Sub

Main

Please ignore the left side of the bottom schematic.
I have both these buzzer schematics in two other threads but I think this might more exposure as it applies to other than buzzers. Thank God.
I am going to call them
Sub and Main.
I struggled with this quite a bit as to how do I wire something like this ? Where some of the connections are to a resisted Sub ground whereas Main is to, hmmm, (whole unresisted ground ? )
I don't know how to phrase it except that the sub schematic seemed to be getting part of something rather than the "whole" something, whatever something is. Volts, amps, another, ?,.
What I wound up doing was to substitute the Sub schematic in place of the Main buzzer.

For the Main schematic I didnt know what to do with the connections that went to V-. Was it to the same as the Sub V- ?
It doesn't seem kosher that there can be 2, V minuses. I made only one and both Main and Sub connected to it and God help me it worked !
In the Sub schematic, where the G connects to V-, that looks to be different than where in the Main schematic, the emitter of PN2222 connects to V-
Maybe it makes no difference and I should retire.

Apologies if this makes no sense at all.

George KG5TKY

 

In the Sub schematic, where the G connects to V-

It doesn't. G connects to one end of the 1k resistor. The other end of that resistor connects to -V (i.e the battery negative terminal).

 

It doesn't. G connects to one end of the 1k resistor. The other end of that resistor connects to -V (i.e the battery negative terminal).

Thank you Alex, but I got that. My question concerns the connection of the emitter of pn2222. Is it the same place as G ?

 

You need 2 transistors in this circuit…one to make the buzzer buzz, and the other to drive the buzzer circuit with the photo diode.

Yes the 222 emitter goes directly to ground and the other grounds thru the 1k resistor.


But when I look at that circuit I can see some problems with simply placing the sub circuit in place of the buzzer.

Because it looks like the sub circuit needs to get positive directly.


You could probably get rid of the 1k in the sub and just let the one in the main control the current…but don’t quote me on that…

 

Maybe after I learn a lot more I will be able to figure out how to marry 2 circuits. It will take me learning more about what the heck the resistors are for. In my simplicity they are for protection.
Then again in this case, as you suggested, the 1k on the sub might be able to be eliminated and use the other.
It is it's position on the V- line that I have no clue as to understanding.
I really need to get back to basics.
Plus my understanding of V- ( ground ?). To me it's where you dump all the volts or amps you don't need.

Thanks again