Newbie needs help with Variable Brightness LED circuit

Thread Starter

Henry_1994

Joined Oct 31, 2017
1
I have recently purchased a night vision lenses for my camera and would like to test it capability,
I have very little experience with building circuits, but I want to build a simple IR LED circuit on a Breadboard which would allow me to alter the brightness of the LED.
The LED is a 2.5V Infrared.

Can someone help me Please?
 

dl324

Joined Mar 30, 2015
16,845
Welcome to AAC!

The simplest circuit would be a potentiometer in series with the LED, with another series resistor to limit the maximum LED current to something sane.
 

wayneh

Joined Sep 9, 2010
17,496
The pot should have a range from zero to 5K or 10K ohms, and a linear (not log or audio) taper. The LED will be nearly dark at 1K, and you could use a 1K pot or even a 500Ω pot if you don't care that the LED doesn't go completely dark at the lowest setting.

The series resistor mentioned by @dl324 is crucial to prevent destroying the LED when the pot is turned to zero, which Murphy's Law dictates is inevitable.

If you want to expand your test to an array of LEDs, a pot is no longer practical. I'd recommend a pulse-width-mudulation (PWM) LED dimmer you can find ready-made on eBay for next to nothing.
 

philba

Joined Aug 17, 2017
959
Do you have the LEDs yet? I'm thinking you don't. For an IR illuminator, you will want a fair amount of light. This means either a high(er) powered LED or a bank of lower powered ones.

PWM is one way to control the brightness. Though, make sure you use a PWM rate well above 120 hz as you will get strobing artifacts with motion.

Some constant current LED controllers also support current control which allows you to dim without using PWM. For photography/videography, this is much preferred.
 
Top