Anyone know what happens if i don't use the resistors on the led's?

your doors fall off!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

oly joking depending on what the leds are rated at eg 9 volts needs the resister to drop the voltage so you don't blow them

 

hth

Bugger, i aven't used any, couldn't find any anywhere! Don't know what voltage they are! Will they work for a little while? Or blow straight away?

Bugger, i aven't used any, couldn't find any anywhere! Don't know what voltage they are! Will they work for a little while? Or blow straight away?

 

If they're 'normal' LEDs, they'll probably last about 30 seconds at a guess....

But you can buy LEDs with built in resisters - so can be directly connected to a 12v supply. If you have this kind - you'll see a little dark dot under the anode inside the casing.

 

Simon.

Here ya go

 

Calculating an LED resistor value

 

An LED must have a resistor connected in series to limit the current through the LED, otherwise it will burn out almost instantly.

 

The resistor value, R is given by:

 

R = (VS - VL) / I

 

Where:

 

VS = supply voltage

VL = LED voltage (usually 2V, but 4V for blue and white LEDs)

I = LED current (e.g. 20mA), this must be less than the maximum permitted

 

(these values may also be supplied with LED)

 

If the calculated value is not available choose the nearest standard resistor value which is greater, so that the current will be a little less than you chose. In fact you may wish to choose a greater resistor value to reduce the current (to increase battery life for example) but this will make the LED less bright.

 

Full details are here:

 

http://www.kpsec.freeuk.com/components/led.htm

Ok, guess i'm leaving that till i can get resistors then! But, on the upside, i think i've finally fixed my speedo, looks like the muppet that changed the clock to MPH didn't connect the positive wire to the right place!

1 k/ohm :D

theres a link in the write up youve posted in for the right ones an where to get them

 

HTH

Anyone know what happens if i don't use the resistors on the led's?

 

 

Hi Mate, most of the coloured LEDs you can buy will need a resistor of about 470 - 600 ohm (the less the resistor the brighter the LED).

 

If you run them without resistors they will blow almost immediatly

 

Maplin will do you them for a couple of pence each...