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Modifying a fish tank hood?

Discussion in 'General Electronics Discussion' started by Toleman, Sep 4, 2010.

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  1. Toleman


    Sep 4, 2010
    Hi people, new here :D

    I thought I would see if anybody could help me out regarding the internal wiring.

    So the hood has mains incoming which goes to a PCB. The PCB is split into two halves, a mains half and a 12v DC half.

    The lid incorporates two 36w fluorescent lights and these are switched via 2 of the 3 switches on the top of the hood. The lid also uses 2 12v fans which BOTH come on if 1 or 2 lights are switched on the lid. These are triggered by double switch double pole switches on the lid - I think thats what they are called.

    The 3rd switch on the top puts the LED moonlights on and these are 12v also.

    As the mains enters the PCB it splits to two and goes off to the switch. The return comes back to the board and to some screw connector blocks. Then the wires go off to the ballasts and in tern to the fluorescent tubes.

    At the same time the mains incoming leaves the board and goes to a 12v transformer. The returning 12v occupies half the PCB for fans and LED's. There is a switch wire which goes to the other poles of the 2 switches as pictured below. (right side of the 2 right switches).

    This then comes back to complete the circuit for the fans.

    Now people have done a modification on this lid where they disconnect the ballasts and wire them into seperate plugs. This totals to 3 plugs doing a fluorescent light each and the fans and LED's on the original plug. Then use 3 timers to bring them on at staggered intervals. (you then leave all 3 switches in the on position)

    Still with me... :confused:

    I'd like to keep the leds on the original switch and bring the fans on with the fluorescents. I'm guessing I would need to use a relay fired by each of the two main lights. Then break into the 12v switch wire and connect these to both of the relays through the switch terminals.

    This sound about right? I would need a relay which can use mains for the magnet side. Any suggestions?

    The thread where somebody moddifies their hood but the short cut way:

    Any more images needed then let me know.

    Thanks, Chris
  2. Leighcusack


    Sep 9, 2010
    Ok... I'm not one hundred percent sure if I understand you on this one. Some more pictures showing the complete wiring would have been helpful.

    So tell me if I got this right.
    The two right hand switches in the photo control each light? From mains power?
    The right hand pole of each switch controls the 12 volt fan.

    The left hand switch controls the LEDs from the same 12 volt supply as the fan?

    Ok.. Assuming that is right.

    The easiest way would be to duplicate the transformer part of the curcuit. Since I assume at the moment the 12 volt supply is fed from one of the power leads to the wall. Ifvyou want to keep the 12 volt units.

    Why don't you just replace the fans with mains powered AC units? That way you can install them parallel with the lights. They would only be lighty loaded so I can't see any dramas.
  3. Johnny5


    Sep 10, 2010
    Do you want to turn on,off one flourescent at a time along with one or both fans, more info would be helpfull.

    Also are you looking to cycle the fans without having the led on?
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