how can i switch the standard light for an LED in a 'BiOrb' fish tank?

OK, i'll start by saying i know next to nothing about electronics, but i reckon this should in theory be a fairly simple hack. I Have a Baby BiOrb fish tank with 2 goldfish in. the tank is great, if a little small, and the lighting unit on the top of the tank is quite bright. i guess they use the same light unit in the small tanks as the large ones, so although its probably fine in the large tanks it's quite bright in a small one. i get the impression the fish don't like it too much as they spazz out a bit when its switched on. what i want to do is to replace the standard bulb with a less bright LED so that the lighting is more ambient and more comfortable for the fish. i've seen the moonlight ideas on here using blue LEDs which look really nice, however these tutorials are for building a setup from scratch and not for replacing components in an existing setup. the question is, what would i have to do to replace the bulb with an LED? the existing light is powered from a 12v plug which also powers the air pump; theres a central power box with two cables coming off, one for the light and one for the pump, so i guess its a parallel connection meaning theres a full 12v to play with for the light. would i need to add extra resistors or something like that, or is there such a thing as a 12v LED? what about several LEDs? (EDIT) - official literature says that the bulbs are 5w halogen bulbs. another option would be to add LEDs as a secondary light, maybe with a secondary switch for separate control to the main light. would this be easier at all? any knowledgable advice would be a great help as i've no idea where to start.

ellislake8 years ago
actually you can buy a 12v led light for it,my girlfriend has the smae tank with filter and light etc all in one unit. you just go to the shop and buy a 12v lef lamp you can buy them in a shop called maplins here in the uk,its the same as radioshack etc.no modyfying required atall
110100101108 years ago
use this wizard to design how to connect the leds

if you use higher resistor than suggested you get dimmer light

if you use a potentiometer in addition (in series) with the standard leds / resistors it will act as a dimmer. use a pot that is way higher resistance than the existing resistor (the higher pot the more you can dim your leds)

if it works on a low power transformer you may want to add big capacitor on the 12 V (25 V few thousand uF) to prevent the leds from flickering
frollard8 years ago
You'll want to check if the voltage to the light is 12v AC or 12v DC. it should say on the power supply. (The wiring is slightly different as you may want to rectify AC)

It basically means you have a whole 5 watts to deal with (tonnes for leds).

12 volts, white leds lets you run 3-3.5 volts each. (check the spec sheet).
Use http://led.linear1.org/led.wiz this calculator to figure out your led circuit
12 volts in, 3.5 volts per led, 20 milliamps per led
You can tell it how many you want to build and it will tweak the circuit. Use schematic output.