Dimming LED ribbon for aquarium lighting

Discussion in 'The Projects Forum' started by sam smyth, Feb 8, 2014.

  1. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    Hi, this is my first post. I've joined the forum looking for some advise on this particular project and also to try and learn more about electronics and circuits. I have a limited understanding so please keep that in mind in your response - I really appreciate any help, thanks for taking the time to read.

    My project is to convert an old television into a fish tank. I've hollowed it out and got the tank inside but now I want to consider lighting. What I would like to do is to wire up some of the televisions control knobs so that they control the lights. I've attached a picture of the knobs from the front and the back and also removed so you can see what they look like. they are labelled picture, pull on/vol, colour, & hue. The pull on/vol is the only one that can click out as a switch.

    I would like to put in red, green and blue LED lights (probably the 12v ribbon sort)

    Ideally this is what I want the knobs to do : You pull the on/off knob and all the lights turn on, you twist the picture, colour or hue knobs and they each dim a different LED strip, So you can dim or brighten the three colours independently of each other. The idea is you can sort of control the colour of the aquarium as if it were a TV screen.

    I have been reading a bit about dimming LED's and it looks like this might be possible either by using some current resistors or pulse width modulators but i don't know anything about these or how difficult it would be to attach them to the tv knobs. I realise the resistors (if thats what they are) in the picture will have to be removed, and the correct type added. But will I be able to attach it to the knob?

    I also don't know how i could wire it so that It only has one mains plug, rather than 3 separate 12 v power supply plugs.

    If you can shed some light on how I can achieve this or maybe point me in the direction of the right resistor or 'PWM' I might need to dim 12volt LED ribbon I would be extremely grateful.

    Sam
     
  2. Metalmann

    Active Member

    Dec 8, 2012
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    Old TV aquarium?:cool:

    Cool idea, I'm sure some of these guys will lend you a hand.
     
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    Those LED ribbons are not anywhere near bright/powerful enough for an aquarium.

    Aquarium lighting isn't cheap, and you would spend a good bit more trying to build something suitable yourself rather than just buying a reputable off-the-shelf brand.

    Your aquarium lifeforms need the proper spectrum of color to thrive.
     
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  4. burger2227

    Member

    Feb 3, 2014
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    I recently got an LED aquarium light that uses 24 bright SM LED's with a switch that turns all on, off or 2 blue LED's for late night. Looks pretty cool.

    12 volt ribbons would work if they are bright enough or you could get some RGB LED's so that each control would dim Red, Green or Blue parts of each one. Some light strings come with remotes that can do the dimming and color changing. No soldering at all! Look on Ebay for remotes.

    http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1313.TR0.TRC0.XRGB+led+strip+with+remote&_nkw=RGB+led+strip+with+remote&_sacat=0&_from=R40
     
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  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Are you sure?

    Some of those new high intensity LED ribbons are pretty amazing. Especially if you stack up a few ribbons and maybe different colours.
     
  6. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    Thanks for the replies.
    SgtWookie, I'll keep that in mind maybe i could supplement with a fluorescent tube on the top. There won't be any plant life and they are just goldfish so I think with a bubbler and daylight from the front of the tank the fish will be okay its more a matter of the tank being illuminated. I was thinking that if i got a couple of meters of each colour i could line the top and sides of the the casing around the tank. (as RB suggests)
    Burger, thanks for the tips and the link, I've had a look at the remotes they are pretty good but I am particularly keen to use the tv knobs to control the dimming, it's this point in particular that I am hoping to find out how to do. I don't mind soldering or buying the parts but at the moment I don't know what it is that i need
     
  7. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    Last edited: Feb 9, 2014
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Just depends on whats in the tank..
    A saltwater "coral reef" or planted freshwater setup requires substantial lighting power.. while a "fish only" tank just needs lights to see/enjoy the fish..
     
