This is lesson 5 here.
https://electrojets.blogspot.com/p/the-objective-of-this-project-is-to.html
It's the circuit on the right.
I am trying to figure it out by measuring various stuff and so far this what I have measured.
Also, the buzzer is not the one called out as I had one in my drawer. I tested it by putting from 1.3 - 9v dc onto it and it howls. I will post the datasheets at the end if that is proper.
Anyhow here are the readings under power.
VC with light = 1.9
VC dim light = 9
Current to the base ( is that IB? ), with light = 26.9 ua
dim light = 2.4 ua
Voltage drop at the buzzer 1.4 - 3.2

I can't figure out why it won't buzz. Voltage is high enough, so is it the current ? It seems like it is sensing the light and adjusting things. An interesting aside was that when I used an LED flashlight on the photo sensor, it had no effect. Different wave form I guess.

Thanks
George KG5TKY

 

First reaction - not enough current to the buzzer, perhaps. Does the buzzer work when you have a 1k resistor in series with it?
You don't say what photodiode you are using. If IR then as a visible LED won't have much IR output it won't (greatly) affect it. Some LEDs do generate IR however, unintentionally, but won't be much if the LED is efficient.
Simplest fix would be to use another transistor as an emitter follower between the 1k and buzzer.

 

Put the buzzer in the position of the 1K resistor, and ditch the 1K.

 

Hello,

What buzzer are you using?
Is it the same as in your other thread?
How to make this buzzer buzz ?

That one needs a circuit to buzz.

Bertus

 

It will give proper buzzing only if you put a coil in parallel with the buzzer. The coil and the capacitance of the piezo have to be tuned to the resonance frequency of the buzzer.

 

My other thread about the buzzer is finally working thanks to the fine folks here. The datasheet for the buzzer had a small schematic for the buzzer driver and that did it.
Of course it caused me another question that was too lengthy to repeat.
Basically, how to handle ground?, the---- of the battery, on a sub circuit of A main circuit when they are wired differently.
I am forever in your debt