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General => The garage => Topic started by: VeeDubGTI16v on 03 July 2004, 15:47
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im not too electrically minded so can anyone tell me what sort of circuit i would have to make to power 4 LED's instead of the indicator bulb ???
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buy the complete replacement indicator unit you cheapskate :P ;D
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nah i want to put some led's in the headlights because i dont think i can fit a standard indicator bulb in there.
i got no indicators in my big bumpers ;)
just thought theres probably some resistors or sumething that needs to go in the circuit ???
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any electricians in the house ???
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buy the indicators and cut them up, but yeah they will ahve a resistor or else they will blow up, ask nick he is doing it at uni
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lol @ veedubs, dont you two live next door to each other ? ;D
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Find out the current that the circuit will use, then use Ohms law to give the value of th resistor: R=V/I Where R=resistance, V=Potential Difference, and I=Current. Hope this is helpful!
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lol @ veedubs, dont you two live next door to each other ? ;D
err, near enough :-[
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Find out the current that the circuit will use, then use Ohms law to give the value of th resistor: R=V/I Where R=resistance, V=Potential Difference, and I=Current. Hope this is helpful!
Eh? ???
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lol @ veedubs, dont you two live next door to each other ? ;D
err, near enough :-[
I meant that you could shout across the garden fence rather than going on the t'internet ! ;D
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Find out the current that the circuit will use, then use Ohms law to give the value of th resistor: R=V/I Where R=resistance, V=Potential Difference, and I=Current. Hope this is helpful!
Eh? ???
Sorry, which bit don't you understand?
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its cool i understand. ;)
do i just use one resistor run in series with the 4 led's ???
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buy the indicators and cut them up, but yeah they will ahve a resistor or else they will blow up, ask nick he is doing it at uni
Ahem, i doing mechanical, bollox to electrics!!!
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its cool i understand. ;)
do i just use one resistor run in series with the 4 led's ???
Cool, sometimes i'm not very good at explaining things!
What do i mean SOMEtimes, Never!
You'll probably need two resitors, one for the left, one for the right. Is that what you meant? ??? :-\ You want to aim for about 6-7V, no more though. And its V important to have them the correct way round, ie +ve with anode, not cathode, as LEDs can't be reverse biased.
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buy the indicators and cut them up, but yeah they will ahve a resistor or else they will blow up, ask nick he is doing it at uni
Ahem, i doing mechanical, bollox to electrics!!!
Whats wrong with electronics?? ;) :P
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its confusing ;D
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yeah, you can't see whats going on!!! ???
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This is true i suppose!!!
Had a (hopefully helpful) thought for you. Wire up the diodes, and then use a tansformer and a potentiometer to find out the best operating potential. Enough to be at their brightest, but not too much they start to go funny colours!! ::) I reckon it'll be about 7V, maybe less, probably between 6 and 7. Then us this in the formula. It should all work, let me know if if it doesn't, and if it does, wanna see how good it is!
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ok cheers for help jmallows. im not gonna do it just yet, ive got loads of stuff to do first before i relocate the indicators (like finish the bumpers :-[ ;D)
cheers
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if you are buying the LED's off of somewhere that specialises in selling them, or an electronics company like maplin (www.maplin.co.uk ;) ) then they will have things such as forward current and forward voltage noted. Then from R= V/I
Supply Voltage(V) - LED Forward voltage(V)
LED Forward current(A)
Where the supply voltage is errrr... 12 Volts... it being a car!
Always go for a slightly larger (not overly larger!) resistor than needed to protect them a bit, and you need the highest candela rating you can get.
anything else? oh, ive heard that if you gently file the tip of an LED the light will diffuse a bit better. dont try it unless you've got a spare though! and the potentiometer is a good idea... as long as you are very careful, IIRC theres a very fine line between maximum brightness and burning it out! And they need to be the right way round... hence forward voltage ;)
HTH! 8)
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ill just get a handful and play with them then cos they only cost about 20p each from uni, and resistors are about 15p ;D
and which lights would you peeps put the indicators in, the headlights or inner spotlights ???
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Yeah, thats true, except it wont be 12V it'll be the voltage that yo want to use, hence the resistor to drop it from 12V??
And they need to be the right way round... hence forward voltage
Thats what i meant about "the right way round" ::) ;D My non-technical version!! Although i did say they can't be reverse biased, which is the same!
which lights would you peeps put the indicators in, the headlights or inner spotlights
Both!! If you do go for one, then the inner, or better yet..... the fog lights, if you have big bumpers?
