<![CDATA[ABSTRACTThe objective of this research was to produce prototype of an early warning system basedon SMS for detection the rising level of ammonia gas in wastewater treatment of leather tanningindustry. The systems consist of three parts, those were data input, data processing, and output.Ammonia gas sensor as a detector that produces an analog Direct Current (DC) voltage. Analogto Digital Converter (ADC) pin on the microcontroller received an analog DC voltage to beprocessed. ADC readings done through the Liquid Crystal Display (LCD) while the GlobalSystem for Mobile Communications (GSM) modem was used to send Short Massage Service(SMS). This early warning system worked by determining a threshold value. SMS would be sent tohand phone number of job holder, if the ADC value exceeded the specified threshold value. Resultobtained was the ammonia gas sensor model are MQ137 based on SnO , Arduino Uno as 2microcontroller module based on Atmega 328P microcontroller, and General Packet RadioService (GPRS) Shield as GSM modem that compatible with the Arduino Uno R3 pin.Keywords: wastewater treatment, tanning industry, amonia gas, SMS, MQ 137ABSTRAKTujuan penelitian ini adalah untuk mendapatkan sebuah rancang bangun (prototipe) sistemperingatan dini melalui SMS atas kenaikan aras gas amoniak di pengolahan air limbah industripenyamakan kulit. Sistem ini terdiri dari data masukan, pengolah data, dan keluaran. Sensor gasamoniak sebagai detektor menghasilkan tegangan listrik arus searah (DC) analog. Pin converterdigital ke analog (ADC) pada mikrokontroler menerima tegangan listrik DC analog untukselanjutnya diolah. Pembacaan ADC dilakukan melalui Liquid Crystal Display (LCD)sedangkan modem Global System for Mobile Communications (GSM) berfungsi untukmengirimkan SMS. Sistem peringatan dini bekerja berdasarkan penentuan nilai ambang batasaras gas amoniak. Apabila pembacaan detektor melebihi nilai ambang batas aras gas amoniakyang ditentukan, maka peringatan dini akan dikirimkan lewat SMS kepada nomor petugas. Hasilyang diperoleh adalah sensor gas amoniak model MQ137 dengan bahan dasar SnO , modul 2mikrokontroler berupa Arduino Uno versi R3 berbasis mikrokontroler Atmega 328P, modemGSM model General Packet Radio Service (GPRS) Shield yang sesuai dengan pin Arduino Unoversi R3.Kata kunci: pengolahan air limbah, industri penyamakan, gas amoniak, SMS, MQ137]]>
