I've bought a fishtank with a halogen light which I'd like to run for a set number of hours per day. The light plugs into the same adapter as the pump so I can't just put a timer on the pump, I have a plug in timer for a standard 3 pin uk plug so was hoping to use a dc adapter to run the halogen light instead of the adapter which drives the pump so my question is as follows:

The light is 12v, 10 watts. I've used an online calculator to work out I need a 12v dc adapter of 0.83 amps to power it. Does this sounds about right and could I use a power supply of a higher amp rating of say 2 amps? Does the bulb "draw" the power from the adapter or does the adapter "push" the power into the bulb?

Also does it matter which way round I connect it in terms of polarity or will a halogen bulb be fine either way round?

My final question is does anyone know where I can get a DIN socket from cheaply? Like the ones you used to find on the back of car stereos to connect the speakers.

watts = amps * volts - so the figure of .83 is correct .However this is the MINIMUM rating .Personally I'd go for something a bit more -so yes you could use a power supply with a higher current output -the current drawn by the lamp is determined by the resistance of the lamp (Ohms law -), and will not draw more than the resistance will allow.

Far as I know lamps are not polarity sensitive .

Try maplin.co.uk for the DIN socket -be cheaper going in person as the charge postage under £35 - they also do power supplies .

There's a list of their stores on line too

Thanks for the rapid response VWD!!!

and to add to that, the halogen bulb isn't polarity dependent.

Also try RS Components Welcome to rswww.com or CPC | CPC - Over 100, 000 products from one of the worlds leading distributors of electronic and related products.

Both do din plugs and plugin psu's (cpc have a good range of these)

Thinking back on the lamp - something is nagging my memory on Halogen lamps -think it's the fact that they like (from memory ) the rated voltage .If that's the case then you'd need to get a regulated supply .

Anyone confirm

as already said any incandescant lamp won't have polarity but there is polarity in terms of how to connect up an ES lamp holder as the live should always go to the centre pin

Thanks chaps - that's up and running fine now. Picked up the DIN socket from Maplins for convenience and re-cycled a 12v 2amp power supply I had lying around. Works a charm!

You may need to consider that Halogen bulbs are nearly a direct short when cold and the current to get them to start is a lot higher than you might be expecting. You may find the protection circuit on the PSU operates before it lights unless you get one designed specifically for driving lamps.

halogen lamps in general don't mention start up currents where as things like son and sox lamps do mention startup currents, halogens get up to temp/full load almost instantly.

Have you looked at any fish tank sites if you're new to it? Google maintain a fish tank. On mine I had the filter, undergravel filter and aerator and thermostat (all minimal voltage and need to run continually) off one of those very small horizontal stick thingies that are designed with that in mind and will happily run off one 13amp socket. The light, as you say, needed to be separate re timing (so I plugged the put the 3A-fused plug into a plug-in socket timer. My light didn't need a transformer, just a 3A fuse in a normal plug. Are you sure you've bought the right light kit for a fish tank?

Just wondering if we're all singing from the same hymn sheet re fish tanks and if maybe you're trying to crack a walnut with sledge hammer.

Dunno, given that elec regs change every five mins so not sure what's around now but sounds to me like you are trying to do it the hard way...

Best

Mo

Just wondering if I'm replying correctly now, as I ran mine off a double wall socket rather than only a single one. If you only have a single one, ignore my above post, well sort of as even with a four-way extension socket, you ought still to be able to use a plug-in timer with light in one (and allowing they are big and heavy but would be OK if extension lead sitting on floor), and, of the four sockets, you'd only need one other of them (so not crowding) if got a combined wiring thingy for the other items.

I know nothing about electricity, but seem to recall that four-way extension leads are better in any case than plug-in adaptors (strain on socket=misalignment=heat generated=fire, plus can be unreliable etc), whatever arrangement you choose for the light.

Anyone feel free to tell me if I'm talking through my hat

Mo

Thinking back on the lamp - something is nagging my memory on Halogen lamps -think it's the fact that they like (from memory ) the rated voltage .If that's the case then you'd need to get a regulated supply .

Anyone confirm

Yep. Running them under-voltage reduces their lifespan.

Have you looked at any fish tank sites if you're new to it? Google maintain a fish tank. On mine I had the filter, undergravel filter and aerator and thermostat (all minimal voltage and need to run continually) off one of those very small horizontal stick thingies that are designed with that in mind and will happily run off one 13amp socket. The light, as you say, needed to be separate re timing (so I plugged the put the 3A-fused plug into a plug-in socket timer. My light didn't need a transformer, just a 3A fuse in a normal plug. Are you sure you've bought the right light kit for a fish tank?

Just wondering if we're all singing from the same hymn sheet re fish tanks and if maybe you're trying to crack a walnut with sledge hammer.

Dunno, given that elec regs change every five mins so not sure what's around now but sounds to me like you are trying to do it the hard way...

Best

Mo

Yep, the light came with the fishtank (a Biube) but the light and the pump plug into the same transformer s I need to run them separately. I just needed a way to have the pump run continuously but the light on a timer - seems to work fine and only cost £1 and 9 pence as I already had the timer socket and the power supply.

Glad to hear you've got it sorted

Regards

Mo

You can buy the plug section as a seperate entity for the biorb light/pump.

i had a biorb with the intelligent led light which you can set to have different daytime lengths and just leave plugged in. the light is a bit brighter and in "night time" mode it gives a cool blue light. expensive but worth it!