Understanding CoilCell Circuitry

CoilCell is a thin planar PCB coil built on a multi-layered PCB with an integrated driver that simplifies magnetic control. In this post, we’ll explore its circuitry and how it functions.

What is CoilCell?

CoilCell is a PCB-based planar coil that generate a magnetic field that can interact with magnets. It is available in two configurations:

• 1W CoilCell: Made from a 1.3mm thin, 4-layer PCB with a 70 turns spiral coil, with a peak magnetic field of 2.3 mT. 
• 2.5W CoilCell: Made from a 2.6mm thin, 14-layer PCB with a 200 turns spiral coil, with a peak magnetic field of 10 mT, which can be increased to 17 mT using an iron back-plate.

With its DRV8837 H-Bridge driver, CoilCell allows control of current flow, determining both magnetic polarity and strength via the 2 input signals.

The Heart of CoilCell: DRV8837 H-Bridge

Unlike the CoilPad (which requires an external driver) this CoilCell module has an integrated DRV8837 H-Bridge driver. It enables bidirectional current flow, allowing the coil to generate a north or south magnetic field:

• Magnetic North: IN1 = VCC/PWM, IN2 = GND
• Magnetic South: IN1 = GND, IN2 = VCC/PWM
• Off State: IN1 = GND, IN2 = GND

For added clarity, an onboard LED provides visual feedback, indicating the polarity of the output.

Key Features of the DRV8837:

• Overcurrent Protection
• Undervoltage Lockout
• Thermal Shutdown
• Supports up to 1.8A continuous current

These safety features help prevent damage from overheating or incorrect wiring, ensuring reliable operation.

Getting Started with CoilCell

To start using CoilCell, follow these steps:

1. Wiring CoilCell to Your Circuit

Solder the power and input pins to your microcontroller. 

• Setting IN1 high generates a north magnetic field
• Setting IN2 high generates a south magnetic field
• Setting both IN1 and IN2 to GND turns the coil off

The VCC must be connected to a maximum supply voltage of 5V.

If using multiple CoilCells, the side pads allow for easy daisy-chaining to share power and control signals across multiple units.

2. Coding with the CoilCell Library

To simplify programming we had a CoilCell library with easy to use functions.

Steps to Install the Library:

1. Open Arduino IDE
2. Go to Library Manager and search for “CoilCell”
3. Click Install
4. Load the example sketches to start experimenting!

3. Keeping things tiny

Use our CodeCell module which is designed to be pin-to-pin compatible with CoilCell. With CodeCell, you can add wireless control and interactive sensing, unlocking new possibilities for your projects.

Safety Tips & Heat Management

Heat Considerations

• The 2.5W 200-turn CoilCell can reach temperatures of up to 110°C - especially when combined with an iron back-plate.
• Ensure that 3D-printed parts or materials near the coil can withstand high temperatures.
• Reduce power output by adjusting the PWM duty cycle to manage heat generation.

General Safety

• Avoid direct contact with the coil when operating at high power.
• Use eye protection when working with small magnets that may be repelled at high speeds.
• Ensure any soldered wires or jumpers are non-magnetic to prevent unintended magnetic interference.

Conclusion

With the CoilCell module you have everything you need to start experimenting and build your own fun magnetic actuators! Check out the CoilCell Schematics here to explore its circuit design and start integrating it into your next project!