1 . Closed design , putter to the top will not out. 2 . Try to balance the top of the push rod , Can not withstand too much force. 3 . In order to prevent the motor from burning out when turing , external drive plate or motor current limit is recommended. Motor Driver Technical Datae Dual H-bridge motor driver , can drive two DC motors or a 4-wire two-phase stepper motore. The module supply voltage 2V-10V.Signal input voltage 1.8-7V. Single Operating urrent 1.5A current up to 2 5A , ow standby curent ( less than 0.1uA ) Built-in common conduction circuit, when the input pin is left floating,the motor does not malfunction Built-in thermal circuit with hysteresis effects (TSD ),without worring about motor stall Motor Driver: Power positive and negative reversed will certainly cause damage to the circuit . Output is shorted to ground or output short circuit , and the motor stall , the chip will heat protection , but in the nearor exceeding 10V voltage and current is 2.5A situation can also cause chip burned specification:12V colour:yellow Material:Metal + plastic size:11 x 2 x 2cm Package Contents: 1 * Model excavator arm 1 * Motor drive board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.