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...

A lamp dimmer circuit can be conceived in so many ways but the challenge is cost effectiveness and reliability. Thyristors (or SCRs) and TRIACs are the major components associated with the lamp dimmer circuit. Direct on line ( 120 VAC ) dimmers can be configured either by two TRIACs connected anti parallel or it can be configured by 4 number of SCRs in the same topology for a full wave phase control. But this is a costly methodology. The full wave phase control topology, as shown in the circuit was found in a RCA (Radio Corporation of America) power circuit book,1969. In fact, so far as power circuit is concerned, this is one of the cheapest effective typologies. A full wave rectifier bridge is being employed in series with the AC line along with a SCR, the rectified AC also had its zero crossing. The frequency of which is double that of the supply line and hence commutation of SCR at its natural zero is possible. Apparently it may appear that the SCR is working on a DC l...