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Thanks, I 've bought multimetr.
Can I change Buzzer 12V 30mA to 5V 30mA with a source 9V of resistor 135Ohms ?
But my main question is about fotoresistors : Can i buy fotoresistor which after break light beam have very small resisience ? All of fotoresistors in shops make it conversely
If the buzzer is rated 5V @ 30mA, then you can use it with a 9V supply by putting a 120 or 150 ohm resistor in line.
You can use a transistor to turn on the buzzer, in response to your photodetector going dark.
Can you make a schematic how to connect buzzer and transistor with photodetector ?
Why I need potentiometer ?
How intensivity I will have from this transformer, becouse max of colector in transistor is 100mA
And why in the base of transistor is a resistor 2,2k ?
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