Mutchus

The post explains a simple automatic mains lamp reverse dimmer circuit which can be used to imitate a sunrise effect. A sunrise simulator lamp is a modified version of a dimmer circuit. 120V AC lamp is connected to a bridge rectifier that supplies DC though there is no functional difference as the lamp is passive and being resistive in nature there is no operational problem. The circuit is made such that the lamp illuminates over a period of 20 minutes. The lamp is connected in series with a N channel MOSFET. Here in this case IRF 640 having a V -DS of 200V and I of 11Amp at 100oC or an IRF 740 having V-DS of 400V and Id of 6.3Amp at 100oC is recommended. However, for a 120V supply IRF 740 is a better choice. A current limiting resistance is employed in series with the lamp. The lamp has a drawing current of 500mA that determines the wattage of the current limiting resistance. LM324 a quad OP-Amp is employed for the multiple stages required to build the circuit. A triang...

In this circuit, a 120VAC lamp is slowly illuminated over a approximate 20 minute period. The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp. A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power. The bridge rectifier should be rated at 200 volts and 5 amps or more. In operation, a 700 Hz triangle waveform is generated at pin 1 of the LM324 and a slow rising voltage is obtained at pin 8. These two signals are compared at pins 12 and 13 to produce a varying duty cycle rectangular waveform at pin 14, which controls the MOSFET and brightness of the 60 watt lamp. Sunrise Lamp Circuit Diagram:  When power is applied, the lamp will start to illuminate within a minute or so, and will slowly brighten to full intensity in about 20 minutes. You can make that longer or shorter with adjustments to the 270K resistor at pin 9. The 2.2 ohm resistor and .015uF cap connected to the lamp serve to supress RFI. The diode at pin 9 and ...

I have a couple of front door LED lights which I would like to switch on automatically during the evening/night. The two conventional methods that are commonly available had their disadvantages: A timer switch is the easiest and cheapest solution, but doesn’t take into account day light savings. Besides that, in Einhoven, the Netherlands where I live in december the sun sets around 16:30 while in June it doesn’t get dark before 22:00. A simple timer doesn’t take that into account either. Since you only want the lights on when it gets dark, instead of time you can also use a light sensor to distinguish day and night. You have these front door lights that have this built in. The problem that I had with these devices is that they start bouncing (‘flickering’) around sunset/sunrise. They constantly turn on/off which causes damage to the LED lights I was using. This cost me already several expensive led lights. [ ]