| Author | Topic |
|---|
Location:
boston mass usa
Registered:
November 2002
|
|
need help from u electronic ppl
|
Tue, 19 November 2002 21:16
|
 |
|
i wanna know the resistence of the mk3 supra dash bulds(from the gauges to the ones ontop of the radio) in ohms? i wanna change the bulbs completely to a hyper blue thanks in advance
|
|
|
Location:
Southern Sydney
Registered:
August 2002
|
|
Re: need help from u electronic ppl
|
Tue, 19 November 2002 21:37
|
|
wouldn't it be easier to measure the resistance of the current bulbs and then match that?
Hey, mabye it's even written on them?
|
|
|
Registered:
June 2002
|
|
Re: need help from u electronic ppl
|
Tue, 19 November 2002 22:46
|
|
|
I think you want the wattage of the bulbs, resitance varies in all globes using a fillement with temperature almost linear. Sorry cant state the wattage.
|
|
|
Location:
Montrose, VIC
Registered:
May 2002
|
|
Re: need help from u electronic ppl
|
Tue, 19 November 2002 23:19
|
|
Just make sure you use similiar wattage bulbs so as not to fry anything... or you could always be cheap and nasty and 'modify' them the 'full sik' way with a water baloon 
|
|
|
Location:
boston mass usa
Registered:
November 2002
|
|
Re: need help from u electronic ppl
|
Wed, 20 November 2002 00:30
|
|
well what i wanna do is put in leds in the place of the bulbs that are there right now
reason is cause leds are brighter and well when was the last time u heard of a led blowing
also i like the look of the blue leds and want it to match my radio
i already know that the bulbs inthere are 194 dont know what that is in ur countries but here thats a small bulb i wanna know there resistence value
|
|
|
Registered:
June 2002
|
|
Re: need help from u electronic ppl
|
Wed, 20 November 2002 00:36
|
|
|
If you want to use leds you will need a pull up resitor. I suggest 870 - 1K ohm resitor on each led would be adequate.
|
|
|
Registered:
July 2002
|
 Re: need help from u electronic ppl
|
Wed, 20 November 2002 15:03
|
|
the wattage would actually tell you what bulbs to use, but I'm sure the wirings would tolerate anything around 5W anyway, but if you want to use LEDs, you'll need a resistor as Roger mentioned,
Because the dash usually has 12v on it while most LEDs uses 1.2v, you'll need to work out / lookup the current (mA) your LED drains, then minus 12V from the voltage of the LED, eg. 1.2V, for example if your LED needs 1.2V, 50mA...
then the difference in voltage is 10.8V, the LED needs 50mA which is 0.05A, V=IR, which means R=V/I, which is 10.8 / 0.05, which is 216 ohms, that means you'll need a 216 ohm resistor or anything close to that..
or you can work it out the other way around, ie. LED 1.2V 50mA that means the LED's working resistance is 24 ohm, and you'll need 12V-1.2V of voltage drop which is 10.8, 10.8/1.2 means 9 times the voltage drop of the LED, so 9 x 24 ohm = 216 ohms
so work out your resistor using one of the above method (whichever method u understand more, you'll get the same result) and make sure you solder/join the resistor in series..
and even if you've got a regulated supply of say 1.2V, make sure you still get a resistor in line with the LED, as I think I remember, the LEDs will "decrease" in resistance as it gets hotter, so it will continue to drain more current and gets hotter until it destroys itself, so a resistor will regulate the current, and prevent the internal of the LEDs to get hot..
btw.. not all LEDs are "brighter" it's just their light output is more "concentrated", that would also mean, if you're going to be using them behind your dash, you'll need something to "diffuse" the light output of your LEDs (eg. a roughen piece of clear perspex)
almost forgot, the rating of the resistor to use can be worked out by.. 12v x 50mA = 0.6, slightly more than 1/2w, so you can use a 1w resistor etc. (using 12v assuming the resistor is taking the full load, you could use 10.8, but it's just a safety margin)..
P.S. As I work out the above, it seems like 1W resistor is too big, I think most LEDs drains 20mA, if that's the case, then 12V x 20mA = 0.24, which is less than 1/4W, if that's the case, then you could use the cheap $0.01c 1/4W from dick smith..
I hope the above clearly answers your question then I'm happy that I've helped someone..  I hope the post wasn't too long either! 
|
|
|
