Overview
The 74165 (typically 74HC165) is an 8-bit serial shift register that “loads” data from eight parallel inputs and shifts it out through a single serial output. It is the essential “Input Expansion” tool for makers. Instead of using 8 separate pins to read 8 buttons, you can use one 74165 to read them all using just 3 or 4 pins on your microcontroller. It’s the industry standard for building custom game controllers, MIDI keyboards, and large-scale sensor arrays.
Key Features
8-Bit Parallel Load: Samples all 8 inputs simultaneously with a single “Latch” command.
Complementary Outputs: Provides both the shifted data and its inverted version (Q and /Q).
Easy Daisy-Chaining: Connect multiple 74165 ICs in series to read 16, 32, or even 64 buttons using the same few pins on your Arduino.
Wide Compatibility: Works seamlessly with 3.3V and 5V systems (Arduino, ESP32, Raspberry Pi).
High Speed: Clock frequencies up to 50MHz, ensuring zero lag for user inputs.
Technical Specifications ⚙️
| Feature | Specification |
| Logic Family | 74HC (High-Speed CMOS) |
| Operating Voltage (VCC) | 2.0V to 6.0V |
| Number of Inputs | 8 Parallel Bits |
| Output Type | Serial (S-Out) |
| Package Type | DIP-16 (Breadboard & Socket Friendly) |
| Typical Quiescent Current | 80 muA |
| Operating Temperature | -40°C to 85°C |
The Perfect Partner
Think of the 74165 as the “Inbound” version of the 74595.
Use 74595: To turn 3 pins into 8 LED outputs.
Use 74165: To turn 3 pins into 8 Button inputs.
Together, they allow you to build massive control panels with almost no pins used on your main controller.
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