The post details a simple sound activated relay switch circuit which can used as a module for any system that might be assigned to trigger by detecting some kind of sound pressure level.Or simply applications such as a sound activated alarm security circuit.
By: Arti singh gupta
Application Areas
Utilizing this sound activated switch, toggling a system by sound pulse could be very effective, not simply on a robot but as well as for some kind of home automation, as an illustration a sound-activated light bulb answering to a topple on the front door or a a hand clapping action.
The lighting is going to be promptly switched off after several seconds. An optional implementation is security protection system when someone aspires to break open the front door or ruin a thing, the light bulb may be expected to come ON on, indicating that someone uninvited is at your home.
The circuit could work from any 5-12 VDC controlled power source as long as a relay with the appropriate coil voltage is employed.
How the Circuit Works
As soon as you first associate the source voltage to the sound activated switch circuit, the relay will likely be energized on account of the impact of capacitor C2.
You must permit a couple of seconds for the relay to be flipped off. It is possible to maximize or minimize the ‘on’ time frame by modifying the uF C2.
A larger uF contributes to an extended ‘on’ span, and the opposite way round. However, you should not employ a value exceeding beyond 47μF.
Biasing resistor R1 establishes to a significant degree the microphone level of responsiveness. An electret microphone commonly possesses just one central FET inside which demands a bias voltage to run. The best possible bias degree for response to audio or noise level must have to be discovered by experimentation.
All of the related and useful electronic protection precautionary measures is required to be recognized each time while connecting mains powered loads to the relay contacts.
Parts List for the proposed sound activated relay switch circuit
R1 = 5k6
R2 = 47k
R3 = 3M3
R4 = 33K
R5 = 330 OHMS
R6 = 2K2
C1 = 0.1uF
C2 = 4.7uF/25V
T1, T2 = BC547
T3 = 2N2907
D1 = 1N4007
Relay = coil voltage as per the supply voltage, and contact rating as per the load specs
Mic = electret condenser MIC
HARSH SONI says
Will it work without relay?
Swag says
you can connect any preferred load in place of relay, it will work
Norman says
Hi Swagatam,
I think I figured it out. I increased the resistance of R1 and it is now more sensitive to sound. Your comments please.
Swag says
By changing the R1 value you have changed the MIC’s internal FET’s biasing level, so that might have caused the MIC to become a bit more responsive…you can also try increasing the C1 value and see if that helps to further improve the performance.
Norman says
Hi Swagatam,
I would like to make this circuit more sensitive. I removed the 4.7uF cap so it would follow music and flash a LED. It works but misses some of the sound, so I would like to make it more sensitive. Suggestions please. Thanks! Norman
Swag says
Hi Norman,
yes removing the 4.7uF cap will remove the latching function of the circuit and will allow instantaneous detection of the input vibrations.
Bubai says
Where to place an LDR to turn on a AC lamp at darkness only?
Swagatam says
this is not designed to work with an LDR
darz saludar says
0.1uF/25v?
Swagatam says
25V, 50V, 100V anyone will do
Sharoj Al Hasan says
ok….. sir i will try .. if stopped then plz help me
Swagatam says
OK
Sharoj Al Hasan says
Sir,
I want to make a Circuit which Can Active BY getting a siren Sound since 3 second Continiously …
And relay will Active For 30 Second….. sir please help me easily
It will very helpful for me
Swagatam says
then please do exactly as I have suggested in the previous comment…make the two referred deigns separately first and check them separately…
Sharoj Al Hasan says
Sir it will Very hard for me . i am basic Hobbist . Sir I want make a nice device with your kind help. i have a good idea . i want to tell you details then i think you will must help me.
So Sir how can i contact with you . and also i can discribe my idea to you.
Swagatam says
Please describe it here, I'll try to help
Sharoj Al Hasan says
Sir please help me
i want to modify this circuit. i want like this when, get a sound Continuously 3 seconds Then the relay will energized for 35 seconds . After 35 seconds relay will turn off Automatically. Everything will Reset
Swagatam says
Sharoj, you will have to add the following circuit with the above circuit
https://homemade-circuits.com/2013/02/make-this-simple-delay-on-circuit.html
remove the relay from the "sound activated relay" circuit and connect the T3 collector with R2 of the linked delay circuit.
make sure to remove R2 end from the positive.
