3DU33 Silicon NPN Phototransistor for Smoke Detector
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Prices updated: 12 Oct 2026
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About this product
Silicon NPN phototransistor used as the light-sensing element in optical smoke detectors. It converts incident light into collector current, and it is also useful in light-sensing and optical switching circuits in hobby and learning projects.
Specifications
- Device type
- Silicon NPN phototransistor
- Application
- Smoke detector (optical sensing)
Frequently asked questions
How do I wire the 3DU33 phototransistor in a basic circuit?
In a common-emitter arrangement, connect the emitter to ground and the collector to the supply through a load resistor. Take the output voltage at the collector, and leave the base open for light-only operation.
Can the 3DU33 output drive an Arduino input?
Yes. Read the collector voltage on a digital or analog input, and choose the load resistor so the output swings within the board's logic level. Set the threshold by testing under your light conditions.
