Measure rotational period, frequency, and angular speed using either Gate A or Gate B.
Period T = N Δt (N: Number of Slits)Frequency f = 1/TAngular Speed ω = 2πf
Δt is calculated from consecutive midpoint timestamps from the same gate: Δt = t₂ − t₁. The displayed time is (t₁ + t₂)/2. Arduino blocking durations are ignored. The first reading from each gate initializes the timestamp and does not create a measurement.
Status: Arduino not connected
Raw Serial Data
Latest Measurement
Measurement
Value
Gate
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Time t (s)
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Time Interval Δt (s)
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Period T (s)
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Frequency f (Hz)
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Angular Speed ω (rad/s)
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Angular Speed vs. Time
Measurement Data
No.
Gate
Time t (s)
Δt (s)
Period T (s)
f (Hz)
ω (rad/s)
Copy Data places tab-separated values on the clipboard so they can be pasted directly into Excel. The table displays the latest 300 measurements; Copy Data includes all retained measurements (up to 100,000).
按下 Copy Data 可將以定位字元分隔的數據複製到剪貼簿，直接貼入 Excel。表格顯示最新的 300 筆量測資料；Copy Data 則會包含所有保留的量測資料（最多 100,000 筆）。
This web application was developed with AI assistance for NTHU General Physics Laboratory. Program development: Lab Maker Project.
Arduino Example Program
/*
Photogate Timer for NTHU General Physics Laboratory.
This program uses two photogates (Gate A and Gate B) to measure the motion of an object.
For each photogate, the program records:
1. Time: the midpoint time of the blocking interval (s)
2. Δt: the duration that the photogate is blocked (s)
Output example:
Gate A: 1.253426, 0.018532
Gate B: 1.684720, 0.017916
For rotational motion, the web page uses consecutive midpoint times from the same gate.
The interval is Δt = t2 - t1 and its time is (t1 + t2)/2.
The Arduino blocking duration is ignored.
Then T = N * Δt, f = 1/T, and angular speed = 2*pi*f.
*/
int gatePinA = 2; // Photogate A: digital pin 2
int gatePinB = 3; // Photogate B: digital pin 3
int ledPin = 13; // Built-in LED
int gatemode = LOW; // LOW when the photogate is blocked. Change to HIGH if needed.
unsigned long t0; // Starting time
unsigned long tNew, tLast; // Entering and leaving times
float time, deltat; // Midpoint time and blocking duration (s)
void setup() {
Serial.begin(115200); // Start serial communication
pinMode(gatePinA, INPUT_PULLUP); // Gate A input (keep HIGH when disconnected)
pinMode(gatePinB, INPUT_PULLUP); // Gate B input (keep HIGH when disconnected)
pinMode(ledPin, OUTPUT); // LED as output
t0 = micros(); // Set the starting time
}
void loop() {
// Gate A
if (digitalRead(gatePinA) == gatemode) { // Gate A is blocked
tNew = micros(); // Object enters Gate A
digitalWrite(ledPin, HIGH); // LED on
while (digitalRead(gatePinA) == gatemode) { ; } // Wait until object leaves
tLast = micros(); // Object leaves Gate A
deltat = (tLast - tNew) / 1000000.0; // Blocking duration (s)
time = (tNew - t0) / 1000000.0 + deltat / 2.0; // Midpoint time (s)
digitalWrite(ledPin, LOW); // LED off
Serial.print("Gate A: ");
Serial.print(time, 6); // Midpoint time (s)
Serial.print(", ");
Serial.println(deltat, 6); // Blocking duration (s)
}
// Gate B
if (digitalRead(gatePinB) == gatemode) { // Gate B is blocked
tNew = micros(); // Object enters Gate B
digitalWrite(ledPin, HIGH); // LED on
while (digitalRead(gatePinB) == gatemode) { ; } // Wait until object leaves
tLast = micros(); // Object leaves Gate B
deltat = (tLast - tNew) / 1000000.0; // Blocking duration (s)
time = (tNew - t0) / 1000000.0 + deltat / 2.0; // Midpoint time (s)
digitalWrite(ledPin, LOW); // LED off
Serial.print("Gate B: ");
Serial.print(time, 6); // Midpoint time (s)
Serial.print(", ");
Serial.println(deltat, 6); // Blocking duration (s)
}
}
