PAGE 058 OF 150 · WIRING LEDS
Wiring an LED Bar Graph
Bar graphs bundle several LEDs in one housing.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
What a bar graph is
An LED bar graph is a package of typically ten LEDs in a row. Each has its own anode and cathode connection, giving 20 pins.
Wiring
- Give every LED a resistor, such as 330 ohms at 5 V.
- Join all cathodes to ground, or use a driver to switch them.
- Check the pin 1 mark before inserting.
Driving
A microcontroller needs ten outputs, or a shift register can reduce that. Driver chips such as the LM3914 turn an analogue voltage into a dot or bar display.
REMEMBER
In series the same current flows through every LED.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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