interesting idea, please help. i'm somewhat a noob

hello everyone, i'm new to this site but not so much new to electronics. i took an electronics class my freshman year (it is my summer between my sophomore and junior year of high school) so i know some of what i need to know (ohms law, resistors, LED's, diodes, etc) but i'll admit it out front there is still a lot to learn, so if i do not know a term or something of the sort on here please don't bash on me. what i thought would be interesting to do is something that as far as i know has never been done before. i wish to start a miniature aquarium in my school locker. now before you jump to crazy conclusions you can relax because i have looked up the handbook and manual and read/re read it countless times and it is not against the rules at my school, so i can do this. also, i'm not really for keeping fish in such small tanks. i know it is done and under proper conditions it is successful, but it won't be done in my tank for multiple reasons. one is because the fish will probably die, and two being that if a teacher asks if i have a "fish" tank in my locker i can openly say no. no, what i plan to keep in my locker is much more interesting than fish... i plan to keep corals. that's right. corals. do not worry i have corals currently in a larger tank and am knowledgeable in their requirements, one(the most obvious) being light. another being flow but some corals do not like flow so that will be asked upon further research as to what i plan to keep in there. filtration will be biological and basically be provided by the rockwork and the sand i put in the tank. basically, all i need is the lighting. "but wait" you might ask," you plan to do this in a locker, and there is no power plug in a locker..." well that is the reason i am posting this incredibly long thread asking for help. the lighting has to be battery powered. that is also what stops me from just buying lighting from online or making it myself.

here are the constraints to the project:

1)the lights must be battery powered. or if anyone knows a way to produce voltage in a small amount of space please let me know.

2)i hope to have 12 royal blue led's on a heatsink and 6 leds cool white or a color similar
-the important ones are the 12 royal blues because that is the light the corals use to grow. 12 on at the same tie is way to much for a tank the size of what i need, so what i plan to do is have 6 on at a time while the other six are off to provide longer batteries

3)i know powering all 18 led's at once using a single battery for 8 hours a day is near impossible, so most likely i'll have to use multiple circuits, preferably one battery powering one or two led's. that way it'll be much easier to have six on and six off at the same time.

4)i have a limited amount of space. the aquarium i intend to use is a 5 gallon and the footprint is 16" by 8" and i plan to build a small canopy to conceal the lighting with the exception of the switches and the batteries on the outside so i can change them easily.

5)the lights will be on for 8 hours each day, from when i come in at 8:00 AM until when i leave which is 3:30 Pm. after that they will be off until the next day, which is why they require a switch to turn on/off and i will change batteries when necessary.

what i am asking for is the circuitry to help me with this. i am fairly new and do not remember everything since my freshman year, though i have been researching quite a bit.

i am off of school until halfway through august, i hope that with the community participating i can have this done by halfway through july to get ready and just install it when the year starts.

please bear with me, i know if enough people pool together what they know and contribute this project can get done. this is as far as i know what i would like to add to the tank. any questions feel free to ask and i'll answer what i can.

We will need some specs on your LEDs. Voltage and current. If the current is very high batteries won't last long. Couldn't you use a power supply like your phone charger instead?

The source I plan to get them from has this information



Emitting Color :Royal Blue
DC Forward Voltage (VF): 3.4 ~ 3.8Vdc
DC Forward Current (IF): 700 mA
Viewing Angle: 120 Degree
Luminous Intensity: 30LM-40LM
Reverse Voltage: 5.0 V
Wave Length: 445-450nm

And for the warm whites

1. Forward Voltage: 3.2-3.8V-700MA 45milx45mil
2. Luminous flux: 180-200LM
3. Output power: 3w
4. Light Color: Warm White 3000-3500K
5. View angle: 120-140
6: LED support：Copper


I can't use a phone charger because there is no outlet in to plug the charger in.
Sorry if this isn't the data you asked, i only worked with LEDs once and that was far below what this is.

What's the battery rating?

Battery 1.5 v. The standard AA battery.

Except rechargable. Unless there is a better one I could be using. I am starting from scratch and have no idea what components I would need except the battery and the lights. I have nothing bought yet, I'm going make a list of everything I need and then get the pieces. That is why I hope to have everything planned out by mid-July.

fishyfish22 said:

Battery 1.5 v. The standard AA battery.

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How many? Alkaline? NiMH?

NiMH is preferable and I would think that there would be 9 each one powering 2 led's (3 for the warm whites 6 for the royal blue)

How would I go about creating a circuit thatwould make this work? What would a schematic look like?

A typical 1.25V NiMA AA is around 2500mAh or 3.125Wh (Watt Hours). Simple math shows your 3W LEDs will work for about an hour per charge, BUT that'll never happen in real life. Conversion to a higher voltage and current limiting such as the LEDs require will reduce that.

Multiply the forward voltage x current to determine the wattage of an LED, e.g. 700mA x 3.6V = 2.52W and that's going to chew through any AA battery pretty fast.

You're going to need to rethink your power source or LED solution, plus your locker is going to glow and I can't imagine it going unnoticed.

Remember heat sinks and batteries are a very poor mix.

