A "Clap On Clap Off" switch is an interesting concept that could be used in home automation. It works as a switch which makes devices On and Off by making a clap sound. Although its name is “Clap switch”, but it can be turned ON by any sound of about same pitch of Clap sound. The main component of the circuit is the Electric Condenser Mic, which has been used as a sound sensor. Condenser Mic basically converts sound energy into electrical energy, that in turns used to trigger 555 timer IC, through a Transistor. And triggering of 555 ic works as a Clock pulse for D-type flip-flop and would turn ON the LED, which will remain ON until the next clock pulse means until the next Clap/sound. So this is the Clap Switch which will turn ON with first Clap and turn OFF with the second Clap. If we remove the D-type Flip flop from the circuit, the LED will be turned OFF automatically after some time and this time will be 1.1xR1xC1 seconds, which I have explained in my previous circuit of clap switch. For better understanding, I recommend to study the previous circuit before study this one.

### Working Explanation

Here we are using Electric Condenser Mic for sensing the sound, transistor to trigger the 555 timer IC, 555 IC to SET & RESET the D-type flip flop and D-type flip flop to remember the logic level (LED ON or OFF) until next Clap/sound.

### Components

Condenser Mic

555 Timer IC

Transistor BC547

Resistors (1k, 47k, 100k ohm)

Capacitor (10uF)

IC7474 more precisely DM74S74N (D-type flip flop)

LED and Battery (5-9v)

### Circuit Diagram and Explanation

You can see the connections in above "clap on clap off circuit diagram". Initially the transistor is in OFF state because there is not enough (0.7v) base-emitter voltage to turn it ON.  And the point A is at high potential, and point A is connected to Trigger pin 2 of 555 IC, as a result Trigger pin 2 is also at high potential. As we know that, to trigger the 555 IC through Trigger PIN 2, the voltage of the PIN 2 must be below Vcc/3. So at this stage no output at OUT PIN 3, means no clock pulse for D-type Flip-flop (IC 7474), thereby no response from D-type Flip-flop, and so LED is OFF.

Now when we produce some sound near condenser mic, this sound will be converted into electrical energy and it will raise the potential at the Base, which will turn the Transistor ON. As soon as the transistor becomes ON, the potential at Point A would become low and it will trigger the 555 IC because of the low voltage (below Vcc/3) at Trigger Pin 2. So the output PIN3 will be high and a positive clock pulse will be applied to D-type Flip-flop, which makes Flip-flop to respond and LED will turn ON. This SET state of flip flop will remain as it is until the next clock pulse (next Clap). Detailed working of D-type Flip-flop has been given below.

Here we are using 555 timer IC in Monostable Mode, whose output (PIN 3 of 555 IC) has been used as a clock pulse for D-type Flip-flop. So the clock pulse will be HIGH for 1.1xR1xC1 seconds and then it would become LOW. You can learn 555 IC operations through some 555 timer circuits HERE.

### Working of D-type Flip-flop

Here we are using Positive Edge Triggered D-type flip-flop, which means this flip flop only responds when clock pulse would go from LOW to HIGH. OUTPUT Q will be shown according to state of INPUT D, at the time of the Clock pulse transition (Low to High). Flip flop remembers this OUTPUT state Q (Either HIGH or LOW), until the next positive clock pulse (Low to High). And again shows the OUPUT Q, according to the input state D, at the time of clock pulse transition (LOW to HIGH)

D-type Flip-flop is basically the advanced version of S-R flipflop. In S-R flipflop, the S=0 and R=0 is forbidden, because it is making the flip-flop behaving unexpectedly. This problem is resolved in D-type Flip-flop, by adding a Inverter between both the inputs (see the diagram) and the second input is given by the Clock pulse to both the NAND gates. Inverter is introduced to avoid same logic levels at both the inputs, so that “S=0 and R=0” condition never occurs.

D-type Flip-flop doesn’t change its state while clock pulse is low, because it gives the output logic level “1” at NAND gates A and B, which is the input for NAND gates X and Y. And when both the inputs are 1 for NAND gates X and Y, then output don’t change (remember S-R flip-flop). The conclusion is that it will not change its state while clockpulse is LOW, regardless of INPUT D. It only change when there is transition in Clock pulse from LOW to HIGH. It won’t change during the HIGH and LOW period. We can deduce the truth table for this D-Flip-flop:

 Clk D Q Q' Description ↓ » 0 X Q Q' Memory no change ↑ » 1 0 0 1 Reset Q » 0 ↑ » 1 1 1 0 Set Q » 1

### IC 7474

We have used IC DM74S74N of 7474 series. IC DM74S74N is the Dual D-type Flip-flop IC, in which there are two D-type Flip-flops, which can be either used individually or as a master-slave toggle combination. We are using one D-type Flip-flop in our circuit. Pins for first D flip-flop are the left side and for second flip flop are at right side. Also there are PRE and CLR pins for both the D-type Flip-flops which are active-low pins. These pin used to SET or RESET the D-type Flip-flop respectively, regardless of INPUT D and Clock. We have connected both to Vcc to make them inactive.

