Modern White LEDs: A Powerful Light Source
In today’s market, readily available white LED emit a substantial amount of light, to the extent that direct eye contact should be avoided due to their brightness. While these LEDs are currently on the expensive side, it’s anticipated that their cost will decrease in the future. With just a few of these high-intensity white LED, you can create an excellent solid-state pocket torch, showcasing the impressive capabilities of these light sources.
Efficient LED Illumination: Innovative Circuit Design
A straightforward approach involves utilizing a distinct series resistor for each LED, each operating at approximately 3.5 V with a current of 20 mA. However, depending on the supply voltage, significant power loss can occur within these resistors. The converter illustrated here provides a high enough voltage to enable the connection of ten LEDs in series. Moreover, this converter ensures a consistent current supply rather than a constant voltage.
Regulated Current Supply for Optimal LED Performance
Introducing a resistor in series with the LEDs results in a voltage drop contingent on the LED current. This voltage is compared to a 1.25 V reference value inside the IC, maintaining a steady current of 18.4 mA (1.25 V ÷ 68 Ω). The IC employed here belongs to National Semiconductor’s ‘simplnee switchers’ series. Notably, the inductor’s specific value is not crucial; it can fluctuate within a range of plus or minus 50 percent.
Optimal Components for Circuit Design
For the coil component, the black Newport coil with specifications of 220 µH at 3.5 A (1422435) stands out as a suitable choice. As for the diode, virtually any Schottky diode can be utilized, provided it can handle a minimum of 1 A at 50 V. Although not obligatory, Zener diodes are included in the circuit to safeguard the IC. This precaution becomes essential in case the LED chain is inadvertently interrupted during experiments, preventing the voltage from reaching levels that might jeopardize the IC. Unfortunately, the specific PCB featured in the illustration is not commercially available pre-made through the Publishers’ Readers Services.
Essential Electrical Component: The Resistor
A resistor, a passive two-terminal electrical component, serves as a fundamental circuit element by introducing electrical resistance. Within electronic circuits, resistors play various crucial roles, including reducing current flow, modifying signal levels, dividing voltages, biasing active elements, and terminating transmission lines, among other applications.
Counter-Intuitive Importance of Resistors
Despite the dissipation of energy due to resistance, resistors are indispensable for the smooth operation of electronics. Their primary function lies in preventing other components from receiving excessive voltage or electric current, ensuring the overall stability and functionality of electronic systems.