CoilPad - Creating a Micro-Heater

CoilPad is a flexible, ultra-thin sticker coil intended to be used as a magnetic actuator. However it can also be hacked into a micro-heater for some specialized applications.  actuator that can also function as a micro-heater. 

By adjusting the PWM waveform, you can vary the heat generated.

Safety Considerations

• Always handle CoilPad with care, as it can become hot.
• Ensure that the surface it is attached to can withstand high temperatures.
• Avoid direct skin contact when powered.
• Use proper insulation if needed.

How It Works

When powered at a constant 5V, CoilPad can reach up to 100°C. This makes it suitable for applications requiring a compact and seamless heating element. Varying the input voltage, directly controls the output heat - so by powering the CoilPad with a Pulse width modulation (PWM) signal instead of constant power, we can also vary the heat. A higher duty cycle results in increased heat output, while a lower duty cycle maintains a lower temperature.

Heat Control

Several factors affect the heating performance of CoilPad:

• Voltage Level – The maximum operating voltage is 5V. Higher voltages are not recommended as they may cause overheating or damage.
• Duty Cycle – Adjusting the duty cycle of the PWM signal controls the heat output, allowing precise temperature regulation.
• Thermal Dissipation – The surface to which CoilPad is attached will affect how heat is distributed and retained.

Using DriveCell to Control Heat Output

If you are using the DriveCell library, you can easily control the CoilPad as a micro-heater with the following example:

#include <drivecell.h>

#define HEATER_PIN1 2
#define HEATER_PIN2 3
DriveCell Heater(HEATER_PIN1, HEATER_PIN2);

void setup() {
  Heater.Init();
}

void loop() {
  Heater.Drive(true, 100); // Maximum heat output
  delay(5000);
  
  Heater.Drive(true, 75); // Reduce heat to 75%
  delay(5000);
  
  Heater.Drive(true, 50); // Moderate heat at 50%
  delay(5000);
  
  Heater.Drive(true, 25); // Low heat at 25%
  delay(5000);
}

Understanding the Functions:

• Init() → Initializes DriveCell and sets up the input pins.
• Drive(bool direction, uint8_t power_percent)
  • direction: true (activates the heating element)
  • power_percent: Adjusts the heat output (0 to 100%)

⚠ Note: The Drive() function uses a high-speed PWM timer, making it compatible only with CodeCell and ESP32-based devices.

If you're using a standard Arduino, you can control the heat output using the following code. However, ensure that the waveform frequency is set correctly ideally ~20kHz

#define HEATER_PIN 2

void setup() {
  pinMode(HEATER_PIN, OUTPUT);
}

void loop() {
  analogWrite(HEATER_PIN, 255); // Maximum heat output
  delay(5000);
  
  analogWrite(HEATER_PIN, 191); // 75% Heat
  delay(5000);
  
  analogWrite(HEATER_PIN, 127); // 50% Heat
  delay(5000);
  
  analogWrite(HEATER_PIN, 63); // 25% Heat
  delay(5000);
}

Conclusion

As we've learned by utilizing PWM control, CoilPad can be hacked into a micro-heater! Check out the DriveCell GitHub Repository for more code examples and technical documentation!