The interesting block shown in Figure 1 can be used in several projects involving mechatronics and robotics.
Figure 1 – The circuit
If S1, S2, and 83 (sensors) are closed momentarily, relay K1 reverses the direction of the motor. But if the activated sensor is S1, the relay K2 is also activated, and the motor reverses direction and reduces its speed.
The reduction factor is given by the number of diodes used from D4 to D7. In this case, four diodes cause a voltage drop of about 2.8 V in the voltage applied to the motor.
The circuit is based on articles MEC053E and MEC055E. The circuit can adapt other blocks for the same application.
