In few of my previous articles we discussed a handful of GSM remote control circuits using ordinary cell phones as the modem. All those designs incorporated the ringtone of the cell phone as the triggering signal. In this post we'll learn how the same could be achieved but by using the vibrator feature of the modem cell phone.

Using the Vibration Mode as Trigger


In our previous GSM remote control designs we used those cellphones as the modem which had the specific ringtone selection facility for a specific assigned number, here the modem will need to have a vibrating feature for the specific assigned number selected as the triggering number, this is important in order to achieve a fool proof operation of the system.

The idea is simple, it's to detect the vibration from the cell phone body, convert it into a toggling signal and control the desired load or gadget ON or OFF.

For detecting and using a vibration signal to trigger a relay, we'll need a vibration detector circuit as shown in the following diagram:

Circuit Diagram



Transistor Amplifier


The circuit is basically a transistorized high gain amplifier where a piezo is used as the vibration sensor.

The vibrations from the piezo generates a correspondingly oscillating voltage at the base of T1 which is appropriately amplified by all the following transistor stages consisting of T2, T3, T4, T5, T6 and the associated parts.

The amplified DC signal is finally applied across the connected relay which toggles in response to the detected vibrations over the piezo.

Since a cell phone vibration could have an inconsistent vibrating rate could result in a corresponding oscillatory response over the relay switching.

To avoid this a high value capacitor in the range of 500uF should be connected directly across the base and emitter of T6, this will ensure that T6 sustains its conduction even while the cell phone vibrations are intermittently absent.

The Flip Flop Circuit


In the above mode, the relay stays activated only for so long as the vibration signals are produced, in order to translate the reaction into a toggling effect a flip flop circuit becomes imperative. The following simple 4093 IC based design becomes perfectly compatible for the required conversions.





The input trigger may be connected to the pole of the relay, while the N/O of the relay will need to be connected with the positive of the supply.

Alternatively, the relay could be entirely eliminated, and the "input trigger" of the above flip flop circuit directly connected with the collector of T6.

Once this is done the relay would respond with alternate ON/OFF toggling motion each time the modem cellphone is called by the owner or the user.

The relay of the flip flop could be used for switching any desired appliance or in case it's deployed inside a vehicle could be implemented to operate the central locks and the ignition system for achieving a complete cell phone operated security feature.

Using Piezo as the Sensor


C1 in the first vibration detector circuit could be a 0.22uF capacitor and must be employed only if the piezo is terminated over a longer distance from the circuit, otherwise C1 could be ignored.

Preferably the piezo must be situated close with the circuit board.

The piezo transducer is a 27mm ordinary device which are normally using in piezo buzzer circuits.

It must be appropriately housed inside a plastic enclosure for ensuring an optimal response from it.

The entire unit may be further enclosed inside a plastic box with the piezo assembly stuck on inner top surface of the box.

The modem cellphone must be directly placed over the above enclosure right on the outer opposite surface of the piezo assembly (see figure below)





The modem must be appropriately secured over this position so that the unit does not tumble away from the box while vibrating.

Now your cellphone vibrator based remote control circuit is ready and may be used for any desired GSM based remote control application and may be switched from any part of the world, just with a flick of a button.

Make sure that the vibrator is assigned to turn ON only for the specific numbers and not for the default numbers to ensure a foolproof operation of the unit.

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