GSM Remote Control – 2 IN and 2 OUT
Part 1 – Introduction

By on January 8, 2011

It allows you to remotely control up to two different electrically controlled units and to remotely read the condition of as many devices or the presence of tension on power lines.

We describe the simple remote control, obtained by adding to the regular circuit, two optocouplers and both relays, together with the basic components. The circuit we propose has two main functions:  the first one is to remotely control electric, electronic, or electrically managed units; the second one is to remotely acquire electrical conditions, i.e. the status of sensors and any kind of device whose situation can be expressed through a logical level or a voltage value.

TDG133 Connection

2 IN and 2 OUT Connection

To do so, there is an important set of commands to be sent via SMS. In particular, the instructions allow the user to: enable or disable each of the present outputs, by impulses (defining the activation time) and in bistable mode; interrogate the unit to obtain the status of one of these outputs. The latter is essential when you have forgotten the last command sent, or to ensure a command SMS has performed the desired order. Through an appropriate message, the remote allows you to establish whether, in case of black-out, it has to keep in memory the pre black-out condition and reestablish it when power is restored; useful to avoid that, in case of accidental switching, when the unit is started, the relays lose the settings given by the user via remote commands sent via SMS with a mobile.  Regarding the functions of the inputs, we have set commands used to know, any time, the condition of one of both inputs; there is also a remote alarm, which is the generation of SMS and calls to the numbers in a list made of 8 people (the same users allowed to remotely set and manage the device) upon the presence of a given condition, this is also to be set via SMS commands. The inputs sense the presence/absence of voltage. We can tell the remote to consider this presentence or absence, as well as a change of status as an alarm. Please note it is not necessary to answer the call, it is just a couple of ring tones sent to the called mobile; when hearing the ring the user knows he has to query the remote to find out the reason of the call. Combining a call with a SMS can be useful for absent-minded people or for those who keep the phone out of reach, in order to be alerted about the arrival of a message that was probably unnoticed. All query commands (intended for outputs or inputs) determine that the system sends a SMS, with the requested data, to the phone number (if it can be identified) that sent the commands. For every condition that provides for the transmission of unsolicited messages manually, i.e. those regarding the remote alarm functioning (change in input status, interruption and reestablishing of power, circuit start-up), the remote allows you to define the text sent to the eight numbers in the list of the people to be warned.

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