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Add buzzer to this circuit

hobbyelectronics

May 27, 2023
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I have already made this project and want to add a buzzer. It is a 'remote' light - now using 12volt power but works a bit too brightly with 16 v. Suggestions appreciated
 

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kellys_eye

Jun 25, 2010
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Chose a suitable buzzer (seems like the power rail is 15V so something aorund that operating voltage will do - you can use a 12V version with a dropper resistor but you'll probably get away with straight connection to 15V in this case).

Connect the '+' side of the buzzer to the +15V rail (top line) and the other side of the buzzer to one of the spare (Q5-Q8) outputs of the driver IC. When the appropriate output is selected - and I'm assuming the remainder of the circuitry allows selection past Q4??) then the buzzer will sound.

You can connect the buzzer to 'any' Q output and it will annoy the h*ll out of everyone whilst the lights are on.
 

hobbyelectronics

May 27, 2023
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Not sure what you mean by "spare", since every output pin is used. I really appreciate your comment, and
possibly a bit of an explanation for this project. It is a remote light, triggered by a small scoring box for sport fencing. No more than 96 Leds can be lighted at the same time and each array can be triggered independently by the scoring box. The output from the scoring box is 5volts and that allows the ULN 2803a to trigger the appropriate array/s. Could the buzzer be connected only to the red and green arrays, using their pins? This is the "negative" side of the circuit (of course) and I am assuming that this is what you mean by "connecting to any output pin" ( as I'd like the buzzer to sound when a red or green array is triggered) The arrays do not stay on very long at all.
 

kellys_eye

Jun 25, 2010
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Not sure what you mean by "spare", since every output pin is used.
OK, I assumed there were spare lines according to the 'incomplete' schematic but either way, connecting your buzzer across any of the outputs will make it sound.
 

hobbyelectronics

May 27, 2023
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OK, I assumed there were spare lines according to the 'incomplete' schematic but either way, connecting your buzzer across any of the outputs will make it sound.
Thank you! This is the one I made without a buzzer.
 

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