Power Outage Monitor

Background

I like using real-life problems for projects otherwise its just an experiment with no real application. I live in South Africa where regular power outages occur often in some areas. This causes issues when one is on holiday away from home without the ability to know what's going on there. Specifically ensuring that the power comes back on after a power interruption and that critical appliances like fridges and freezers are not off for too long is essential.

Idea

I wanted to create a tool that is small, cheap and easy to use for the normal Joe Soap. The aim is to house the project inside a small enclosure that is attached to a wall plug - the idea being to make it almost as small as a normal phone charger.

Hardware Design

The design is centered around the ESP8266 chip connected to the GSM GPRS A6 module with a few circuits to perform various tasks like

• Mains power detection circuit (simple bridge rectifier with a few resistors to get the levels right).

• Battery management and switch-over circuit to ensure continuous power once the mains power is gone. A Lithium Polymer (LiPo) battery is used for this. I am using a TP4056 chip for this together with protection circuits for the battery.

• Temperature sensing circuit. I am looking at using a simple DHT11 (or DHT22) for temperature and humidity sensing.

• Appliance control circuit allowing up to 2 appliances to be powered. This would be a basic relay that should handle the current required for the appliances.

Design Principle

The main principle is for the user to plug a SIM card into the A6 module and plug the unit into a powered wall socket. Then the user sends an SMS to the device that will register the user's phone with the device. Thereafter the user will receive SMS notifications once power goes down comes back on, if temperature rises above a preset level, etc.

The user will have the ability to configure the device's setpoints, levels, request the log of etc. through SMS.

In addition to the SMS, Cayenne will be used to control the view and edit set-points, see the current status of appliances, view temperatures, see the status of the battery, etc. Cayenne can unfortunately only be used when mains power is present since the WiFi of the 8266 will only work via a router (unless of course I can manage to set up and internet connection via the A6 module).

For the appliances to be controlled, they need to be physically connected to the device. This topic will be covered in the Prototyping stage.

Costing

I bought my stock from www.aliexpress.com. The A6 module is less than $4 when bought in single units and is the most expensive item yet. My aim is for the project to cost less than $30 with some versions of the product costing less - obviously then with less functionality.

Prototyping

Still to come...

Detailed Design

Still to come...