After understanding the D-type Flip-flop and IC DM74S74N, we can easily understand the use of D-type Flip-flop in our circuit. When we first triggered the 555 IC by first Clap, the LED glows as we get Q=1 and Q’=0. And it will remain ON until the next trigger or next positive clock pulse (LOW to HIGH). We have connected Q’ to to INPUT D, so when LED is glowing, Q’=0 is waiting for Second Clock pulse, so that it can be applied to the INPUT D and makes Q=0 and Q’=1, which in turns TURN OFF the LED. Now Q’=1 is waiting for next clock pulse to make the LED turn ON by applying Q’=1 to INPUT D, and so on this process will continue.

To test this circuit you need to clap loudly as this small condenser mic don’t have long range. Or you can directly hit at the mic lightly (like I have done in the video).

### Some Important Points

• If circuit doesn’t works at first, then connect the CLR (PIN1 of IC DM74S74N) to the ground to RESET the flip-flop, then again connect to Vcc as shown in circuit.
• We can modify this circuit using Relay to control the Electronic devices (120/220V AC).
• Control PIN 5 of 555 Timer IC should be connected to Ground through a 0.01uF capacitor.
• We should use a 220 ohm resistor to connect LED.

Video

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### Related Content

• Francis Manalo
Sep 16, 2015

where is you R2 Resistor in your diagram?, because in the list of your resistors they are 4 resistor which is 1k, 10k, 47k, and 100k, so where is 10k or R2?

• Dryx
Oct 04, 2015

Can you send me a modified circuit for 220VAC? please.

• Jayant
Oct 06, 2015

To operate 220v appliances, you need to interface Relay in place of LED. Check this article for using Relay module. Basically you need to connect Input of Relay module (I/P) to the Q (5) output of D type flip flop.

• Dryx
Oct 07, 2015

Will this work if i use a 6V source?

• Dryx
Oct 13, 2015

How can i adjust the sensitivity of the microphone?

• Abhishek
Oct 22, 2015

By using the proper value of Pull-Up resistor with your Mic, refer datasheet. Or use variable resistor and try different values. Or use different Microphone.

• aniket saha
Oct 15, 2015

Can I use BC548 /BC 557 transistor in place of BC547

Oct 18, 2015

Yes you can use BC548. But don't use BC557 as it is a PNP transistor and we are using NPN here.

• usman
Oct 22, 2015

i used 74f74pc ic and im having problem , when i connect battery ,light gets onn and remain on what should i do ???

• usman
Oct 22, 2015

YOU LEFT PINS 8 , 9 , 10 ,11, 12, 13 OF DM74S74N

• Abhishek
Oct 22, 2015

Yes, we left those PINs as we are only using one D type Flip Flop (out of two) inside the IC. Please check the PIN diagram and description.

• usman
Oct 23, 2015

thank you abhishek for reply i really appreciate you , please let me know on more thing , i used f74f74pc ic . when i connect 9v battery so led(Red) remain onn , mean without any clap it gets on .. am i using wrong ic ???

• Zidane
Oct 29, 2015

I would like to do this but how could I make it so that it has more than one led, for example I want to clap 2 times then the 2nd led will turn and when I clap 3 times the 3rd led will turn on etc. Thanks

Nov 03, 2015

This particular circuit is quite complex to design. Either you need to use three mic at distance or you need to cut out the one mic after trigger. You should try to do this using Microcontroller, or use IC4017 but latter will increase the complexity. Share here if you achieve this.
Thanks

• petchu
Nov 24, 2015

Pls can I use 74Ls174 ic for my clap on clap off switch? If yes how can I connect to pins

Nov 28, 2015

Although 74LS174 consists six D-type Flip Flop but it doesn't have Q' (Q bar) at the output, which is required in this circuit to be fed back into D input. You can use 74LS174, but circuit need to be modified accordingly and may need to use a NOT gate at output Q to generate Q bar. Better use 74LS175, it has four D type Flip flop with both Q and Q bar.