So here's what you need. Add up all the wattage required to determine your power source.
My guess based on your posts
Blue 12 x 2.52 = 30.24W
White 6 x 3 = 18W
Total 48.24W

Now multiply that by number of hours between charges.
8hrs x 48.24W = 386Wh so you'll need *more than 125 AA 2500mAh batteries.

*they won't work as advertised, the circuitry required will not be 100% efficient either (say 84% if you're lucky)

So maybe 150 AA batteries might just work, then you've got to charge them and replace them.

Just remembered my Pedgeo Interceptor bicycle has a 480Wh LiON battery pack, you can buy one for about $800 US. Weighs 8.8lbs

Haha don't worry about the locker glowing XD I have some magnetic sheets to cover the openings, I have a locker with two openings, one on top one on bottom and they will be covered by the magnetic sheets. The lights will only be on for the eight hours that I am there anyways, during that time the hallway lights are on so even withought the magnetic sheets the glow wouldn't be noticed.

Ok, what what if I switched it up to 9v nimh?

Is there an alternative to a heat sink that won't consume as much if any?

What other forms of small cheap power sources are there?(not that 9 9v batteries is cheap XD)

wow 800?? haha thats a quite a bit too much for me...

also i don't think 150 AA batteries would leave too much room in my locker...

9V NiMH would be less energy dense than AA (a 9V usually contains 6 AAAA cells and is closer to 7.2V than 9V). Check the mAh or Wh rating in the datasheet. Remember you'll need somewhere in the neighborhood of 450Wh.

A heat sink is needed to keep the LEDs from burning up. Plus your locker is going to get warm, just like a 50W light bulb. Keeping the heat sinks cooler with the water in the tank may be an option. Either way the power requirement is going to give you grief.

Just to put it in perspective, if you were running it off a wall wart at 5V (a common voltage) you'd need a 10A rated wart (50W). That's a very big adapter.

Ok, so I have done some research and I have found that a d cell would have around 11.4 wattage hours(nimh) so if cut the lights in half(6 led blue and 3 led white) could i run it with 17 d cell batteries?(nimh)

If so is their another way to create a power source that would light it up?

Again it's all in the math. You need 450Wh, you have 193.8Wh. That's 2.3x less so your answer is you need to cut your original requirements by 2.3x

Some of the fudging is in the conversion efficiency, so the more efficient the battery to LED driver is the better. I'd chuck in the extra D cell (don't they come in packs of two) just to get it to 205Wh. Before you go buying all those batteries you should prototype driving those LEDs off a DC supply.

I don't have the LEDs yet. I plan on getting everything planned and then finally ordering what I need when all is set and verified. I don't understand how it is 2.3 times less, if I only use half of the let's I had originally planned on using wouldn't the wattage hours needed be cut in half? I tried the math and with the 6 blue LEDs and the 3 white ones I got about 24.25. Multiplying that by the eight hours I got 1943. Following that I divided that by 11.4(the wattage hours of the d cell according to the website below) and with that I got 16.92, which is basically 17 batteries. So would 17 d cell batteries run 3 white leds and 6 blue?Is my math correct? I feel like I missed or messed up somewhere.


Website I used
**broken link removed**

You could of course use a smaller battery if you had a little diesel generator in the locker to re-charge the battery.

You will of course need a timer which will start the generator in the middle of the night when there is no one there so that the noise will not arouse their suspicions.

JimB

JimB said:

You could of course use a smaller battery if you had a little diesel generator in the locker to re-charge the battery.

You will of course need a timer which will start the generator in the middle of the night when there is no one there so that the noise will not arouse their suspicions.

JimB

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That sounds a bit dangerous...
Don't deisel generators give off toxic fumes? (Also it seems a bit expensive and I think I might get in trouble if I poison the school...)

If the project was serious I would run it from a 7Ah 12c sealed lead acid battery (SLA), and have two batteries with quick change plugs. You could charge one battery overnight at home and take the fresh battery to school and swap batteries when needed.

I don't know if you would get enough light for coral but it would be enough for fish with a couple watts of LED lighting and some reflectors.

I like the sla idea. But I want to keep corals because keeping fish will require a filter and circulation pump and guess what. They'd have to be battery powered too XD
(maybe ill put in a small yasha goby or a small pipefishhalfway through the school year if the corals work since by the. The rocks and sand will provide biological filtration and they might not like current)whereas corals only require proper lighting and some flow but the ones I plan on keeping wont need flow. They do need more lights though XD OK so upon further research I found that I would only need 3 royal blues and 3 white ones. Surprisingly enough. So if I did my math correctly(again, not sure) I would require 109.4Wh basically 10 rechargeable d cells unless I can figure out a way to make that work with the sla battery.

Ok, so upon further research i figure that using the 12v 7ah battery would be the easier way to go as opposed to all of the nimh batteries. So i did the math on my lrevious postand i only need 19.4wattage hours of power. My problem is that i am unsure if this battery works like the nimh or alkalyne batteries.

Are there a different set of rules that apply to these kinds of batteries? If so how would i make it work?