Corsa_Mel
Member
Registered: 15th Oct 01
Location: Sale, Greater Manchester
User status: Offline
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I've got some blue leds in my mfd and one has blown.
Just wondering all these people that are just using resistors to limit the voltage (like me) have a big chance of them blowing.
For example the voltage fluctuates around 12v so my resistors will probably be calculated for a 12v supply, but if the leds get 14v then pop they go.
Isn't this the case? is there anything else that can be done?
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cobra148
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Registered: 27th Oct 01
Location: Here in front of my monitor.....
User status: Offline
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Might be dependent on the spec of the leds you have. A car alternater will usually run about 13.8v but can peak around 15v at times. I've had leds fitted for about 8 months now with no problems. In fact, even while trying different projects with them, I've never yet managed to "blow" one, maybe just lucky.
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kev_corsa
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Registered: 7th Nov 02
Location: Newport, Uni in Bristol
User status: Offline
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the voltage in my corsa c goes up to 14.4V when the engine is running.
to work out the resistance you need to use for your led, you need to know two things : 1. the voltage of the LED, 2. the forward current of the LED.
(eg. if the voltage of the LED = 3.6V, and the forward current is 30mA (0.03A))
(14.4 - 3.6) = 360 ohms
--------------
0.03
i dont think u can get a 360 ohm resistor, so go for the next value higher.
do this and they shouldnt blow for ages.
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kev_corsa
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Registered: 7th Nov 02
Location: Newport, Uni in Bristol
User status: Offline
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o yeh, make sure the resistors have the correct power rating as well
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