Building a Car Power Management Device

Bringing Smart and Reliability Power to Your DIY Car Projects

Managing power can often pose a significant challenge for DIY enthusiasts looking to integrate IoT, infotainment, or other devices into their vehicles. We need to deal with electrical noise and protecting the battery from draining. To address these issues, we’ll develop and construct a smart power management device for the car. This innovative solution will prevent unnecessary drainage of the vehicle battery when the vehicle is not in operation. The device will also feature a programmable functionality allowing the device to remain operational for a predetermined amount of time. This capability can be invaluable during brief stops, such as refueling, eliminating the need for the device to restart unnecessarily.

At the heart of our smart power management system lies an Espressif ESP32. The ESP32 relies on several other devices to monitor the vehicle’s power state and control the main device’s power. By the end of this series, we will have created the power management system and configured a ROC-RK3328-CC single board computer (SBC) to power on and off and communicate with the ESP32, managing the power. Let’s take a closer look at the components we’ll need and the roles they’ll play:

1. ESP32 Controller: Serving as the device’s central nervous system, the ESP32 controller handles voltage monitoring, controlling power to the main device, and communication with other vehicle systems. The ESP32 can even be put into deep sleep mode for even more power savings. The ESP32’s Ultra-Low-Power (ULP) coprocessor can still monitor the vehicle power state while eliminating most of the power consumption.
   
2. ROC-RK3328-CC Module: This workhorse complements the ESP32 controller, providing additional computational muscle for advanced vehicle applications. With its high-performance architecture, the ROC-RK3328-CC module empowers the device to tackle complex tasks with ease, from data processing to system management. It can even run full-blown Linux.
   
3. Relay:
   The relay acts as a switch in the power supply circuit, allowing the ESP32 controller to safely control the power state of the ROC-RK3328-CC. When the ESP32 signals the relay to switch on, the relay’s contacts close, allowing current to flow to the ROC-RK3328-CC, thereby powering it up. Conversely, when the ESP32 signals the relay to switch off, the relay’s contacts open, cutting off the power supply to the ROC-RK3328-CC, effectively shutting it down.
4. Voltage Regulator: Tasked with converting the vehicle’s 12V power supply to a stable 5V output, the voltage regulator serves as the linchpin of the device’s power management system. With its precision control and efficiency, the voltage regulator ensures consistent and reliable power delivery to the ESP32 and ROC-RK3328-CC modules, even in the face of fluctuating input voltages.
   
5. Voltage Sensor: We will built a voltage sensor we can use to continuously monitors the vehicle’s electrical system. We’ll use it to detect changes in car’s main voltage levels and determine when the vehicle is running or idle in order to protect the battery integrity.
   
6. 20×4 LCD Display: The LCD display enables us to provide real-time feedback on system voltage system to determine battery and charging help. It could also use it to display vehicle status, power consumption, and diagnostic information. The LCD display enhances user interaction and can empower drivers with vital insights into their vehicle’s performance.

To illustrate the need for a smart power manager lets consider a car with a builtin streaming server using a ROC-RK3328-CC board. When the vehicle starts the ESP32 through the voltage sensor detects the higher voltage as the cars charging system engages. The ESP32 in turn triggers the relay closing the circuit to enable power to the ROC-RK3328-CC allowing it to boot up. When the trip is over the ESP32 again detects a voltage change as the charging system winds down. This time the ESP32 detects the voltage drop, as the car is now powered only by battery, so it signals to the ROC-RK3328 to power down via UART communication. Optionally we can have the ESP32 delay signalling the shutdown to the ROC-RK3328-CC for cases such as short stops to fill up with gas. In these cases it will allow occupants to continue using the service or make it available quicker.

In conclusion, for the DIY enthusiasts seeking to integrate IoT, infotainment, or other devices into their cars a smart power management system is essential. It addresses the need for a reliable clean power while protecting against unnecessary power drain.