Red green dual color, red yellow green dual color LED beads: How to distinguish between yin and yang? Selection and Wiring Guide
The most classic requirement for dual color LED beads is that the device needs one light to display both operating and fault states. However, the rework rate for the procurement of dual color LED beads is surprisingly high, mainly due to three reasons: purchasing the wrong product for both yin and yang, mixing up two or three feet, and a significant difference in brightness between the two colors.
This article explains the structure, selection, and wiring of dual color LED beads in one go.
1、 Three structures, please take your seat first
1. Two feet dual color (reverse parallel)
The red and green chips are connected in reverse to two pins: when powered forward, they light up red, and when powered reverse, they light up green. The advantage is that it only occupies one lamp position with two solder pads, while the disadvantage is that it has two colorsCannot light up simultaneouslyAnd the driving circuit needs to be able to reverse direction (H-bridge or dual IO push-pull).
2. Three legged dual color (co yin/co yang)
The middle foot is the common terminal, with one chip controlled on each side. Two colors can be lit independently or simultaneously to create a third color (red+green=yellow). This is the most commonly used structure for industrial control panels.
3. Red, yellow, and green light beads
One LED bead integrates two chips of red and yellow green (or three chips of red/yellow/green with four pins), directly meeting the "stop standby run" three color logic. It is commonly used for charging stations, energy storage cabinets, and traffic indicators, saving space and installation compared to three single lights arranged side by side.
2、 Co yin or co yang? 30 second judgment method
- Co negative (co negative)Connect the common pin to GND and light up the other two pins with a high level. Compatible with NPN low side driver and single-chip IO direct push.
- Gongyang (Gongzheng)Connect the common foot to VCC and pull down the other two feet to light up. Compatible with PNP high edge drivers.
Buying the wrong resultThe entire batch of lights does not light up or only slightly lights up when connected. Before placing an order, be sure to confirm whether your driver circuit is on the high or low side. If the circuit has been finalized, buy the lamp directly according to the circuit; If it has not been finalized yet, it is recommended to choose common negative - single-chip direct push is the simplest.
Quick verification of incoming materials: The multimeter diode is set, with the red probe connected to the common pin and the black probe connected to both sides - both conducting (voltage drop 1.8-3.2V)common anodeThe reverse connection leads to conductivitycommon cathode.
3、 The most easily overlooked pitfall: two-color brightness matching
There is a natural problem with the red green dual color LED chips: the light efficiency and voltage of green (especially pure green 520-525nm) chips differ greatly from red light. The dual color light beads that do not perform sorting matching have a "red bright green dark" appearance when lit up, and the appearance is very poor when switching states.
When purchasing, it is recommended to directly make three requirements to the manufacturer:
1. Two color brightness grading matchingPaired packaging of red and green chip brightness levels within the same LED bead, consistent between batches
2. Provide IV classification data for each of the two colors, rather than just giving a 'comprehensive brightness'
3. Confirm voltage differenceLow voltage red (1.8-2.2V) paired with high voltage pure green (2.8-3.4V) dual color LED beads, the two current limiting resistors should be calculated separately and cannot share one
Our Hongcheng Optoelectronics' red green dual color and red yellow green dual color series are all sorted and shipped according to the matching brightness of two colors. There are two standard products for 0603/0805/1206 patch and 3mm/5mm straight insertion: common cathode and common anode.
4、 Copy homework according to the scene
| Application Scenarios | Recommended Solution |
|---|---|
| Power/fault binary indication, IO resources are tight | Two colored feet, red and green |
| Run/standby/fault three states, MCU direct push | Three legs sharing yin, red and green dual colors, red+green mixed with yellow to form the third state |
| Charging station and energy storage cabinet status lights | Red, yellow, and green dual color (red+yellow green) integrated LED beads |
| Multiple lights are arranged side by side on the panel, and color recognition is required when the lights are turned off | Colored colloid dual color version |
| Outdoor, long-range visibility | 5mm transparent colloidal spotlight design |
| Close viewing of the operation panel | Foggy colloid large angle version |
5 FAQ
Q: Can dual color light beads be used as two single color lights?
The three legged co yin/co yang version is completely acceptable, only one of them is needed; The two foot reverse parallel version is not suitable.
Q: What color is red and green when lit simultaneously?
The visual color mixture is yellow (red+green). Note that it is' looking yellow ', the spectrum is not true yellow light, and in situations where color is strictly required, it is recommended to use yellow light as a single color directly.
Q: Is the light decay of dual color LED beads synchronized?
Incomplete synchronization. Green chips (especially pure green) decay slightly faster at high temperatures. For long-term monochromatic lighting scenarios, it is recommended to choose low light decay packaging and control the driving current to not exceed 20mA.
6、 Summary
Remember four sentences when selecting dual color LED beads:First determine the structure (two legs/three legs/three colors), then determine the polarity (co negative/co positive), the brightness should match, and the voltage should be calculated separately.
Hongcheng Optoelectronics' red green dual color and red yellow green dual color series support free sample testing (with a minimum of 50 pieces for both positive and negative), and special wavelengths, brightness levels, and colloidal colors can be customized. Contact information: 139 2571 4318 (same WeChat account), sales@led-hc.com .
