Way to modify an AC dimmer into a light switch circuit, to turn ON-OFF and automatic light dimmer or two in one form. Since, the general dimmer uses a triac to control a load like a relay contact. So we can easily make it by a few parts.
See Figure 1.
We put the parts includes S2, LDR and RA-30K, 1/2W or RB to the AC dimmer circuit.
Turn-on a switch-S2, this circuit becomes the automatic light switch circuit.
When no light (or night) to LDR, the circuit will be closed,the lamp as load will glow.
And a potentiometer VR-500K adjusts the sensitivity.
This can control a outdoor or car park lamps to ON with itself and OFF in day. LDR1 a kind NTC is when the light hits it, then its resistance will decrease.
But in Figure 2 will work to reverse the first. Also choose the switch-S2 to LDR1 way, then this circuit becomes the automatic daylight dimmer switch circuit.
This can control lamps in the Warehouse, if open the door and have sunlight to LDR, will cause the lamp glow.
LDR1 in Figure 2 is PTC type. When the light strikes it. It will increase Resistance instead. This makes it possible control the on – off. Or appropriate to the dimmer light outside.
LDR may be installed on the box or outside. But the important need far from the light enough. It will be a circuit does not operate correctly.
We can soldered the more devices to the PCB and S1 may be install in box for safe when use.