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Apr 10, 2011 16:14:30 GMT
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Hello there.
Just need a quick answer really. Cos I'm modding my bike, i'll be moving the brake light, so i need a stand alone number plate lamp.
Cheap LED ones are readily available, but they all claim to be for 12v, wheras my bike is 6v.
Whats the deal with this? would they still work just be a bit more dull?
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Apr 10, 2011 21:03:10 GMT
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Pretty much. Imagine a torch where the battery has run down.
Its the other way round that makes things break!
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Apr 11, 2011 13:31:14 GMT
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Going back to GCSE physics here so I may be wrong. V=I*R So, you know your voltage is 6Volts, you can measure your Current with a multimeter (I). You should then be able to work out R and swap out the resistor for a differently rated one. At a guess, half the impedance should do it. Here's how you decode the coloured bands painted ont he resistor to work out what impedance they are: www.csgnetwork.com/resistcolcalc.htmlI could be spouting rubbish but it kind of makes sense to me. HTH, Rich |
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Apr 11, 2011 21:41:39 GMT
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absolutely correct. a LED is LED, it's the dropper resistor that determines the working voltage.
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Apr 11, 2011 21:47:47 GMT
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Just swap the resistors and I'm ok then yeah?
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Not a bad idea, ill have to see if it'll fit!
Cheers for those, given me some food for thought.
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To give you an idea of how it fit.. The bolt in the back of the lilttle wipac, Went nicely thru that bracket you made for the speedo. My little temporary MOT lamp holder for the puch  If you want any measurements of it let me know  |
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Apr 12, 2011 10:56:22 GMT
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Ah thats ok then! at least my 'professional' work on the bracket didnt go to waste Nonetheless its fine now, my dad found me a stand alone old chrome lamp, so i'll just pop a 6v bulb in there and it'll work nicely. Just gotta get myself a new brake lamp now and I'm sorted. |
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Apr 12, 2011 18:39:26 GMT
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Just in case you find it useful, here's the full answer:
An LED will have a fixed voltage drop across it, due to its design. For red LED's, it's around 2 volts, for white, around 4 volts.
The resistor is to protect it from excess current. To work out the new value of the resistor, you need the voltage across the resistor and the current going through the resistor.
Measure the current drawn when running the LED light on 12v - .this will stay the same when running on 6v
The voltage across the resistor will be the the supply voltage minus the LED voltage. Given that you're running them on 6v, this will be 6v - 2v.
Finally, use R = voltage (which is 4v) / current (which you measured).
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Jan 16, 2020 14:40:03 GMT
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Hello there. Just need a quick answer really. Cos I'm modding my bike, i'll be moving the brake light, so i need a stand alone number plate lamp. Cheap LED ones are readily available, but they all claim to be for 12v, wheras my bike is 6v. Whats the deal with this? would they still work just be a bit more dull? I bought an old fibre optic lamp using a 6v halogen bulb and replaced it with a 12 volt led. It made no difference on the brightness. In fact the led was alot brighter. |
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