![]() ![]() We can replace a set of manual switches of electromechanical relays, and have a forward and reverse button or switch, and even use solid-state CMOS 4066B quadrilateral two-way switches.īut another very good way to achieve two-way motor control (and speed) is to connect the motor to a transistor H-bridge circuit device, as shown below. However, using the switch in this way is dangerous because operating switches A + C or B + D together can short-circuit the power supply.Īlthough the above two circuits work well for most small DC motor applications, do we really want to operate different combinations of mechanical switches to reverse the direction of the motor, NO!. The switch combination A + B or C + D short-circuits the motor terminals, causing it to brake quickly. For example, the switch combination A + D controls the forward rotation, while the switch B + C controls the reverse rotation, as shown in the figure. Mechanical switches are arranged in switch pairs and must be operated in a specific combination to operate or stop the DC motor. The second circuit is slightly more complicated and uses four single pole single throw (SPST) switches arranged in an “H” configuration. By switching the contacts, the power of the motor terminals is reversed, and the motor reverses its direction. The first circuit uses a single double pole double throw (DPDT) switch to control the polarity of the motor connection.
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