Hi all
I have an old analog alarm system. I am hooking up the bell output to a microcontroller. Although the output voltage for the bell fluctuates around 6 to 9 volts. I need either a steady 0 or 5v for the input of the controller. I made a circuit with 2 2n222 transistor, acting as an inverting gate. The problem is that the spec sheet of these and most transistor have a Veb of 5 volt. my Ve is at ground therefor my Veb exceeds this. any ideas on how to get pass this issue. Thought about a voltage divider at the output of th bell , but I am scared that if voltage drops a bit below 6v, the inverter will not pick it up as positive voltage. thanks k