• chupet
Aug 27, 2016

Yes because its an ic that you can use in the circuit and that is the alternate for that ic

• petchu
Nov 28, 2015

Thank u very much!!. Its now I understand what d flip flop ic is all about. But honestly maddy am still new to this system. So hw am I to create a nor gate. Or may be I shud go read about logic gates

• David
Dec 10, 2015

Hi, i made the same circuit as yours, same components, eneverything. My Flip Flop starts overheating when i connect de 1 with 4 and after VCC.

• Rashid Qureshi
Dec 12, 2015

It doesn't work...Can you pls tell me where to put R2. And do I have to do the following steps as you mentioned:
•Control PIN 5 of 555 Timer IC should be connected to Ground through a 0.01uF capacitor.
•We should use a 220 ohm resistor to connect LED.
Pls help. I am stuck after making the whole circuit.

Regards
Rashid Qureshi

• Perish Jimi
Dec 14, 2015

Where can we get this 7474 ic ?

• Abhishek
Dec 17, 2015

You can get it from local electronics market or can order online, the detail about the IC is explained in above comment.

• Shivu raj
Jan 08, 2016

i used MC74ACT74N ic and im having problem , when i connect battery ,light gets onn and remain on

• Abhishek
Jan 14, 2016

Check the datasheet of MC74ACT74N and do the connections accordingly. Then try using 10k pull up resistor for condenser mic. Also check all the above comments if they solve your problem.

• Patrick
Jan 23, 2016

Hi. I used 74LS74AP and the connections are the same as DM74S74N but my problem is when I connect the battery the LED is on and remains on even after I clap. Can you help me please? Thank you very much.

• Karina
Feb 03, 2016

Will this work without relay? And what is the cable at the picture(the unshown full pic) connect to?

Feb 08, 2016

its already without relay. I think you want to ask, that whether it will work with relay. Yes, you can interface Relay to control AC appliances like here Remote Controlled Light Switch. And this is a single cable, not connected anywhere, it is just banded, and the band has been cut in the image. Follow Circuit Diagram, instead of image.

• bruno
Feb 16, 2016

I made the same circuit like you with SN74S74N (same dataseet), when i connect to battery the led is off and when i clap led get on and remains on even after i clap again.

• Ashok
Feb 17, 2016

Hi. I am trying to do this circuit without D flip flop so I'm taking output directly from PIN3. But the circuit is not working. No value is changing on base of transistor when clap..

• bruno
Feb 22, 2016

• nick
Mar 02, 2016

I made the same circuit like you with SN74S74N (same dataseet), when i connect to battery the led is off and when i clap led get on and remains on even after i clap again. what should i do?

• Marcus Casas
Mar 16, 2016

I made the same circuit with DM74LS74AN. What changes can i do so that the circuit will work?

• Shamiul
Mar 24, 2016

will this work with a 12v source??

• Abhishek
Mar 28, 2016

yes, it should but better use 9v battery as shown or some 5v source.

• samuel
Apr 04, 2016

thanks alot , is there an equivalent of IC DM74S74N? coz i have searched for it and failed to get

• Shamiul
Apr 07, 2016

I want to use a 741 op-amplifier, beacause the elctret mic is not working properly so can you please give me the full circuit diagram after adding the op-am in the circuit. Thanks :)

• vishal
Apr 24, 2016

I used ic 74AC74PC, but the led remains "on" and does not respond to clap.

May 17, 2016

Check the datasheet of 74AC74PC and do the connections accordingly.

• Chris
May 09, 2016

Can I use a 2N3904 NPN Transistor instead of the BC547?

• Debanjan
May 21, 2016

Thanks 4 sharing the circuit. Its working fine. But mic is not working from distance. How it can be connected to house hold appliance

• Lena
Jun 11, 2016

Is it ponsible to include the remote control system in the circuit of the clap sound? If yes how should I do it?

• Deep
Jul 15, 2016

I guess S=0 and R=0 state is there in SR flipflop. The S=1 and R=1 state gives invalid results instead.

Jul 25, 2016

Do we have any specific condenser mic used for clap switch?

• MiDi
Jul 27, 2016

It works, but...
but it works in reversed way.
I mean that, when I clap, it turn off. then after 3 sec, it turn on again.
Please do some fix, mate !

• Leshi
Aug 10, 2016

Is it possible to use a cd4027be IC and can it be possible to use a 2n222 transistor instead.

• Abhishek
Aug 13, 2016

check its datasheet whether It have all the pins needed in the circuit.

