Mike,
Here you go, thanks in advance.

I originally had a LED/resistor between the two for testing. When the 555 pulses the base of the resistor, the circuit is open, which is what causes the NC alarm zone to "alarm."

Tom

First, the attached -1 .asc file is what it takes to make the simulation run: As drawn; you had the entire circuit "floating", with no reference to Gnd. The voltage source driving the switch doesn't count.

Second, your drawing style sucks. the attached -2 .asc file is the circuit redrawn in such a way that I can understand it: supply rail on top, grounds facing down, power supply and inputs on the left, outputs on the right. Most current flow from top to bottom.

I also labelled some nodes so I can see what they are in the plots. I eliminated some unnecessary components.

The "short" through the transistor is not as bad as I initially thought because the base current is starved by the 10K base resistor.

 

Mike,
Thanks very much, it's nice to have my first Spice simulation running. I appreciate the lesson on circuit drawing, still learning.

FYI, last night I removed the smoothing capacitor (C3) since I felt it was overkill and also removed R1 (which I see you removed as well) which seemed redundant with R5 (on the switch side at least) and the circuit continued to perform as desired. I will remove the resistor to the reset per your drawing and retest today. Also you said the base is "starved" do I need a different value for that resistor?

I don't understand why you removed the diode? Since the switch is attached to the doorbell controller, don't I need to block the current from the controller to protect my circuit (post 25 shows this conceptually)?


Regards,

Tom

 

All, as promised, final pics and circuit. Installed it yesterday and it worked like a charm, got nearly instant text of person at door upon doorbell push. I need to neaten up the cables, but otherwise a completed working project. Please note that the soldered up circuit board has duplicate circuits as I have both a front and back doorbell and each one is independently controlled.

Next project - multiple water leak sensors for the alarm panel, hopefully I can design and implement these without being such a pest!

Again thanks to all who helped, particularly MikeML!

Regards,

Tom

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