power tool galore sitting around. I'll have to make this one of my last items to buy since it's a toy more than a necessity
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post #5 of 26 (permalink) Old 03-05-2011, 03:52 AM Thread Starter
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Quote:
Originally Posted by rvcrawford View Post
I just ordered two

Thanks


I just ordered 3 of them. A red display, a green, and a blue. I may only need two of them but these are coming from China, so you never know.


Let me know how they work out.
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post #6 of 26 (permalink) Old 03-18-2011, 10:39 PM Thread Starter
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Mine arrived today which is reasonably quick coming in from China.

They look a touch cheesy and I just noticed that they have a max voltage of 48, which happens to be very close to the voltage I'll be running them at (40-48). Hopefully they will last.
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post #7 of 26 (permalink) Old 03-19-2011, 01:11 AM
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Can't you use a simple two resistor voltage divider to get a lower voltage? I'm getting more interested in these now, because I can see a good reason to calibrate my LED light, for PAR vs Current. Right now I think I have a bit more PAR than I want, so if I had one of these on the light it would be very easy to dial whatever PAR I want. (I have just about talked myself into getting one!) If there were more room inside the Meanwell housing it would be simple to add it there.

Edit: I just bought a 2 amp one to mount on my LED light, which runs 1.3 amp max,, perhaps a bit higher. I knew I shouldn't have started reading this thread.

Hoppy
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post #8 of 26 (permalink) Old 03-19-2011, 01:21 AM
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I got mine a while back. I checked the current draw and at 10V they each draw 50ma. I was able to connect them both to my 10V power supply that feeds the 0-10V signal pots. They work great. I'll post pics later.

Roger
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post #9 of 26 (permalink) Old 03-19-2011, 04:30 AM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
Can't you use a simple two resistor voltage divider to get a lower voltage?
You'll have to edumacate me on this one. I'm only a seed-picker when it comes to electronics. I've always been suspicious of using resistors in the actual LED circuit because I fear that it will cause the Meanwell to do strange things. It somehow senses the necessary voltage for the LEDs and it seems to me that it would either compensate for the resistor I add, and raise the voltage up to where the LEDs need it... or something else odd.



Quote:
Edit: I just bought a 2 amp one to mount on my LED light, which runs 1.3 amp max,, perhaps a bit higher. I knew I shouldn't have started reading this thread.
I've said that about a number of things, many times. I think you are 100% right on their usage. If you take some PAR readings at 1,000mA, 700mA, 500mA, and so on.... then you have a VERY good idea of where your PAR is if you ever need to adjust it. I will be doing that exact same thing.

Quote:
Originally Posted by rvcrawford View Post
I got mine a while back. I checked the current draw and at 10V they each draw 50ma. I was able to connect them both to my 10V power supply that feeds the 0-10V signal pots. They work great. I'll post pics later.

Roger
I plan on doing the same thing with my canopy. I will have 3 Meanwells and will run the 9v supply I use to dim them to these panel meters. Very convenient. The only hard part about setting this up is figuring out how I want to mount them on my canopy. The clips on them are designed to be attached to a VERY thin plastic panel, and my canopy is 3/4" birch plywood. I will have to fabricate something--- maybe brushed aluminum--- and notch it out to accept the panels. In fact.... I think the local Lowe's sells some 1/16" aluminum sheet stock in 5X7 or similar pieces.... .
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post #10 of 26 (permalink) Old 03-19-2011, 02:46 PM
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I like having the meters because I know if I set the blue to 200ma and the white to 800ma, the color will look good and the heatsink will run right at 105 degrees all day long.

I used a thin piece of mahogany to mount the meters inside of the cabinet.

Roger




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post #11 of 26 (permalink) Old 03-19-2011, 05:04 PM
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This is how I see hooking the ammeter into the LED circuit. Does anyone know if this will work?

Hoppy
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post #12 of 26 (permalink) Old 03-19-2011, 09:41 PM Thread Starter
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Well, mine work . I tested them today. They are consistent down to about 0.00 amps, but they vary by about 0.005 (5 mA) which is completely inconsequential for our purposes.


SCHWING!

I am slowly becoming the quintessential redneck geek, if such a thing exists.
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post #13 of 26 (permalink) Old 03-19-2011, 09:52 PM
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Quote:
Originally Posted by redfishsc View Post
Well, mine work . I tested them today. They are consistent down to about 0.00 amps, but they vary by about 0.005 (5 mA) which is completely inconsequential for our purposes.


SCHWING!

I am slowly becoming the quintessential redneck geek, if such a thing exists.
How are you powering the ammeter?

It has occurred to me that a single resistor in series with the power lead to the ammeter will drop the voltage down to whatever we want to power it at, between 6 and 24 volts. So, for 99 cents at RadioShack you can get 5 - 680 ohm, 1/2 watt resistors. Connecting two of them in series, then 3 of them in series, then putting those two series resistors in parallel, you drop 48 volts down to about 7 volts. So that should work fine, at little cost. The trouble with using a single resistor is the power rating of the resistor has to be high, and the value would be a non-standard value.

Hoppy
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post #14 of 26 (permalink) Old 03-20-2011, 12:29 AM Thread Starter
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I tested them using a 9v battery. Spliced them inline on my LED array temporarily. I just used the shunt from the first one, unplugged it, and plugged it into the others to test them. I DEFINITELY powered off the Meanwells when I swapped ammeters since it's a very, very bad idea to break the circuit with the Meanwell in operation. Good way to blow the LEDs.

Since I'll have several Meanwells using a 9v dimmer circuit (and they only draw 50mA) then I can sprout off the + lead of the 9v and run all three ammeters from the same 9v supply. Mine are rated at 750 or 850mA so I'm still well within spec.
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post #15 of 26 (permalink) Old 03-20-2011, 12:34 AM Thread Starter
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As a side note, we have an unusual facility at the Seminary I attend called the "Sharing Shop" which is basically a second-hand store, where students and local citizens donate useful stuff for Seminary students to get for free.

They have an ENORMOUS stash of power supplies, all the way from cell phone chargers to laptop chargers. I was in there the other day and they had a 220v to 120v stepdown transformer lol (like, a commercial equipment component type, not a fancy plug-n-play type).

So I get every 9v supply they have when I see them. I test them just to make sure but normally they are pretty good .
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