transistors IR Emitter/Detector with 555 timer alarm

Posted on Feb 7, 2014

This circuit detects when a tube is empty and pulses a piezo buzzer in. 5 second intervals. I have it working with 5v on a breadboard, but I need to move it to 12v from a wall wart. Secondly, with 12v R1 should be 220 1W, but I want to stick with 1/4W resistors, maybe 510. Is that possible I realize that will bring down the 50ma current to QEE113 to 22mA, but my distance is only 1` so I think it will be enough

transistors IR Emitter/Detector with 555 timer alarm
Click here to download the full size of the above Circuit.

power. Thridly, I`m not sure how to calculate the size of resistors needed to go to the transistors. The values I have are from various samples I found on the net for 5v. Is there a formula that tells me what they need to be for 12v. I`m not able figure that out from the datasheets.

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