autodim - a pre-settable automatic dimmer

autodim elektor november 1984 11-28 Light dimmers are available in all sorts of different forms. This circuit, however, is unlike any we have seen before. Its most important feature is the fact that at the push of a button it starts to dim the light automatically. The time taken to dim completely is about thirty minutes. This makes it ideal for a child"s bedroom, where it can be used instead of a night-light. As you leave the room after putting the child to bed the button on the dimmer should be pressed. The dimming process is then so gradual that the child does not notice it and can sleep peacefully. NMI autodim A dedicated IC The heart of the circuit is the Plessey SL440. This IC is intended for applications in which a.c. power is varied by using phase control. Elsewhere in this issue we dedicate an "Applicator" to the SL440. For this reason we will only deal here with how the IC is used in the autodim. Moving straight to the circuit diagram, figure 1, we see that mains power is...