Let's assemble a completely analog PWM LED brightness controller using four operational amplifiers and figure out why PWM is needed and what it is.
LED fixtures need drivers to convert AC to DC, lower voltage, and stabilize current. Drivers can enable dimming. They can be 40–50% of fixture cost. While LEDs last up to 100,000 hours, drivers last ~50,000 due to aging capacitors. High-end drivers use film caps but cost more. Focus on driver warranty for a better gauge of overall fixture longevity.
Using a 74LS90 and resistor DAC, the circuit outputs stepped voltages for LED brightness. An op amp amplifies them, providing incremental LED current. Simple dividers and counters manage timing, while a flip-flop and 555 monostable enable manual or automatic stepping. This low-cost approach demonstrates basic LED dimming with minimal components.
A seemingly simple thing - an LED amplifier. The user chooses a device of suitable output power and uses it. But the devil lies in the details. From this post, you will know how LED strip amplifiers differ, what is not written in the documentation, where and in what lies, and what problems these devices can create. And also any buyer wants to understand why these simple devices have a large price range.
With Fresnel lenses focusing heat (IR) onto pyroelectric sensors, PIR sensors detect motion from changes in IR distribution. Two amplification stages and a window comparator boost signals, triggering a relay output. Chips like BISS0001 unify these elements, adding adjustable timing and re-trigger controls for seamless motion-detection functionality.
