UV LED circuit - how many and which resistor?

In summary, the conversation discusses designing an electrical circuit for a UV light rigging in a bottle holder for tonic water. The plan is to use three 360nm UV LEDs in parallel with a supply voltage of 10.5V. The question is whether to use one resistor for the entire circuit or three separate resistors. It is recommended to use three resistors for even lighting and the suggested resistance value is 360 ohms.
  • #1
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Many years having passed since I last looked at an electrical circuit, I been asked to design an electrical circuit at work.

We make tonic water, and the idea is to create a holder for bottles with a built-in UV light rigging. Due to the relative efficiency, robustness, cheapness etc, I am going to use LEDs. Due to the fluorescence of quinine, we expect this to create quite a cool effect in nightclubs and the like.

My plan is to set up three 360nm UV LEDs (Vf 3.4V, I=20mA) in parallel. My supply voltage will be 10.5V.

My question is, will I need one resistor for each LED, or just one bigger one for the entire circuit? The LEDs are identical. Also, what resistance will I require.

Any help much appreciated!
 
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  • #2
Using three resistors is better because the voltages of the three LEDs are not exactly equal. If you use only one resistor, the LEDs will draw different amounts of current and you will have uneven lighting.

As for the value, R = (10.5 - 3.4)/0.020 = 355 ohms. 360 ohms is the closest 5% value. You should use at least a 1/4 W resistor.
 

Related to UV LED circuit - how many and which resistor?

1. How do I determine the number of resistors needed in a UV LED circuit?

The number of resistors needed in a UV LED circuit depends on the number of LEDs used and the desired voltage and current. Each LED typically requires its own resistor to regulate the current flowing through it. Therefore, if you have multiple LEDs in your circuit, you will need multiple resistors.

2. How do I calculate the resistance value for a UV LED circuit?

The resistance value for a UV LED circuit can be calculated using Ohm's Law, which states that resistance (R) is equal to voltage (V) divided by current (I). For example, if you have a 12V power supply and an LED that requires 20mA, the resistance needed would be 600 ohms (12V / 0.02A = 600 ohms).

3. Can I use any type of resistor for a UV LED circuit?

Yes, you can use any type of resistor for a UV LED circuit as long as it meets the required resistance value and power rating. However, it is recommended to use a metal film resistor for better stability and accuracy.

4. Do I need to consider the wattage of the resistor in a UV LED circuit?

Yes, you need to consider the wattage of the resistor in a UV LED circuit to ensure it can handle the power dissipated. The wattage can be calculated using the formula P = I^2 x R, where P is power in watts, I is current in amps, and R is resistance in ohms.

5. How do I know if the resistor is getting too hot in a UV LED circuit?

You can use a multimeter to measure the voltage drop across the resistor. If the voltage drop is significantly lower than the rated voltage, it could indicate that the resistor is getting too hot and its resistance is decreasing. You can also use a thermal camera to check the temperature of the resistor. If it is too hot to touch, it may need to be replaced with a higher wattage resistor.

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