Design of an Embedded System for Real-Time Temperature and Humidity Monitoring of Pharmaceutical Cold Chain in Katsina State

Cold chain integrity for vaccines and temperature-sensitive pharmaceuticals in Katsina State is compromised by the absence of continuous automated temperature monitoring in many storage and transport links, resulting in undetected temperature excursions that degrade product efficacy. This study designs an embedded system for real-time temperature and humidity monitoring of the pharmaceutical cold chain in Katsina State, targeting health facility vaccine refrigerators and pharmaceutical cold stores. The monitoring unit employs a DHT22 temperature and humidity sensor, an ESP8266 Wi-Fi microcontroller module, a micro-SD card for local data logging, and a GSM SIM800L module as a backup communication channel. Temperature and humidity readings are recorded at five-minute intervals and transmitted to a cloud-based MQTT broker accessible via a web dashboard displaying real-time readings, historical trends, and excursion alerts. When temperature exceeds the 2 to 8 degrees Celsius vaccine storage range, an SMS alert is immediately sent to the facility officer and district health officer. Battery backup sustains monitoring for twelve hours in the event of mains power failure. A prototype unit was deployed at a health facility vaccine store in Dutsin-Ma LGA, Katsina State, for a six-week monitoring period. During the monitoring period, three temperature excursion events were detected, two associated with refrigerator door ajar incidents and one with power failure, none of which had been identified under the previous manual monitoring system. Total component cost per monitoring unit was below twelve thousand naira. Keywords: cold chain monitoring, temperature sensor, IoT, vaccine storage, Katsina State.