Quote:
Originally Posted by DarrenSV650S
When I tested the green LED it was flashing (finding a signal) and the reading kept jumping up and down. When it found a signal it settled on 3.3V
Don't understand why it needs an inverter  |
The LED could have a permanent +3.3V on the anodes, and illuminated by grounding the cathode - this is a common way of driving LEDs from IC's.
Equally it could have a perminant earth, and illuminated by sending +3.3V. In this case the 555 timer chip cannot be triggered directly, but adding a simple transistor inverter would sort it out.
Either way would read the same from a meter.
I have just ordered the timer circuit, I'll experiment when it comes.