  9. burger2227

    Member

    Feb 3, 2014
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    I'm not aware of any Growlux LED's, but you have all colors in white ones. How plants will fare is another story. LED's could be added to an old Growlux lighting system pretty easily too. 8 hours of light a day should be enough. I've raised tons of fish, not many plants.

    The first thing you need to do is determine how many LED's you want to use and how much current they will use before anybody can help you design a working circuit. I mentioned RGB because you wanted to use 3 controls. A 555 could run a PWM for each color in a RGB LED. The remotes just take out a lot of the design problems.
     
  10. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    Burger - I've been doing some more research, your right about RGB being the way to go, I had mistakenly thought of running 3 separate strips (one red, 1 blue, 1 green). I am thinking of getting a 5 metre RGB LED strip with 60LEDs per metre. (each LED contains RGB) I think the current is 400ma per RGB channel per metre, so for 5 metres thats 2 amps per channel right?
    I still don't fully understand but I've read that you wire each channel into a transistor (non or n channel MOSFET) and then into PWM to dim each channel.

    But could it also work to use a potentiometer? From the look of it thats what is already wired into the tv, so If I took those out out and replaced them with A potentiometer for each channel, in the correct resistance (I don't know what that would be yet) It looks like it would be easy to connect the potentiometer knob to the television knob through the same hole.

    I realise that this seems a pointless thing to do when the remotes do this so much easier and with more controls but It's important to my design to use the televisions original knobs.

    cheers for your responses
     
  11. burger2227

    Member

    Feb 3, 2014
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    I understand perfectly. I once restored an old TV box myself. It shocked me too and I should have known better. I fixed TV's as a hobby...

    Here is a 555 circuit with a 50K potentiometer you could probably substitute for the old control. If the old knob is a half shaft type it should slide on OK. Could you show a picture of the control and knob?

    http://www.reuk.co.uk/LED-Dimmer-Circuit.htm

    [​IMG]

    You'd need one for each color string or LED lead. An RGB LED would have 4 leads with one common anode or cathode. The transistor would only complete one anode or cathode circuit per color.

    One note. The circuit cannot turn the LED's off completely. You could use the TV's on off switch for that.
     
    Last edited: Feb 9, 2014
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  12. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    Thanks a lot this is really helpful.
    yes i was quite worried about getting a shock too!
    The knob is a D shape, I've attached a picture.

    So If I understand you and the article you linked correctly, I should be able to achieve what I'm trying to do by using for each colour string or LED lead an NPN transistor and a 555 timer which i can wire to a 50k potentiometer which i can (hopefully) attach to the Tv knob.

    does that sound about right?

    *edit*

    I think I've oversimplified that - as I mentioned before I don't know very much about circuits but this is very useful I will study the circuit diagram above and learn what everything means
     
    Last edited: Feb 9, 2014
  13. burger2227

    Member

    Feb 3, 2014
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    Yes you can! Here is a better example of what each color circuit would need:
    [​IMG]

    The wiring is shown for RGB LED's with a common Anode. The series LED's in between are for wiring a string of lights.
    It just shows how the green G circuit would be wired either way.

    Many potentiometers come with full round shafts, but they can be filed down and cut off easily as most are aluminum.
     
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  14. sam smyth

    Thread Starter New Member

    Feb 8, 2014
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    so for each colour circuit other than the 555 timer, the NPN transistor and the 50k potentiometer I also need 3 capacitors, 2 resistors and 2 diode's is this correct?

    good tip on filing down the shaft i was thinking of using glue or something
     
  15. burger2227

    Member

    Feb 3, 2014
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    You will need to create 3 identical circuits, one for each color whether you use RGB LED's or strings of LED's. The 3 PWM circuits will allow you to dim each separately. Otherwise all 3 would be the same brightness and you could not change the color of the lighting, just the brightness.

    IE: You will need 3 of everything including the 555 timers.

    One note. The circuit cannot turn the LED's off completely. You could use the TV's on off switch for that.
     
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