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95445

Waterwheel Clock

This is a microcontroller based on the ESP8226 that controls a stepper motor to achieve mechanical operation.

1. Design Background
In this age of information overload, we often forget the wisdom of the ancients and the beauty of mechanics. However, the background of designing the waterwheel clock reminds us that even in the age of modern technology, we can combine traditional timekeeping methods with network time to create a unique and creative clock ornament. The
ancient waterwheel clock once used the power of water flow to measure time, showcasing humanity's keen observation and creativity in nature. Today, we can synchronize this ancient mechanism with network time and integrate it into modern mechanical design. Through precise calibration with network time, we can create a clock ornament that perfectly achieves time measurement, not only possessing practical functionality but also serving as a work of art, beautifying our living spaces.
This design is not only a tribute to ancient wisdom but also an innovative application of modern technology. It blends tradition and modernity, presenting a unique aesthetic and a spirit of the times. In this design, we can see respect for time and the inheritance of history, while also reflecting humanity's continuous pursuit and exploration of creativity.
2. Requirements Analysis

Network Time Synchronization: Utilizing the ESP-12F module to connect to the network and obtain accurate network time. This ensures the clock ornament always displays the accurate time without manual adjustment. Colored lights create a romantic atmosphere.
Colored light effect: Colored lights are arranged around the clock ornament. By controlling the color and brightness of the lights, a romantic and warm atmosphere is created, making the clock ornament not only a practical item but also a decorative piece.
Stepper motor control: The clock's timekeeping function is achieved by controlling the stepper motor to rotate at a fixed angle according to a certain number of teeth. The speed and rotation angle of the stepper motor can be adjusted as needed to make the clock ornament's timekeeping more accurate and smooth.
Battery life and charging function: The clock ornament is designed with a certain battery life, allowing it to work continuously for a period of time. It is also equipped with a charging function, which can charge the clock ornament via USB interface or other charging methods to ensure its stable operation over a long period of time.

