I'm doing a LED desk lamp, can be through the outside light intensity automatically adjust the brightness of LED, using PWM technology, how to do excuse me
LED lamp with a constant current source control, add a photoresistor adjust current source circuit; PWM control, it is not necessary to make it too complicated, say little and a few watts
With photosensitive components after sampling the operational amplifier amplification, then send the feedback signal input terminal of the PWM controller, light to adjust the sensitivity of the feedback signal strength by adjusting the op-amp magnification (resistance), no need for A/D converter and SCM, that is too complex, workload big cost is high. A photosensitive diode, an op-amp, a PWM controller (e.g., UC3843), plus a few resistance capacitance inductance, there are ten yuan or so.
Using PWM technology, you need to use single chip microcomputer output a certain duty cycle of square wave, the duty ratio, the greater the more bright. Also need to use sensors to collect light intensity, the establishment of a model, to achieve automatic brightness adjustment.
A photosensitive diode, followed by current - voltage conversion and amplifying circuit, and then sent to the AD converter, into a digital signal, for single chip microcomputer. Single-chip microcomputer according to the amplitude to send a PWM control signal to the pulse width control chip.
