What is the significance of using a Sonalert over a different type of buzzer

A Sonalert (brand name) is a solid state buzzer. The significants in my circuit, as some already said, is that an electromechanical "buzzer" open-circuits once every oscillation and would stop the SCR from conducting. That's why you would need a resistor across it, to maintain a conductive path. A solid state buzzer conducts continuously, so wouldn't need a parallel conductive path.

In your simulation of my circuit, the resistor simulating the Sonalert should be in the 500 to 1K range. 100K would not allow enough current to maintain conduction in the SCR. For an electromechanical buzzer it would be in the 100 to 500Ω range. And simulated by a relay with its coil powered through its C and NC contacts. Why did you pick 1.0uF for C1 and 100K for R1? R1/C1 are only to provide a brief pulse to turn on the SCR. The values in my schematic were "bench tested" and worked. Oh, and the alarm continues until you lift your finger off the reset switch.

any ideas on swapping the relays out for something solid state?

There are hundreds of ways to do it with solid state circuits, but I don't think you will find one with a smaller parts-count/size than mine (actually, mvs samara's). Since your original post said "remote" you might want to add a resistor and LED across the alarm line to indicate that there still is an alarm, when the audible indicator is silenced.

Ken

Originally Posted by KMoffett

A Sonalert (brand name) is a solid state buzzer. The significants in my circuit, as some already said, is that an electromechanical "buzzer" open-circuits once every oscillation and would stop the SCR from conducting. That's why you would need a resistor across it, to maintain a conductive path. A solid state buzzer conducts continuously, so wouldn't need a parallel conductive path.

In your simulation of my circuit, the resistor simulating the Sonalert should be in the 500 to 1K range. 100K would not allow enough current to maintain conduction in the SCR. For an electromechanical buzzer it would be in the 100 to 500Ω range. And simulated by a relay with its coil powered through its C and NC contacts. Why did you pick 1.0uF for C1 and 100K for R1? R1/C1 are only to provide a brief pulse to turn on the SCR. The values in my schematic were "bench tested" and worked. Oh, and the alarm continues until you lift your finger off the reset switch.

There are hundreds of ways to do it with solid state circuits, but I don't think you will find one with a smaller parts-count/size than mine (actually, mvs samara's). Since your original post said "remote" you might want to add a resistor and LED across the alarm line to indicate that there still is an alarm, when the audible indicator is silenced.

Ken

I will redo the sonalert simulation with the values you suggest. The resistor substitution may be the reason why the circuit does not appear to be working correctly.

I like the LED idea. Thanks.

I'm old-school. I don't have simulation software, so I "usually" try to do the real thing.

Ken

Originally Posted by ADWSystems

I resimulated the circuit with 1k for the buzzer instead of 100K. It works very nicely. Now to dig up an SCR.

I choose the 1uF and 100K values because with the 100K resistor substituted for the buzzer the circuit wasn't working. I didn't know that a) the circuit was bench tested, and b) the required resistance to substitute for the sonalert; which turns out was too high to make the circuit work. In short I butchered your bench testing because my sonalert-resistor substitution was too high in the simulation.

any small SCR would do , even in a TO92 package.