Monitoring circuits in battery chargers, water-level indicators, etc use LEDs to indicate the status of certain conditions. Presented here is a multiple status indicator circuits that use a single RGB LED for seven different indications.
Circuit and work for Multiple Status Indicator Using Single RGB LED
A circuit diagram of the multiple status indicators using a single RGB LED is shown in Fig. 1. It is built around priority encoder CD4532 (IC1), common-cathode RGB LED (RGB1), and a few other components. IC CD4532 is an 8-to-3 priority encoder that converts 8-bit data inputs (D0 through D7) into 3-bit binary data (Q0 through Q2).
The RGB LED is connected to the binary output of IC1. For every high output (5V) of IC1 at data pins Q0 through Q2, the LED emits different colors for different data sequences as given in the table. Resistors R1 through R3 are used to limit the current flowing through the LED, one for each color. With a single RGB LED, up to seven different states can be indicated through different colors. The data sequence is given in the table.
Construction and testing
Features of CD4532 :-
- Converts from 1 of 8 to binary
- Provides cascading feature to handle any number of inputs
- Group select indicates one or more priority inputs
- Standardized, symmetrical output characteristics
- 100% tested for quiescent current at 20 V
- The maximum input current of 1 µA at 18 V over full package temperature range; 100 nA at 18 V and 25°C
- Noise margin (full package-temperature range):
0.5 V at VDD = 5 V
1.5 V at VDD = 10 V
1.5 V at VDD = 15 V - 5-V, 10-V, and 15-V parametric ratings
- Meets all requirements of JEDEC Tentative Standard No. 13B, “Standard Specifications for Description of ‘B’ Series CMOS Devices”
- Applications:
- Priority encoder
- Binary or BCD encoder (keyboard encoding)
- Floating point arithmetic
