See photo #1, when plenty of light shines on the photocell, resistance is 12 Ω, the relay does not respond. In photo #2 the photocell is removed and the relay responds as expected. I can add a transistor and make this circuit work but my question is, why this doesn't work as indicated in photo "1?
Obviously the coil in the relay has some effect.
Information edited in from comments:
- The relay is an SRD-05VDC-SL-C from Songle Relay.
- Its coil voltage is 5 V.
- The photocell is about 12 Ω when fully illuminated.
- The supply voltage is 5 V.
- The circuit works fine if the photocell is replaced by a 15 Ω resistor.