led/resistor for highest output?

[circa27]

Im putting IR leds for a light source on my reverse camera on my car. so the voltage is 14.4 and the led forward voltage is 1.6 with 60 mA draw. total of ~90 leds ( i can add/subtract by a few if needed)

since R=V/I could i just have chains of 9 leds (R= (14.4-(9*1.6) / 60mA = 0) without resistors?

also, would it make a difference if i wired the chains all coming from the same wires in parallel ( **broken link removed** ) or if i wired them in a series of parallel chains of 9?

i just want the highest output possible and i would like some advice so they dont burn out too fast. power supply is not a problem

thanks!

 

[audioguru]

Infra-red LEDs are 1.6V but are invisible.
Red leds are about 2V.
But for a camera don't you have white LED? They are about 3.5V each.
If the LEDs are ordinary 5mm in diameter then their max allowed current is 30mA and they are typically used at 20mA.

Your car's battery is from 11.8V to 15V. When charging at 15V then three 3.5V white LEDs in series have a total of 10.5V and the remaining 4.5V with a current of 20mA requires a 225 ohm current-limiting resistor. 220 ohms is the nearest common value and its power rating should be 1/4W. Then you have one string. Use as many strings as you want.

 

[circa27]

false, infrared is invisible to us but not to cameras. also they're 850 nm and give off a slight dim red color that we can see.

they are 1.6v, i dont have white and have a peak of 120 mA with, as i said, continuous current draw of 60mA.

my car battery is exactly 14.4v.

if you dont know how to help me thats fine but if someone does id appreciate a little advice now that we've double checked the facts.

im not trying to be rude but if i post values for an accurate result then its unnecessary to question everything i said. i dont have white leds

thanks

 

[ericgibbs]

hi Circa,
You cannot connect an LED chain, without a series current limiting resistor, directly to your vehicle battery. They will most likely burnt out.
The usual way for strings, is to calculate the series resistor assuming, the highest possible battery voltage that will not exceed the LED's current rating.
To chose the number of LED's in the string, assume the lowest battery voltage that will exceed the total voltage drop across the LED string.

eg: say the battery minimum is 11V and the LED Vfwd is 1.6V = 6.8 LED's so use 6 LED's in the string =9.6Vdrop.
Next to ensure that the 60mA LED rating is not exceeded when the battery is say 14.4V, would require a series resistor of [14.4v-9.6v]/0.06 = 80R

At the lower battery voltage of 11V, the LED current would be 1.4V/80 = 17.5mA.

A way to overcome this change in LED current would be to use a 60mA constant current source.... OK.?

 

[audioguru]

On the other website you posted the spec's for the IR LEDs. It says they are not visible and are good for remote controls, not good for an IR lightsource.