Water is a very important element of human life because water can be used for various purposes, one of which is in the household sector. There are several processes in water treatment, one of which is the coagulation process which is where the addition of Aluminum Sulfate dosage is made, but at PDAM Karang Pilang this process is still carried out manually or the jar test method. Therefore, in this study, a prototype system for the Automation of Addition of Aluminum Sulfate Doses has been designed using the fuzzy logic controller method. The type of fuzzy method used is the Mamdani type. This prototype is equipped with 2 sensors, namely the E-201-C pH Sensor and the SEN0189 Turbidity Sensor. The actuator used is a 12-volt peristaltic dosing pump and the microcontroller used is Arduino Uno. From the results of the design of the static characteristics of the pH sensor E-201-C and Turbidity SEN-0189, it has the highest accuracy rates of 99.8% and 99.5% in pre-sedimentation water samples. In testing the dynamic response of pH and Turbidity, it was found that the rise time values were 15.32 seconds and 25.49 seconds, the max overshoot was 4.76 % and 9.88 %, Steady State Error was 0.36 and 0.51 and the Settling time was 54.15 seconds and 83.27 seconds.