MyOldPCS

In one of my projects, I needed a protection module to prevent a lead-acid battery from over-discharging. I picked up the first module I could find. The module is built around the LM358 operational amplifier. The intended purpose of this module is simple: when the battery voltage reaches a critically low level, it should disconnect the load to prevent further discharge until the battery is recharged. The cutoff threshold is adjustable; for old 7Ah batteries, I usually set it to 11.0V - 10.95V, though for today’s tests, I set it to 10.5V. During testing, I discovered a significant “nuance.” The idle current consumption of the module with a “charged battery” is 7mA, which is perfectly fine. However, what happens next is quite interesting. Once the voltage drops below the critical level, the relay clicks—and the current consumption jumps to 33mA. The Problem: Instead of energizing the relay when the battery is healthy, the circuit does the opposite. When the battery is already ...

For one of my recent experiments, I needed to investigate how much the Linux operating system actually impacts hardware performance. To do this, I had to test the same algorithm in two different environments: under Linux control and in bare-metal mode (without an OS). Beyond the data, I was driven by pure curiosity—it was fascinating to compare programming for microcontrollers versus “grown-up” 64-bit multi-core processors. For these tests, I chose the Allwinner H618 SoC: Ubiquity and Accessibility : It’s incredibly easy to find. My home embedded lab has about a dozen devices powered by this chip, ranging from TV boxes to various SBCs (Orange Pi, Walnut Pi, etc.). Back in the summer of 2025, H618-based boards could be snatched up for $15-$20, though prices have noticeably climbed since then. The Power-Periphery Balance : With four Cortex-A53 cores, you can hardly call this processor “sluggish.” It’s snappy enough for serious tasks. Working with UART, SPI, I2C, or timers here is st...