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No, the supply voltage is 12V!! take away the forward voltage of the LED and you have the voltage you need to kill off with a resistor ;)
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nope fogs have been smoothed too ;D
i think i might do the outside ones as there is the most length difference between them so they will be more distinguishable when im indicating. spots might be a bit too central ??? i like the idea of having them in bith tho ;D
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No, the supply voltage is 12V!! take away the forward voltage of the LED and you have the voltage you need to kill off with a resistor ;)
You sure?? I'll trust you, as this is ne of those electronics things i often had trouble with!! ::) I suppose if its tested before its put in, it wont be a problem.
i like the idea of having them in bith tho ;D
;D At least someone likes my ideas, don't happen often!! :'(
If your going to get the diodes cheap from somwhere, i'd grab a load, test a few different circuits (keeping them, so you can compare) and then with the final circuit happy, get some high intensity ones, just to make sure! The forward voltage shouldn't be much different, but will obviously need to be considered. Glad to help!
(if its helped!)
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nope fogs have been smoothed too ;D
Shame, thats personally where i think they'd be best!!
I suppose, you could drill a few holes down there, say 6 in a nice pattern, and mount the diodes behind a black membrane stuff, so it looks black with no lights, then lights up behind it. Cool!! Saw something similar on a camper, had a totally black front end, headlights were hidden behind it! (it was a newer camper, D,E?, so had the flat front end)
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im gonna just drill out 4 holes in the ehadlights (outers) and have 4 led's for each indicator bulb i think.
i dont want to put anything into the big bumpers cos they need to be smoothe ;D i think relocated indicators (indicator units) looks a bit naff to be honest, thats why i want to hide them in the headlamps. ;)
will 4 high intensity led's be visible when the headlights are on? or will i have to make the headlights flash with them? and is this legal????? ???
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it might be worth you going down the scrappy and getting a spare light, to play with, so you can find out if four high intensity's will be bright enough with the lights on.
I also havent thought about how more than one LED in series will affect the resistance. I can't at the moment because I've not done any work for my degree in whats approaching three months and have forgotten most of it. will ponder it slowly for a while and get back to you if anything strikes me! ::) ;D
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ok cheers for help jmallows. im not gonna do it just yet, ive got loads of stuff to do first before i relocate the indicators (like finish the bumpers :-[ ;D)
cheers
Yeah man you been doing them for ages now!!!
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I had the same thought as you jazz, i reckon they would be better in parallel because then they'll all be the same brightness! But that might make the wiring loom a mission to build.
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Hi, do you really need leds ? why not consider the low voltage (ie 12v) metal base sub miniature bulbs from Maplin - you could spray or paint them whatever colour you want ? on the other hand they also sell 12v coloured subminiature bulbs in a fetching range of 4 colours (also 12v).
Lets say you really want an led. Lets say you go for one with a forward voltage of 2.2v and a forward current of 25mA. The resistor you have to put in series needs to 'drop' a voltage of 12 - 2.2 = 9.8 volts (lets call that 10 volts). The current passing thru the resistor will be the same as the led, ie 25mA (1mA being a 1/1000th of an amp). so, the value of the resistor is (10 divided by 25) then multiplied by 1000, ie 400 ohms. You can't get a resistor of 400 ohm. Get the nearest from maplin which will be 390ohm. You need to get one that will dissipate the heat generated by the current passing thru it - calculated as volts times current. In this case 10volts times 25mA = 250mW (that's a quarter of a watt).
so, If you decided to buy that particular led you would need to buy a 390 ohm resistor at a quarter watt capacity to put in series with the led. Similarly for each led you buy, and don't forget to wire it to the correct side of the supply fuse.
Consider using the conventional bulbs - easier. Regards, yt
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Not wishing to tread on any toes here but...
Maplin supply LEDs that are designed to fit straight onto a 12V supply. I had a couple of these on my old motor wired in to create a 'dummy' alarm system on an old banger.
Maplin Cat no CJ68Y is a 3mm Yellow LED with a built in resistor and are 18p each.
The ones I used were 5mm, red and didn't generate any noticable heat even if they were left on all night....
Or I could be barking up the wrong tree (or just barking!)
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i only wanted to use the led's because they were small and would be easy to mount in the headlights, but the wiring does seem a little confusing.
would i only need one do you reckon in each headlight.
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I doubt that one 3mm LED would be anywhere near bright enough.
However for 18p a shot it might be worth getting 5 or 10 from Maplin and wiring them in series and see what happens.
If the 12v ones work (awaiting the blessing of a sparky here...) wire 5 up, rig up a temporary connection and see how it goes. Of course there are things like current drain on the existing circuit to consider but at 8.5 mA per LED, I don't think this would be a problem (again a more qualified electrician should be able to confirm this).
To be honest I had thought about a side repeater made out of LEDs around a VW badge (in the BMW Z4 style ) as I think a ring of LEDs would look quite good as a replacement for a bulb!