Hi Everybody,
My obsession with LED have brought me to this crucial task of finding actual VF and IF rating of a LED.
I decided to go for it because a article I read states
"Most white LEDs are typically listed as VF = 3.2-3.6V, IF = 20 mA; their luminous intensities can range from 3,000 to 30,000 mcd with associated ascending prices. Also keep in mind that not all LEDs are created equal. Even if you buy the same batch of LEDs from one source, each LED may have slightly different forward current under the same forward voltage; hence, different brightness. For this reason, it’s better to measure each LED’s VF and IF before using them. Herea is a simple regulated power supply circuit to do so.
![Voltage Regulation LM317.jpg Voltage Regulation LM317.jpg](https://www.electro-tech-online.com/data/attachments/32/32316-fb0a6b4f54026d262ae05cf9ef4f3541.jpg)
It uses the LM317 regulated IC. Its output voltage VO (volts) can be approximately calculated by the following formula: EQUATION Vo = 1.25 (1 + R1/R2)
For instance, using R1 = 500Ω, trimmer potentiometer and R2 = 100Ω, the highest output voltage should be VO = 1.25*6 = 7.5V. Therefore, you can reduce the trim-mer resistor value to get any regu-lated voltage between 3.0V to 4.5V at the output for your experiment. "
I think it is simple enough(geek wise) to accomplish my goal, but How in do I proceed practically. In layman terms, to say, I have got LM317, 9V Dc 500 mA power source, the 500 ohm pot. and 100 ohm r2. Now where do I connect the led, what to measure and at what point etc. etc. in order to get the Vf and IF of a given LED.
Or there is some other better way out also ?
Thanks
My obsession with LED have brought me to this crucial task of finding actual VF and IF rating of a LED.
I decided to go for it because a article I read states
"Most white LEDs are typically listed as VF = 3.2-3.6V, IF = 20 mA; their luminous intensities can range from 3,000 to 30,000 mcd with associated ascending prices. Also keep in mind that not all LEDs are created equal. Even if you buy the same batch of LEDs from one source, each LED may have slightly different forward current under the same forward voltage; hence, different brightness. For this reason, it’s better to measure each LED’s VF and IF before using them. Herea is a simple regulated power supply circuit to do so.
![Voltage Regulation LM317.jpg Voltage Regulation LM317.jpg](https://www.electro-tech-online.com/data/attachments/32/32316-fb0a6b4f54026d262ae05cf9ef4f3541.jpg)
It uses the LM317 regulated IC. Its output voltage VO (volts) can be approximately calculated by the following formula: EQUATION Vo = 1.25 (1 + R1/R2)
For instance, using R1 = 500Ω, trimmer potentiometer and R2 = 100Ω, the highest output voltage should be VO = 1.25*6 = 7.5V. Therefore, you can reduce the trim-mer resistor value to get any regu-lated voltage between 3.0V to 4.5V at the output for your experiment. "
I think it is simple enough(geek wise) to accomplish my goal, but How in do I proceed practically. In layman terms, to say, I have got LM317, 9V Dc 500 mA power source, the 500 ohm pot. and 100 ohm r2. Now where do I connect the led, what to measure and at what point etc. etc. in order to get the Vf and IF of a given LED.
Or there is some other better way out also ?
Thanks