This circuit is based on a very old application note from
exar, in this the frequency is fixed by IC1 and IC2 -P1
controls the duty cycle. you need to compute the R and C
values to get what you need, IC - LM555.
Even a Toy can be made with 555 -
Electronic Fifteen LED Roulette
You have to study the circuit and do something more
innovative perhaps, just copying is ok for learning but it
will get you nowhere, so learn and then innovate, the eagle
circuit is given below so you can learn by editing it, also
design a PCB with it, and you can even make a PCB at home to
learn, but it is always good to get PCBs done by a PCB vendor,
but you should understand his problems, then you will design
well, so make a few PCBs.
Here is my main 555 circuits stub at my Schematics blog -
555-Circuits - delabs Schematics
The photo Transistor conducts when light is falling on
it. When the beam is broken by an object the transistor
will turn off or go to high impedance. This takes the
comparative input high which turns Pin 3 Output Low, the load
could be a Relay Coil or Buzzer. Vcc could be 5V to 9V.
Relay Coil must be High Resistance Type, use protection diode.
Images above are from the Original Signetics 555 Datasheet
20th Apr 2020
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