• allen
Aug 10, 2016

how do we supply the clock pulse.and is it -ve edge trigered

• Abhishek
Aug 13, 2016

Clock Pulse is being supplied by 555 Timer IC here and its +ve edge triggered.

• talha
Aug 31, 2016

sir, can I use d type flip flop M74LS74P in this circuit???

• Md Subhan
Sep 11, 2016

I want to use this sweech in AC circuit to on/off my fan then how to use this sweech.

• Ankita
Sep 18, 2016

Which condenser mic is to be used?

• Lwin zaw lhyo
Oct 02, 2016

Plz help me
I have alredy made but When testing
when I clamp the sound The LED is turned On but when I clamp again the LED is not become completly off .Meaning that instead of it must trun off but LED get alittle supply voltage so the LED is lighting alittle in Off mode

• Anshul Bharti
Oct 12, 2016

What to do if I want clap on and off circuit to use for 220V aupply,i.e.how to connect relay?

• shah rukh
Oct 22, 2016

how to introduce the relay in this circuit?do you have a diagram for that?

• Junhui
Oct 24, 2016

My condenser mic isn't giving out any signal. Is there any specify condenser mic we have to use?

• Uzair Arif
Oct 31, 2016

Kindly can you please create a video with step by step instructions on how to create a clap on clap off switch. Email it on my email []

• Joshua
Nov 24, 2016

Is it okay to use SN74LS74N? And how do i introduce the relay on the circuit? Do i ned to parallel a diode between gnd and output on flipflop?

• ali
Dec 04, 2016

Can we use the ic 4017 for 7474

• SAVIO VINCENT
Jan 31, 2017

It worked

• irfan
Feb 04, 2017

hey, i have make a simulation on your circuit...but it is not working...the led does not turn on...are there any mistake on your circuit...Please reply ASAP

• Armaan
Mar 10, 2017

Instead of a condensor mic, can you use a loud speaker?

• Junaid Ahmed Khan
Mar 21, 2017

sir
I followed all the steps and did same as the circuit diagram and instructions. But its not working.
It will be better if you upload a video showing step by step.
Thanks.

• James
Mar 28, 2017

The data sheet for the D flip flop says the IC has a max voltage of 5.25 V. How does this work with a 9V source?

Mar 30, 2017

I have to snap 3-4 times as current flowing to the base of transistor i.e electrical impulses released by mic are too less!! what should I do?

• B
Jun 16, 2017

U can increase the sensitivity of the mic by connecting a 100 nF capacitor with the positive of the kick and the other end to theBase of the transister also connect 2 10 k ohm resister one from the capacitor to Vcc and the others from collector of the transister to Vcc ,also connect a 1m resister from the Base of the transister (i.e from one end of the capacitor) to the Vcc . And continue the output from the collector to ic 1 as shown above. It worked for me!

• Unpopular
Aug 21, 2018

• izati
May 03, 2017

how much volt this 10uF..?

• Amit
May 06, 2017

I did everyrhing as the circuit diagram 3 times but when i connect battery the led remains on and does not switch off even if i clap. The 7474 also becomes warm.

• Arun chaudhary
May 11, 2017

i made the circuit but the light is not being off after being on
once

• allwin
Jun 12, 2017

can I use ic 74ac74pc instead of ic Dm74s74n in this circuit

• Abhishek
Jul 05, 2017

Check if your IC has two D-type flip flop, if yes then you can use it.

• Aparna
Jun 30, 2017

I am using the same circuit. Its working fine with LED and Buzzer at the output. Now I am trying to drive a Motor through driver IC ULN2803. The Motor turns on but turns off immediately before receiving the second clap. Do I need to do anything different then this.The Motor is 6v Dc 100rpm Motor.

• macques
Jul 10, 2017

I connected the components as instructed but when I clap the led doesn't even turn on, what could be the possible reasons?

• midi
Jul 18, 2017

i follow all the step and use all the component that being mention,but the led light up already after a battery is being supply to the circuit. it does not required any clap. please help me. i need to do this for my final year project. any idea?

• Venkat sai
Oct 29, 2017

Sir can share Gcb board structure of above project

• vijesh
Nov 30, 2017

How can i use relay in this circute..pls help me

• vijesh
Dec 10, 2017

Can i connect relay???according to this circuit??pls replay...

• Aswinth Raj
Dec 11, 2017

Yes you can replace the LED with a relay driver circuit and control the relay

• vijesh
Dec 19, 2017

Which transistor can use for relay driver according to tis circuit