The CENTRAL SEMICONDUCTOR 2N2906, 2N2907 series types are silicon 60V 600mA 400mW PNP epitaxial planar transistors designed for small signal, general purpose switching applications.
The BC547 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin.
The ESP32-S is a wireless module based on ESP32, supports Wi-Fi and Bluetooth 4.2, with built-in 32Mbit Flash, in the SMD38 package. There are also on board PCB antenna and metal shield.
The DS3231SN is a low-cost, extremely accurate I²C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping.
The CD4515BE is consist of a 4-bit strobed latch and a 4-to-16-line decoder. The latches hold the last input data presented prior to the strobe transition from 1 to 0. Inhibit control allows all outputs to be placed at 1 regardless of the state of the dat