A follow-up to my earlier post Why is the output from this astable 555 the reverse of it's simulation?
The 555 output drives a 2N2222. The 2222 emitter-follower with a 4.7 kΩ resistance to ground, in it's turn, attempts to drive a PCB mountable relay (I meant to drive a 3055 and then the relay but decided to try to drive the relay directly before including the 3055). To determine whether the relay is triggered an analogue multimeter (resistance) has it's leads applied to the contacts on the relay.
This is curiosity rather than a problem; when the 555 output goes high the relay makes a lot of noise, and the NC opens over around 10 seconds from 0 Ω resistance to around 1 kΩ slowing as it increases (some kind of logarithmic rise).
- VCC = 12 V
- Rb at 2N2222 = 330 Ω
- Re at 2N2222 = 4.7 kΩ
EDIT: The relay JQC-3FC is connected at the take-off above R3 with the other end of the relay going to ground.
Applying 12 V to the relay directly switches the contacts instantaneously. Why the gradual opening through the timer circuit?