FAQ
TL;DR: Use a comparator to square the mains sample, then time edge-to-edge with your MCU; Arduino Uno’s 16 MHz clock limits resolution, and “Any load change on a generator driven power system will cause a frequency change.” [Elektroda, Anonymous, post #21683813]
Why it matters:** This FAQ helps students and hobbyists build and simulate a safe, Arduino-based grid‑frequency monitor for demand‑side control.
Quick Facts
- Arduino Uno clock: 16 MHz; interrupt latency and clock drift impact accuracy and timing. [Elektroda, Anonymous, post #21683811]
- Simple method: comparator → square wave; measure period via edge timing or count edges in a gate window. [Elektroda, Anonymous, post #21683809]
- Isolation is essential: use a sensing transformer and relay or isolated driver for breakers. [Elektroda, Anonymous, post #21683818]
- More headroom: Teensy/Raspberry Pi/Beaglebone increase timing resolution and enable data capture. [Elektroda, Anonymous, post #21683816]
- Small load steps shift frequency slightly; effects grow only with large system‑relative changes. [Elektroda, Anonymous, post #21683813]
How do I measure grid frequency with an Arduino?
Condition the mains sample safely, feed it to a comparator to create a clean square wave, and use the MCU timer to measure time between rising (or falling) edges. Convert period to frequency or count edges in a fixed time window. This approach is simple, fast, and works across wide frequency ranges if your timing resolution is adequate. [Elektroda, Anonymous, post #21683809]
What accuracy and speed can I expect from an Arduino Uno?
The 16 MHz clock sets base resolution (one tick ≈ 62.5 ns), but real accuracy depends on interrupt latency and the Uno’s clock drift. For relative changes, it works well; for absolute frequency, add calibration or a better timebase. “You’re going to need an accurate time source and/or calibration.” [Elektroda, Anonymous, post #21683811]
Do I need galvanic isolation for measurement and switching?
Yes. Isolate the measurement path with a small transformer that also steps voltage down. Isolate control paths with electromechanical relays or appropriately rated drivers for breaker coils. Even if a breaker’s input is isolated, you may still need a driver stage to meet coil current or voltage. [Elektroda, Anonymous, post #21683818]
Can small domestic loads really change grid frequency?
On a large interconnected grid, single‑home load changes cause only slight, momentary frequency shifts. In a small, controlled lab system, deliberate load steps are visible and useful for experiments. “Any load change … will cause a frequency change,” but magnitude depends on the system’s size and inertia. [Elektroda, Anonymous, post #21683813]
Is Arduino enough, or should I use a faster board?
Arduino can work, but higher‑clock MCUs or SBCs improve timing resolution and processing. Teensy, Raspberry Pi, or Beaglebone provide more headroom; Linux SBCs also simplify raw data capture for later analysis. If you’re constrained to Arduino, optimize timers and interrupts carefully. [Elektroda, Anonymous, post #21683816]
How should I model this in MATLAB/Simulink before building?
Create blocks for a voltage source, frequency measurement, controllable three‑phase loads, and breaker logic. Define frequency thresholds to trigger shedding or restoration. Validate timing and control logic in simulation, then port thresholds and logic to your Arduino for hardware testing. [Elektroda, Anonymous, post #21683817]
What is a comparator and why use it here?
A comparator outputs a digital high or low depending on the input’s instantaneous voltage. With an AC sample, it turns a noisy sine into a clean square wave with sharp edges. That clean edge makes timer‑based period or edge‑count measurement stable and repeatable. [Elektroda, Anonymous, post #21683809]
How do I switch three‑phase loads safely from a microcontroller?
Keep the MCU at low voltage. Use isolated relay interfaces or properly rated drivers to actuate contactors or breakers. Verify the breakers’ control inputs; some are isolated low‑voltage coils, others need specific drive currents and protection. Maintain isolation barriers between mains and logic. [Elektroda, Anonymous, post #21683818]
Quick how‑to: measuring frequency on Arduino Uno (3 steps)
- Square the conditioned AC sample with a comparator and feed a digital pin.
- Use an external interrupt to capture edges and read a hardware timer.
- Compute frequency from period or count edges within a fixed gate time.
[Elektroda, Anonymous, post #21683809]
How do I choose thresholds to shed or restore loads?
Define upper and lower frequency limits around nominal. When frequency drops below the lower limit, shed selected loads; when it rises above the upper limit, restore them. Your prototype can emulate grid logic by reacting “when the system frequency rises or falls past the given tolerances.” [Elektroda, Anonymous, post #21683814]
What’s an effective control loop for demand‑side response on a bench setup?
Measure frequency continuously, apply hysteresis on thresholds to avoid chatter, and switch loads in priority order. Log frequency and switching events to tune thresholds. Start with coarse steps, then refine timing and load sizes for stability and minimal overshoot. [Elektroda, Anonymous, post #21683810]
How can I log data for my dissertation?
Use a faster MCU or a Linux SBC to timestamp frequency, voltage, and switch states. Store raw data to files for replay and analysis. This makes it easier to validate controller behavior and produce publication‑quality plots. [Elektroda, Anonymous, post #21683816]
What is the Arduino Uno in this context?
It’s a 16 MHz microcontroller board suitable for timing edges and controlling relays. Its limited clock speed and non‑disciplined oscillator affect frequency resolution and absolute accuracy, so consider calibration or a higher‑quality clock if needed. [Elektroda, Anonymous, post #21683811]
What edge cases or failures should I plan for?
Interrupt storms or long ISRs can delay edge capture and distort period measurements. Oscillator drift skews absolute frequency. Mitigate by minimizing ISR work and calibrating timebase. Document these sources of error and their impact in your report. [Elektroda, Anonymous, post #21683811]