Anonymous says
I want a setup where, when the dogs yap right next door, it turns on a circuit that immediately plays back their yapping at 10x volume.
Swagatam says
You can try a "speech jammer" circuit
Sharoj Al Hasan says
Sir How many Voltage For 100 uF Capacitor???
Swagatam says
16V or 25V
Sharoj Al Hasan says
Sir Actually I Want To tell you that
I want Make this System when This Circuit get a Sound Continuesly 2 Second Only then The will Start Working.
Swagatam says
for that you will need to connect a 100uF (approximate) capacitor across base and emitter of T3….
Sharoj Al Hasan says
Thank You Sir For Your Kind Reply.
When This Circuit Get Sound Since 2 or 3 Second Then The Relay Will On.
Sir please Help me
Swagatam says
yes the relay stay activated for 2, 3 seconds if the C2 is accordingly selected…
Sharoj Al Hasan says
Sir Please Let me know Sir
Sharoj Al Hasan says
Dear Sir
I want to Make A System.
I Want To Connect My Alarm Circuit Speaker Out Cable To Your Sound Active Relay On Circuit. When Get A Sound This Circuit Will Get On. My Mobile Speed Dail Number 1 is Connect With This Circuit relay. So when This Circuit get any alarm Then Relay will on. Thn My mobile genate a call . Now
Sir I Want To Remove My Mobile Microphone and Replace Mp3 out line on the point of my mobile Microphone
So Sir How Can i do this ???
Can u help me sir
Swagatam says
Dear Sharoj,
I am not sure about how to replace mobile mic with MP3 feed, you will have to consult this with an expert mobile phone technician…
Sharoj Al Hasan says
Hello Sir If Get Any Sound Relay Will Active. But For How many Second ??
How Can i Adjust This As my Wish??
And Sir Another Question Is
How Can I Remove My Phone Microphone And Replace 2 Mp3 out Cable Inthe place of My Mobile microphone
Thank You Sir
Swagatam says
Sharoj, yes it will be activated with any form of signal input…you can alter C2 value for the setting the time duration as per your requirement.
I am sure what exactly you are trying to do with your MP3 and cellphone mic….please clarify more for a better understanding.
Sharoj Al Hasan says
Yes Sir I Need mp3 sound active relay on Circuits. Sir basically I Want To Make An Circuit When this Circuit Get a signal From my Alarm Circuit this Circuit relay will on an i Want To Connect A phone Speed dail i mean 1 button with relay point. So when get a Sound I Will get a Call
Swagatam says
OK, then you can connect the junction of C1/R2 and the ground wires with the MP3 input…and the relay contacts configured with the phone speed dial button internally
Sharoj Al Hasan says
Sir Can I Remove The microphone And Replace Mp3 out at the point of Mic…. ????
Swagatam says
Sharoj, what's your requirement, is it to activate the relay using MP3 signal??
Unknown says
to avoid shattering , use Schmidt Trigger circuit
Bubai says
Sir,
How can I modify the circuit in such way that another similar sound or clap is required to turn off output (return relay NC position )
regarding your previous reply…
Shorting R6 with 10uF capacitor not behaving to eliminate Infrequent chattering effect.
Swagatam says
Bubai, if you are intending to build a clap switch circuit then you can build the second circuit from this article:
https://homemade-circuits.com/2011/12/make-simple-electronic-clap-switch.html
try connecting a 100uF parallel to D1, this will definitely solve the issue.
Bubai says
Thanks for posting such interesting circuit..
How to cancel Relay chattering effect ( some time happening) while returning NC position ?
How to increase or decrease sensitivity ( louder or low sound) triggering NO position?
Swagatam says
to stop chattering, try using a 10uF capacitor parallel to R6….
sensitivity can be increased to some extent by modifying (increasing) the value of C2
Nilesh Pachunkar says
nice sir..bahut badiya work krta he yr circuit
Chayan Mistry says
It's good
Mayank Padm Bhushan says
Sir ,
Very nice circuit i like this
Swagatam says
thanks Mayank!
Anonymous says
Sir,, I would like to know about your cellphone controlled car starter circuit ,,as I have done the complete circuit onto a project board,, I tried testing the circuit using 4.5v,,but I didn't get any results… Any suggestions on how I can test it before applying it on a car???
Swagatam says
please comment under the same article, I'll try to help