It had been a long time since I wanted to make a building automation system. In fact it was the first product I ever dream’t of making. Time passed and I didn’t quite find the time and interest to venture into it as I felt that building automation is an old concept and there are too many players doing the same stuff.

So, I designed this board, which can control the relays on board, based on the inputs provided either from the cloud or from a call using DTMF.

Features : For the first iteration we designed it to have the following features,

• 4 cube Relays driven by MOSFET’s to control 110V to 230V AC appliances
• SIM800C 2G Quadband GSM module for cloud/call connectivity with micro SIM card connector
• External Whip Antenna with right angle SMA connector
• MP3 player with micro SD card
• STM32 Cortex M0 Low power MCU with RTC
• Switching power supply to take inputs from 5V to 24V DC
• DC power jack for power input
• SWD connector for programming and debugging

How the DTMF version works :

• Insert the SIM card and SD card containing MP3 files into the device.
• Power on the device using a DC adapter
• Network LED blinking every 3 seconds will indicate that the device has connected to the network.
• Wait for 30 seconds for initialization and ring the SIM card number.
• Your call will be auto answered after 2 rings (Security can be added to answer only specific numbers)
• An audio will be played on the call and you should hear, "Welcome to Valetron Systems, Press 1 to control Device number 1, Press 2 to control Device number 2, Press 3 to control Device number 3, Press 4 to control Device number 4"
• You press 1 on the dial pad of your phone and you should hear, "You have selected Device number 1, Press 1 to turn ON device number 1, Press 2 to turn OFF device number 1"
• You press 1 on the dial pad of your phone and you should hear, "Device number 1 turned ON, Press 2 to turn off device number 1, Press # to return to main menu". At the same time, Relay 1 will be turned on and LED 1 will be turned on indicating that Relay 1 is in ON state now.
• You press # and you will go back to hearing the Welcome message.

This is how the DTMF control of the device works.

State machine based code:

The code is written as a state machine and each state can be changed to perform a different action easily. If the user knows the flow, when he calls, he can quickly enter the inputs so that he doesn't waste time waiting to hear the audio instructions.

Multiple language support :

We can also add different language support and ask for selection of language in the welcome message and switch to playing only that language audio for that specific user.

Applications :

This board can be used as a,

• DTMF controlled home automation device.
• Cloud/GPRS/IOT based home automation device.
• SMS based building/home automation device.
• Voting system where people can call and leave their feedback for small businesses who cannot afford a expensive IVRS system.
• IVRS booking system where people call and enter inputs to book a service like entering a gas booking number for ordering a cylinder refill.

The first iteration of the board was successful and its available for purchase for trying it.

Whats in the package when you buy it :
1 Nos VALTALK-V1 board with Whip antenna and 4 nos 12V relays assembled. The demo firmare is loaded on the board and you can get started controlling any AC/DC appliances by calling the SIM card number using DTMF.

Note : microSD card is not present in package. Audio files used in demo are zipped and sent to you. Just copy them in your microSD card in MUSIC folder and you should be good to go.

You will need, 1 - 9V/12V DC power adapter to power the board 2 - 2G MICRO SIM card for network connectivity. 3 - MICRO SD card for copying Audio files.