What type capacitor would i need to run more then one LED or do i even need one?

[3rmac]

wanted to know why you use capacitors with LEDs i know what capacitors do they store a charge or something like that. Well i wanted to make a led strip for my car like under the dash its a old car like a 1986 buick regal. i was thinking if the LEDs run off of 3.5v then just like 4 of them would take up one sock it [12V]. Now you get it ? Would i need a capacitor or a few to make more then just 4 LEDs to work? THANKS ANY HELP WILL BE GREAT!!!!!!!!!!!!!!!!!!!!!!

ANY HELP WILL HELP

 

[flat5]

You need a series resistor to limit current or your LEDs will burn out right away. For more LEDs put 4 more in series with a resistor but separate from the first group. Limit the current in each string to 25ma or less. Google on "Ohm's Law". Hope that's clear enough.

 

[3rmac]

thanks so much yea i know about Ohm's law but i was thinking a capacitor would store a charge cuz my Vcc is 12V(my car) and nothing more well maybe 12-14V when i have it in park its a 12V and Drive its around 13-14V. I was planing on putting like 20-40 LEDs so my thought was if i but a resistor the power(light would go down) so that why i say capacitor. am i right or wrong =]

 

[Nigel Goodwin]

thanks so much yea i know about Ohm's law but i was thinking a capacitor would store a charge cuz my Vcc is 12V(my car) and nothing more well maybe 12-14V when i have it in park its a 12V and Drive its around 13-14V. I was planing on putting like 20-40 LEDs so my thought was if i but a resistor the power(light would go down) so that why i say capacitor. am i right or wrong =]

You're wrong.

 

[3rmac]

You're wrong.

gona learn some how thanks for your input. =]
so puting them in series would be the best?
if you could tell me a blue print?
this is what i think one would like like
LED3.5V~LED3.5V~LED3.5V~1kOhm~LED3.5 and so on wont the Vcc go down, and then the lights will dim?
thanks =]

 

[Nigel Goodwin]

You have a 12V supply, so you can only place three or so LED's in series, along with a current limiting resistor - depending on the voltage drop of the individual LED's.

So you simply wire them in batches of three, each batch with it's own resistor.

 

[3rmac]

You have a 12V supply, so you can only place three or so LED's in series, along with a current limiting resistor - depending on the voltage drop of the individual LED's.

So you simply wire them in batches of three, each batch with it's own resistor.

so when i do this "batches" is that gona be in series to?
would i notice the drop in the LED?
thanks

 

[Nigel Goodwin]

so when i do this "batches" is that gona be in series to?

No, they have to be in parallel - each 'batch' of LED's and resistor is effectively a 12V LED.

would i notice the drop in the LED?
thanks

I'm not really clear what you mean by 'drop'?.

 

[3rmac]

No, they have to be in parallel - each 'batch' of LED's and resistor is effectively a 12V LED.

so there wont be a lose of light then?



I'm not really clear what you mean by 'drop'?.

like the dim in there light.

 

[Nigel Goodwin]

Work out the current on 12V, and on 14V - see what the difference is. If you think it's too much, then just use two LED's in series with a higher value resistor, this will mean less current drop from 14V to 12V.

You could use a constant current source, but it's probably not justified for your application.

 

[3rmac]

Work out the current on 12V, and on 14V - see what the difference is. If you think it's too much, then just use two LED's in series with a higher value resistor, this will mean less current drop from 14V to 12V.

You could use a constant current source, but it's probably not justified for your application.

will do thanks for you help.

i'll keep you posted on how it go's
thanks again have a good day