Excellent to remotely control via GSM the activation of engines, lightening or watering systems and alarm systems. It sends commands through SMS as well as with DTMF dual tones and allows you to check if they were successful.
In this post we present the last application created from the development of the modular remote control we started describing in the issue …

Let’s now look into the schematic diagram; in it you can note the usual Microchip microcontroller governing the GSM/GPRS module activity, controlling the logical condition of the two opto-isolated inputs and managing the two relays. Moreover, the PIC interacts with the DTMF decoder in order to recognize the dual tones used for the phone selection in modern telecommunication systems; it …

On the construction perspective, the remote control does not present many difficulties, just the obvious ones that appear when working with circuits requiring superficial assembly components. As usual, there is a PCB with double plating where to mount all components.

The set of commands of this remote is divided into two categories: the SMS ones and the DTMF tones.
The former are simply summarized in the corresponding table, since they are the same as the ones described for remote 2 IN/2 OUT.
Here we will only describe in detail the DTMF commands, first stating that unlike those from SMS, that can be …