A Light-Emitting Diode (LED) is a semiconductor device fabricated from materials that emit light. LEDs are made of gallium arsenic (GaAs), gallium arsenide phosphide (GaAsP), or gallium phosphide (Ga). When aiming to make a good LED sign, just make sure that your circuit is functional and your LEDs are in good condition. If you have a functional electronic circuit, you can’t go wrong in making your LED sign work.
- Knowledge of the project. In making a good LED sign, you have to be familiarized with how it will be connected. There are two ways of LED connection, parallel and series connection. A parallel connection requires more current. If the rated current of each LED is 30mA in two parallel connections, the supply needed for the two LEDs should be 60mA. In series connection, it requires more voltage.
- Voltage supply. The supply voltage should be the sum of the rated voltage required for LED. If the rated voltage of each LED is 1.5 volts in two series connection, the supply needed for these LEDs is 3 volts.
- Common anode internal connection. To make the connections of a seven-segment LED used to display numeric character such as clocks, calculators and score boards, all positive of LED are tied together and connected to the positive terminal of the supply while all negative of the LED are connected to the a – g terminals. This kind of connection is called the common anode internal connection.
- Common cathode internal connection. All of the negative LEDs are tied together and connected to the negative terminal of the supply while the positive terminals are connected to the a – g terminals. The voltage used on a cathode should be at an appropriately lower voltage than the anode (about (0.7 V) to make the connection work in a common anode display. For a common cathode, anode voltage should be higher than cathode node by about 0.7 V to make the connection functional.
LEDs are available in different colors, sizes and shapes. The most common of LED colors are Infrared (IR) – GaAs which is invisible, Red/Yellow – GaAsP which is visible, and for Red/Green: GaP, which is visible. Blue and white are also available but they are more expensive. Red is the most common and the price is cheaper. For the shape of the lights, rectangular shapes are readily available and are most effective for illuminating a legend by directly backlighting a transparent character so that it will stand out.
Hermetic LED is sealed with a coating of silicin gel and a hermetic glass-to-metal seal. Tri-color LED is made from two different colored LEDs connected in reverse polarity, parallel to each other and in a single package. The dual-color LED has two separate anodes and a common cathode. This is ideal for an active visual indication of binary electronic states. The flasher LED has a built-in IC chip in its structure. The chip acts as a timer so that the current pulser works through the LED, causing the light to flash three times per second. Following these tips will teach one how to make good LED signs.