Electronic Geeks Look Here!

[Schweppy]

Trying to work out what size resistor I would need to put in parallel with my Cups single LED festoon interior light so that it comes on when opening the doors.

The standard bulb is 12v 5w and i'm guessing the LED replacement is 12V and a much lower power.

 

[Schweppy]

bumppppp

 

[Da]

A resistor will not help dude, who told you that you needed one of those? :S

 

[Schweppy]

My uncle said if I work it out then a resistor in parallel with the LED should act like a normal bulb.

 

[Da]

Hmmm...well maybe, hang on a few minutes and I'll look into it.

 

[Gumby]

http://cgi.ebay.co.uk/RENAULT-CLIO-...ryZ10410QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.co.uk/Renault-Clio-...ryZ10410QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[Schweppy]

Already been there dude! Had 1 off Da! Doesn't fit!

 

[Da]

:dapprove:

I've had a dig about mate and I cannot see how fitting a resistor across the LED would depolarize it?
Did your uncle offer any explanation?

 

[Schweppy]

Ummm no but i assumed and told him that it was to do with the led not detectin the drop in voltage when openin a door and thought that if u make an led have roughly the same resistance as bulb it would work. Nothin to do with being polarized.

 

[Da]

Have you tried the LED in your glove box or boot light mate? They're the same size, try it both ways and check it works in both positions.

 

[ditz]

you cant depolarize an led with a resisitor - you can however buy leds that work either polarity.
only way to do it

 

[Schweppy]

Have you tried the LED in your glove box or boot light mate? They're the same size, try it both ways and check it works in both positions.

LED works fine in the boot and glove box and in the interior light. The interior light just doesnt come on when opening the doors, only works when turning it on at the switch.

 

[Schweppy]

you cant depolarize an led with a resisitor - you can however buy leds that work either polarity.
only way to do it

Is it defo to do with polarity? Im pretty sure that if it works with the switch its just a voltage drop when the doors open.

 

[Da]

Have you tried the LED in your glove box or boot light mate? They're the same size, try it both ways and check it works in both positions.

LED works fine in the boot and glove box and in the interior light. The interior light just doesnt come on when opening the doors, only works when turning it on at the switch.

I'm 99% sure it's because the LED is polarized.

My suggestion would be to turn the LED round in the courtesy light then see if it only works with the doors and not with the switch.

 

[Schweppy]

Will go and do it now! lol

 

[ditz]

well i've never really looked in to it on a clio, but how alot of them work is you have to live feeds if you like going to each leg of the bulb, open the door and that side lives up (earths out through the other side) and vice versa
hence why it only works one way or the other
simple way to test is if it dosnt work when opening the doors turn the bulb round see if it then works with doors open but not on switch

 

[Schweppy]

 

[ditz]

lol, easy this electrical lark isn't it

 

[Schweppy]

LEGENDS!!!!!!!! It works when the doors open now and goes on and off with the central locking and goes off after 10 seconds of doors being shut!

It doesnt work when you use switch but i never use that anyway, well rarely! Lot better though thanks guys!

 

[Da]

:approve:

See we got there in the end hey Andy? It's a polarized LED

 

[Schweppy]

How much effort did we/YOU got to LOL!

Seriously tho, thanksssssssssssssss.

 

[Schweppy]

Oh and i did my number plate light and side lights with LEDs today too! Looks awesome now!

 

[Da]

Join the club

Oh and your welcome pal

 

[Marky_]

So after all this time you didn't try flipping it around?!
*shakes head*

I thought the problem was you were trying to make it work both with the doors and the switch.

 

[Schweppy]

Sowwwwwyyyyyyyyyyyyyyyyy! lol

Working both ways would be good.......

 

[Marky_]

Lol. I got all excited and thought someone sorted them both ways. It's impossible i tell thee!

 

[Jamie Mac]

I know this is an old thread, was changing out my interior bulb today and had the exact same problem. I got a multi meter and measured the voltage and found that when switching from door mode to light on it switches the polarity.
My solution to this problem is to get two led lamps hot glue gun them together and solder them to each other in opposite polarity. So therefore when the light is in door open mode one of the led lamps light up then when you switch to light to always on the other led lamp lights up due to the polarity being different, hope that makes sense and it is an easy enough fix if you have basic soldering experience.
Image below of the final led lamp that works!!!
p.s on the image the polarities are labled on the leds just follow the wires and you can see what goes where.

 

[McGherkin]

Yeah, there's a few ways to skin the cat. You could do as above, or use a seperate bridge rectifier, or use the two bulbs in series with a diode across each!

Easiest option for those who aren't great with the soldering iron is to swap the unit out for one with a map light. You could then put an SMD panel in it as well for extra power (I did a thread a while back, called Joy of LED improve the interior light tenfold, or something along those lines.)