FOUR POSITION TOUCH DIMMER
Any electric light may be adjusted with this dimmer to very low, low, medium, and maximum, which in most cases will be sufficient.
The dimmer may also be used as an electronic on/off switch, in which case the mode select pin (7) must be connected to earth (pin 1).
Such a switch does not produce sparks and consequent noise
The LS7237 has all the necessary facilities to drive silicon-controlled rec-tifier (SCR) Trii. Resistor R2 and capacitor C4 filter a 50 Hz signal from the mains that serves to synchronize the on-chip phase locked loop.
Network R1, C2, and D2 provide the supply for the LS7237, while filter L1/C1 prevents excessive noise from reaching the mains supply. Different types of triac may be used, as long as these can provide the required current, and are suitable for operating voltages of not less than 400 V. For safety’s sake, no deviations from the stated voltage ratings of the various components should be tolerated. The two 4M7 resistors pro-vide ample safety for the user: under no circumstances should these be replaced by a single 10 MQ resistor! The complete circuit is small enough to be accommodated in the pattress or plaster box of a light switch.