I am just a hobbyist and I have a typical schematic I've always used to switch on/off relay coils.
This has always worked the last 3-4 times I've used it (without R1 and C1)
But this time, I can't turn the relay on at all (the transistor collector doesn't drop to GND (~200mV).
If I measure the collector voltage, it starts at 5V then after some seconds it drops to 3.5V-4.5V. I'm pretty sure the few times I've used this in the past (without R1 and C1, the base is connected to a GPIO pin instead) it managed to switch the relay on when transistor is on.
The only things I have changed (I think) is the introduction of R1 and C1 and Vcc 3V instead of just sending GPIO HIGH/LOW to the 1K base. I've also tried various values for R1 and C1 that I have with me.
I'd like to stop guessing what R1 and C1 values I should have. Ideally I would like the relay to switch 5-10 seconds after I connect R1 to Vcc. Currently, R1 & C1 are set to 100Kohm & 220uF to give about 5 seconds.
Note: Transistor is S9011 I think. Or 9013. Relay is an 8 pin 5V relay (2 for coil, 3 one side and 3 another side) - come to think of it, I've never used this kind of relay before - I've always used the 5 pin one, but this 8 pin one is the only one I have around this house. So this is also another thing has changed from my prior experience.
Thanks for reading.