Clap-Operated Remote Control for Fans

You should find this clap-operated remote control system quite useful in summers as it would enable you to control the speed of your fan or cooler, besides switching it on or off. Normally, a fan has three to five speeds but this remote control can control up to ten-step speed control fan. Besides, it provides visual indication of the speed of the fan.

This circuit may be considered in four parts: sound-operated trigger pulse generator, clock pulse generator, clock pulse counter and load operator, as shown in the block diagram (Fig. 1).

The trigger pulse generator is built around transistor BC148 which amplifies the audio signals in class-C mode. The clock pulse generator stage is based on NES55 IC while the clock pulse counter is based on the popular decade counter IC CD4017BE. The load operator stage is constructed in two ways. One method mentiond here is to use three BEL187 (or AC187) transistors, so that they could operate three separate relays. The other method, which excludes the relays and transistors, uses three triacs which have long life but include greater danger of electric shock.

The condenser microphone converts the sound of a clap into an electric signal and supplies it to the base of transistor BC148. The transistor provides a trigger pulse to pin 2 of monostable multivibrator IC NE555 timer. The duration for which the output of monostable multivibrator remains high is given by the relationship

T = 1.1R*C*.

In this circuit, the values of R* and C* are so chosen that the clock pulse duration is approximately one second, so that no more than one clap within one second can change the gear (and thus speed) of the fan.

The clock pulse is then applied to pin 14 of decade counter IC CD4017 which counts the clock pulses. This IC has ten outputs, viz, 0. 1, 2….9. The output number 0 (at pin 3) is high without any clock pulse applied to the IC. So we have used only output 1 at pin 2, output 2 at pin 4 and output 3 at pin 7. while output 4 at pin 10 is connected to reset pin 15.

Though all the ten outputs can be used to control ten separate relays or triacs, normally only three relays or triacs arc sufficient for this job. The first relay or the first triac is to control the first gear while the second relay or the second triac is used to control the second gear, and the last relay or triac is used to control the third gear.

A 100-ohm resistance is used in series with each LED. Green LED indicates the first gear, while the yellow indicates second, and the red LED indicates the third gear. The fan is switched off on the fourth clap.

The circuit can be assembled on a general-purpose circuit board. IC sockets should be used to protect the ICs from the soldering iron’s heat. Besides, the ICs can be replaced very easily if these are mounted on their IC sockets.

There is only one jumper used in the PCB of this circuit, which is from the collector of transistor BC148 via a 0.1 jd7 capacitor to pin 2 of IC 555.

Readers’ Comments:

The Clap Operated Remote Control for Fans in EFY May’92 issue is no doubt an excellent article, but it has not been fully explained. Forinstance, there are two jumpers (J1 and J2) in the circuit whereas in the last paragraph of the article only one is mentioned.

Besides, the article does not indicate how the input of fan is to be connected.



I have a few queries:

1. For assembly with triacs, how should the power be given to the circuit when it is transformerless?

2. Aren’t current coils required in series with the triacs?

3. Is it advisable to use IC 4022 instead of 4017?

4. Is it possible to use an infra-red transmitter and a receiver instead of condenser microphone?


As I wish to operate a relay by illuminating a torch using two cells, I have selected the second portion of the circuit (IC2 onward) and used an IC 555 circuit for triggering. But the operating range obtained is too low, which I wish to increase to about 10 metres.

SANTANU SA MANTA Bankura (W.B.) The author, Mr Narpat Singh Rana, replies:

Some confusion appears to have been created by excessive editing of my article. I’m therefore giving below the missing information.

The circuit may be powered after carefully assembling it. Green LED should glow on clapping once near the condenser microphone. On clapping again, yellow LED should glow and the second relay energise. On third clap, red LED should glow and the third relay energise. On fourth clap, the controlling circuit is reset,

The whole prototype, along with the relays, should be assembled in a transparent case so that the indicating LEDs are visible. The assembly should be fitted near the fan’s switchboard.

The diagram given above shows how to connect the assembly to the ceiling fan.

In triac assembly, power to the transformerless circuit should be given using a circuit such as the one shown below.

It should be kept in mind that the lower terminal of the power supply is common, and so the circuit should not be touched when working, from the safety point of view.

There is no need of using current coils in series with triacs. But all the triacs should be mounted with proper heatsinks, if necessary.

It is not advisable to use CD4022 instead of CD 4017 because much more gear system could be used with CD4017, if necessary.

It is possible to use infra-red transmitter and receiver, but it is beyond the scope of this article.

To control just one relay with torchlight, only pins 15 and 4 ofIC CD4017 should be used. To increase the range, 100k preset should be removed.

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