How to manage cell phone load

One of my friends turned to me with this request: they say, I want the fireplace to turn on in the garage on a call from a cell phone. He has a workshop there, and it’s cold in the mornings, so he wants to turn on the fireplace two or three hours before arrival. Everything is very simple: he turns on the fireplace by phone, and two hours later, if he does not come, the fireplace will simply turn itself off.

Talk that this is easier to do if you buy a programmable relay did not convince him. Apparently, he might not have appeared there on some days, but this was not amenable to any accounting when programming the relay. And he would spin the counter there while the fireplace was warming an empty room.

Nowadays, there are already many industrial devices that are controlled by the GSM (Global System for Mobile Communication) standard — a digital standard for mobile communications or a now familiar mobile phone. it security alarm, various control cabinets for industrial equipment, or even just separate sockets.

Naturally, my friend simply did not find such money, and the phone was already lying around idle. Yes, apparently, he’s not the only one if a sufficient number of circuits are posted on the Internet, from the simplest single-channel to the most complex and serious ones that control several channels.

So I was asked to do device for turning on the fireplace in the garage using a cell phone. To familiarize themselves with the question, a number of such schemes were viewed (and suddenly something will be possible to simply repeat someone else's, already ready).

Some schemes had redundant capabilities, because it was about managing only one load, and not eight or at least four. Schemes containing a large number of parts were also scared away. Others required a phone with auto-pick up handset when connected to the headset jack.

One circuit, contained only one transistor with a sensor in the form of an inductor and a microcontroller. The microcontroller in that circuit seemed to act only as a digital filter, protecting against false alarms from interference.

The purpose of the scheme was simply to reboot the remote computer server. When freezing, they simply pressed a button on the phone, the computer rebooted and continued to work. It was decided to go along such a path, namely, to receive a signal from the phone in a similar way, without getting confused in the wires, without connecting to the phone.

Actually, any scheme has its own advantages and disadvantages, so you should not think that developing your own scheme was the result of thoughts quite seditious: “They say they didn’t understand what, but everything turns out to be so simple and my circuit will be better than everyone else.” Not at all, there were no such thoughts, it was just decided to make the device out of what was already available.

After several experiments with an inductive sensor (until the phone rings, the phone emits pulses that immediately turn on the device), it was decided to use just a microphone from the telephone, because the faulty device was at hand.

The control algorithm is the simplest: having received a call on a cell phone, the device simply turns on the fireplace, and after two or three hours just turns it off. In this case, it is possible to re-enable the call from the phone when everything is already off. A condenser microphone was used as a call sensor.

The article in which I describe in detail the composition of the device and the operation of the fireplace control circuit by telephone turned out to be large, but interesting. In this regard, I decided to issue it in the form of a small practical guide (step-by-step instructions) in the format of an e-book.

You can download a step-by-step instruction on how to independently assemble and configure a load control device via a cell phone at this link:

http: //e.imadeself.com/Electrik_da.zip

I will be glad if this e-book is useful to you!

Boris Aladyshkin