I’m using the Pololu 150:1 Metal Gearmotor 37Dx73L mm 24V with 64 CPR Encoder (Helical Pinion) along with the Motoron M2S18v18 Dual High-Power Motor Controller Shield for Arduino (Connectors Soldered). To estimate the motor’s RPM, I wrote some Arduino code based on encoder readings. However, the RPM calculated by the code seems significantly off compared to my manual count. For example, when I set the motor speed to 800, my own count gives me approximately 72 RPM, but the Arduino without Labview reports around 18 RPM. If I use Labview and Visa series communication, the computed RMP from Arduino becomes 168 RPM. According to the website, the no-load RPM is 68. Could anyone help me identify if there’s an issue with the way I’m calculating RPM? I’d appreciate any suggestions or corrections. Here’s the code I’m using for RPM calculation
#include <Wire.h>
#include <Motoron.h>
#include <Encoder.h>
MotoronI2C mc;
Encoder myEnc(2, 3); // yellow = 2, white = 3
const long counts_per_rev = 38400;//64*4*150
long lastCount = 0;
unsigned long lastTime = 0;
void setup() {
Wire.begin();
mc.reinitialize();
mc.clearResetFlag();
Serial.begin(9600);
}
void loop() {
// Read speed from LabVIEW
if (Serial.available()) {
int speed = Serial.parseInt(); // Expect -800 to 800
mc.setSpeed(1, speed);
}
// Read encoder counts
long currentCount = myEnc.read();
float revolutions = (float)currentCount / counts_per_rev;
// Calculate RPM every 100ms for smoother plot
if (millis() - lastTime >= 100) {
long diff = currentCount - lastCount;
float revs = (float)diff / counts_per_rev; // revs in 0.1s
float rpm = revs * 60.0 * 10; // convert to RPM (10 times because 0.1s interval)
// Print for Serial Plotter (comma separated)
Serial.print(revs);
Serial.print(",");
Serial.println(rpm);
lastCount = currentCount;
lastTime = millis();
}
//delay(20);
}