The sprayer has widely been applied in the agricultural and
the gardening industry. Especially, it is often used civil
application such as the sanitation of larger stock cultivation,
public place, and school. The output liquid pressure of the
employed electric sprayer, which is supplied an independent
rechargeable battery, is generally controlled by a step-down
buck converter. In experiments, the pump of electric sprayer is
driven by a DC (brushed) motor. The supplied voltage of DC
motor is regulated by the buck converter via a PWM
technology. Some protection circuits such as over-current,
over-temperature, and short circuit etc and friendly operating
interface are included in the system controller of electric
sprayer. Taken the working performance, manufacturing cost,
using safety, and operating reliability into consideration, an
electric sprayer with pressure- programmable capacity is then
successfully designed. The system controller design of DCmotor
is a close-loop control structure [6,7]. In addition, the
requirements of circuit protection or equipment, the current
value of DC motor will be necessary to be often dynamically
measured by a suitable current censor. We are hope to
furthermore improve the performance of electric sprayer and
free to increase the manufacturing cost. One new sensorless
speed measurement method based on the motor current will be
presented here. This method is mainly implemented by using
few of hardware devices.