3. Scheme Design
 
3.1 In this design, the hardware system includes an ESP-12F module microcontroller minimum system, a serial port download interface, a stepper motor, and a TP4056 charger.
Figure 3.1 Hardware System Structure Diagram
3.2 Minimum System of
the ESP-12F Module The minimum system of the ESP-12F module refers to the necessary components for the microcontroller to function properly and perform its functions. It generally includes four parts: power supply circuit, clock circuit, reset circuit, and download/debugging circuit. This design uses the LQFP144-pin main control chip, and some peripheral circuits are shown in Figure 3.2.
Figure 3.2 Pin Assignment Diagram of the ESP-12F Module
Figure 3.3 Physical Diagram of the ESP-12F Module
3.3 BOOST Boost Circuit
This circuit boosts the battery voltage to approximately 4.86V to prevent system malfunction when the battery power decreases. The chip used is the MT3608, a very common DC-DC power supply chip.
Figure 3.4 BOOST Boost Circuit Diagram
Figure 3.5 Physical Diagram of MT3608
3.4 Reverse Connection Protection and One-Button Power On/Off Circuit
When the battery and USB are powered simultaneously, there will be a short circuit due to overcurrent. This design uses D1 and Q3 to form a reverse connection protection circuit, allowing the USB port to charge the battery while simultaneously powering the system. Q1 and Q5 form a one-button power-on/off circuit. After power-on, the input power Vin charges capacitor C6 to the power supply voltage via resistors R5 and R11. MOSFETs Q1 and Q5 are cut off, and Vout has no output. Power-on state: When the circuit needs to be powered on, pressing switch S1 applies voltage to the gate of the NMOS transistor C1, causing Q5 to quickly saturate and conduct. The gate potential of Q1 is pulled down to near 0V, and Q1 also quickly conducts and saturates, resulting in a voltage output Vout. At this time, Vout, through resistor R2, is applied to the gate of NMOS transistor Q5, maintaining Q5's conduction and forming a self-locking loop. If S1 is not released, Vout will continue to charge capacitor C6, not affecting the power-on state of the circuit. If S1 is released, capacitor C1 discharges to near 0V through resistor R11 and the drain-sink of Q2, preparing the circuit for power-off. When the circuit needs to be powered off, press switch S1 again. Due to the effect of capacitor C6, the gate potential of NMOS transistor Q2 is pulled low to a low level, and Q5 is cut off. After Q5 is cut off, the gate potential of PMOS transistor rises to a high level, Q1 is cut off, and Vout has no output. At this time, switch S1 should be released, and capacitor C6 will slowly charge through resistors R5 and R11 to close to the input power supply voltage. It returns to the initial power-on state.
Figure 3.6 Anti-reverse connection and one-button power-on circuit diagram
3.5, Charging circuit
TP4056 is a high-performance single-cell lithium-ion battery constant current/constant voltage linear charger. The TP4056 uses an ESOP8 package and has fewer external components, making it very suitable for portable products and suitable for powering USB power and adapter power.
Based on the special internal MOSFET architecture and anti-reverse charging circuit, the TP4056 does not require an external sense resistor and isolation diode. When the external ambient temperature is too high or in high-power applications, thermal feedback can adjust the charging current to reduce the chip temperature. The charging voltage is fixed at 4.2V, while the charging current can be externally set via a resistor. When the charging current drops to 1/10 of the set value after reaching the final float voltage, the chip terminates the charging cycle.
Figure 3.7 shows the charging circuit diagram.
3.6. Stepper Motor Drive Circuit:
The ULN2003 is a high-voltage, high-current Darlington array composed of seven silicon NPN Darlington transistors. The circuit features are as follows: Each pair of Darlington transistors in the ULN2003 is connected in series with a 2.7K base resistor. At a 5V operating voltage, it can be directly connected to TTL and CMOS circuits, directly processing data that previously required standard logic buffers.
　　The ULN2003 is a high-voltage, high-current Darlington transistor array series, featuring high current gain, high operating voltage, wide temperature range, and strong load-carrying capacity, making it suitable for various systems requiring high-speed, high-power drives.
Figure 3.8 Stepper Motor Drive Circuit
3.7 Automatic Download/Debugging Circuit
In this design, the download interface has a reserved 2*10P horn-shaped connector, which can be used with Jlik, DAP, STlink downloaders or for debugging the microcontroller.
Figure 3.9 Automatic Download/Debugging Circuit Diagram
ESP Series Microcontroller Download Selection
The ESP32 has two startup modes: SPI startup mode (normal startup) and download startup mode. To achieve automatic program download, it is necessary to automatically enter the download startup mode upon power-up. The method is to pull GPIO0 and GPIO2 low simultaneously. Since GPIO2 is pulled down by default upon power-up (IO2 may be used as an SD card or for other purposes, so if a device is connected and the pin is high, download will fail), we can consider only GPIO0. Simultaneously controlling the reset pin (EN) will achieve automatic program download, as follows:
When EN rises from low to high (rising edge), the CPU resets. After reset, if GPIO0 is detected to be low, the CPU automatically enters the download startup mode!
3.8 WS2812REB Color Light Driver Circuit
The WS2812B is an intelligent externally controlled LED light source integrating control and light-emitting circuits. Its appearance is identical to a 5050 LED, with each element representing a pixel. Internally, each pixel includes an intelligent digital interface data latch, signal shaping, amplification, and drive circuit, as well as a high-precision internal oscillator and a 12V high-voltage programmable constant current control section, effectively ensuring high color consistency of the pixel light. The data protocol uses a single-wire return-to-zero (RZ) communication method. After power-on reset, the pixel receives data from the controller via the DIN pin. The first 24 bits of data are extracted by the first pixel and sent to its internal data latch. The remaining data is shaped and amplified by the internal shaping circuit and then forwarded to the next cascaded pixel via the DO port. The signal decreases by 24 bits with each pixel. The pixel employs automatic shaping and forwarding technology, meaning the number of cascaded pixels is not limited by signal transmission speed, but only by the required signal transmission rate.
Figure 3.10 S2812REB LED Driver Circuit
. 3.9 Night Detection Circuit:
Night detection is achieved by using a photoresistor and a resistor to divide the voltage.
Figure 3.11 3.4 Night Detection Circuit . Figure
3.10 Physical appearance
model is from T-site: https://www.thingiverse.com/thing:6285769