# RGB LED: 11.5V se 12.5V Supply, Resistor Value aur White

Sir ke points:

1. Supply 12V fixed nahi, **11.5V se 12.5V** (1V ka farq) tak badal sakti hai.
2. Resistor value **absolute max IF** aur datasheet limits ko dekh kar.
3. Red, Green, Blue **equal-looking brightness**, teeno saath on hon to **white**.
4. Agar mumkin ho to **ek hi resistor value**.

| Item | Detail |
| --- | --- |
| LED | NH-Z2727RGBA-SG (Foshan Nationstar) |
| Design | 4 LEDs series, 1 resistor per string |
| Supply | 11.5V se 12.5V |
| Use | Outdoor, USA, 70C ambient stress check |

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## 1. Datasheet limits jo use hue

| Item | Red | Green | Blue |
| --- | --- | --- | --- |
| Absolute max current (25C) | 25mA | 25mA | \~20mA (curve) |
| Max current at 70C (curve, andaze) | \~12.4mA | \~11.6mA | \~9.0mA |
| Design current (datasheet test current ke qareeb) | 12mA | 8mA | 5mA |
| Vf min / typ / max | 1.8 / 2.1 / 2.5V | 2.4 / 2.9 / 3.4V | 2.4 / 2.9 / 3.4V |
| Wavelength (typ) | 622nm | 530nm | 472nm |

- Vf sirf test current pr diya gaya hai (15 / 8 / 5mA).
- Sabse zyada current wala case: **12.5V supply + min Vf**. Resistor isi case ke hisab se chuna.

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## 2. Voltage range ka asar

Bacha hua voltage = Supply - (4 x Vf). Minus matlab LED on nahi hogi.

| Color | Supply | Min Vf | Typ Vf | Max Vf |
| --- | --- | --- | --- | --- |
| Red | 11.5V | +4.3V | +3.1V | +1.5V |
| Red | 12.5V | +5.3V | +4.1V | +2.5V |
| Green/Blue | 11.5V | +1.9V | **-0.1V** | **-2.1V** |
| Green/Blue | 12.5V | +2.9V | +0.9V | **-1.1V** |

- **Red** pr range ka asar kam hai.
- **Green/Blue:** 11.5V pr typical LED bhi on nahi hoti (4 x 2.9V = 11.6V). 1V ka farq inke liye bohat bara hai.

---

## 3. Har color ka safe resistor (absolute max + 70C limit ke andar)

| Color | Resistor | 12.5V, min Vf (sabse zyada) | 12V, typ Vf | 11.5V, typ Vf | 11.5V, max Vf |
| --- | --- | --- | --- | --- | --- |
| Red | **442 ohm** | 12.0mA | 8.1mA | 7.0mA | 3.4mA |
| Green | **365 ohm** | 7.9mA | \~1.1mA | on nahi | on nahi |
| Blue | **576 ohm** | 5.0mA | \~0.7mA | on nahi | on nahi |

- Teeno colors 12.5V + min Vf pr bhi absolute max (25mA, Blue \~20mA) aur 70C limit (12.4 / 11.6 / 9mA) ke andar hain.
- Typ wale currents fixed Vf se nikale hain. Asli LED mein current kam hone pr Vf girta hai, to G/B kuch mA zyada deti hain. Phir bhi **dim hain aur 11.5V pr band** ho sakti hain.
- Resistor: 1206, 0.25W.

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## 4. Kya ek hi resistor value chalegi?

12.5V, min Vf (sabse zyada) / 12V, typ Vf:

| Common value | Red | Green | Blue | Verdict |
| --- | --- | --- | --- | --- |
| 330 ohm | 16.1 / 10.9mA | 8.8 / 1.2mA | 8.8 / 1.2mA | Red 70C limit (12.4mA) se upar, **unsafe** |
| 442 ohm | 12.0 / 8.1mA | 6.6 / 0.9mA | 6.6 / 0.9mA | Safe, lekin Red \~8mA aur G/B \~1mA, **rang red/orange, white nahi** |

**Jawab: ek hi value nahi chalegi.** Red ko G/B se alag current chahiye, aur G/B ko 12V pr bohat kam voltage milta hai.

---

## 5. White ke liye brightness ka sach

- **Equal mcd white nahi dega.** Aankh Green ko zyada, Blue ko kam dekhti hai, aur teeno ki wavelength alag hai.
- Datasheet test currents (15 / 8 / 5mA) pr brightness 450 / 680 / 110 mcd hai. Ye ratio thora **pinkish** white deta hai.
- Neutral white (\~5000K) ke liye andaze:

| Item | Red | Green | Blue |
| --- | --- | --- | --- |
| Current ratio | \~11.4mA | \~8mA | \~3.6mA |
| Brightness (mcd) | \~360 | \~680 | \~87 |
| Brightness ratio (G = 1) | \~0.5 | 1 | \~0.13 |

- Ye numbers **andaze** hain (datasheet mein chromaticity nahi hai).

---

## 6. Best-effort white set (fixed resistor, 12V typical LED ke liye)

| Color | Resistor | 12.5V min Vf | 12V typ (curve se) | 11.5V typ |
| --- | --- | --- | --- | --- |
| Red | **680 ohm** | 7.8mA | \~5 se 6mA | \~5mA |
| Green | **301 ohm** | 9.6mA | \~3.9mA | \~1 se 2mA |
| Blue | **487 ohm** | 6.0mA | \~2.3mA | \~1mA |

Brightness ratio (G = 1, andaze):

| Case | Red : Green : Blue | Rang |
| --- | --- | --- |
| 12V, typical LED | \~0.55 : 1 : 0.15 | White ke qareeb |
| 12.5V, min Vf LED | \~0.3 : 1 : 0.16 | Greenish/cyan |
| 11.5V, typical LED | Red zyada, G/B kam | Pinkish/orange |

- Red ko jaan boojh kar kam kiya hai (680 ohm), taake dim G/B ke saath balance rahe.
- Teeno colors absolute max aur 70C limit ke andar hain.
- **Rang voltage aur LED ke Vf ke saath badlega**, kyunke G/B ka current Vf aur voltage pr bohat depend karta hai.

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## 7. Seedha jawab

| Sawal | Jawab |
| --- | --- |
| Absolute max ke andar safe resistor? | **Haan:** Red 442, Green 365, Blue 576 ohm (section 3) |
| Ek hi value teeno ke liye? | **Nahi** |
| Fixed resistor se stable white (11.5V se 12.5V)? | **Nahi.** Sirf approximate white (section 6), rang badlega |

**Stable white ke liye kuch badalna padega (koi ek):**

- G/B ko **3 series** karna (board change)
- Controller se **PWM / color calibration**
- **Constant current driver**
- Suggestion (abhi design mein nahi): 12V se 16V boost converter

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## 8. Dhyan rakhne wali baatein

- Sab brightness aur color numbers **andaze** hain, final prototype pr naapna hoga.
- Garmi mein Vf kitna girta hai, datasheet mein nahi, isliye 70C ka guaranteed current nahi nikal sakte.
- Dense array mein LED surface 55C se neeche rakhna hai.
- Segment aur 9/10 ke LEDs **same reel/bin** se lo. 9/10 ki values abhi pending hain.