This actuator type is driven by a direct current voltage (VDC) input signal. The shape of this input signal will determine what the resulting haptic effects feels like. A variety of input signal shapes can be used to create a variety of differentiated haptic effects. The range of these signals can be anything from a simple square wave input which will create a simple bump effect to a more complex time line of pulses and triangular shaped signals that can be combined to achieve a ramped effect that is actively damped to end it.
Driving the Johnson Electric haptic actuators is commonly done utilizing one of the following ways:
Straight Square Wave: This method is utilized in a lab environment with a signal generator and solid state switching mechanism to drive power to the coil.
Digital PWM: This method uses a trigger from a touch surface to activate a micro processor which will control the shape of the input signal pulse based on a predefined effect linked to the touch event. The microprocessor will also drive the solid state switching device (FET) which serves as the mechanism to transfer power to the actuator coil.
Varying the shape of the input signal will have an impact on the haptic effect that the end user feels. Examples of Width, Amplitude and Edge Variations are shown. Varying the width of an input signal will vary how long the pole pieces are attracted together. Changing the amplitude of the input signal will increase or decrease the intensity of the haptic effect. Finally, altering the leading or trailing edge of the input signal will impact the harshness of the haptic effect. The input signal can be a single input pulse or multiple pulses as shown here.