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162 Build Your Own Electric Vehiclereleasing the pedal means the motor is off (no creep). Pressing the pedal to a certainpoint sets a certain motor voltage, which means a certain speed. Pressing hard givesyou a constant rate of acceleration (because the controller is in current limit; constantcurrent 5 constant torque). Release the pedal, and it simply coasts (unless you haveregenerative braking, in which case you can configure what it does).DC Motor Controller—The Lesson of the Jones SwitchThe easiest way to vary the DC voltage delivered to a DC motor is to divide its steady,nonvarying DC component into smaller pieces (see Figure 7-1). The average of thenumber or size of these pieces will be a resultant DC voltage that the motor “thinks” it isreceiving. At the top left of Figure 7-1, the value of the voltage delivered to the motor isV motor5 ((t on)/(t on1 t off)) 3 V battery5 (t on/T) 3 V battery5 K dcV b(1)This equation shows that the voltage delivered to the motor is proportional to theamount of time the pulse is on versus the total length of the period. As t off>> t onin theleft-hand graph, the average voltage (V) the motor receives is only equal to a smallFi g u r e 7-1 Summary of Jones switch PWM chopper controller characteristics.