In doing research in the laboratory, it is often to mix two or more chemicals. Mixing is done to produce two or more homogeneous samples. In this research, an automatic chemical mixer will be designed. In designing the mixer using a DC motor as a propulsion, Arduino works as a microcontroller of the speed regulator, timing speed regulator, and speed control sensor to get the motor rotation speed. Hence, the description of RPM and timer can be displayed. The test of the tool is done on two parts that is RPM and timer. The RPM test is performed by comparing the motor rotation speed value in the final task module with the speed displayed on the tachometer speed measuring device. The timer test is performed by comparing the length of rotation of the motor displayed on the final task module by stopwatch comparator. Based on the motor speed measurement, the average error at motor speed is low 1.4%, medium 2.5%, and high 2.54%. In addition, the average error of the timer is 1 minute 0.03%, 2 minutes 0.1%, 3 minutes 0.05%, 4 minutes 0.016%, and 5 minutes 0.03%. The result is still within the permissible tolerance of not exceeding 5%.