In this write up we will discuss how to make a simple clap operated stairway light switch circuit for enabling a brief switch ON of the lights while the user crosses the lane, and thus save electricity.
Introduction
Stairways, corridors or small indoor passages often tend to be dark throughout the day irrespective of the outdoor ambient light conditions. Therefore keeping such passages illuminated all the the time becomes imperative, however this leads to unnecessary wastage of electricity.
An innovative way of solving this problem has been discussed in this article, by employing a clap operated momentary light switch circuit.
The circuit diagram may be understood as follows:
How the Clap operated Stairway Light Circuit Work
The idea is to switch ON the connected lights in the corridor through a clap sound, whenever the involved passage is utilized.
The clap sound triggers the circuit and keeps the connected lights switched ON for a few seconds or until the predetermined time is lapsed, after which the lights are automatically switched OFF.
The configuration is actually a transistor based clap switch, but without a flip flop stage, rather the flip flop is replaced by a delay OFF timer stage for the necessary switching and sustaining of the lights for a fixed predetermined period.
The stage as usual includes a sound sensor stage consisting of a mic and the subsequent transistor amplifier stage using a couple BC547 transistors.
The next stage consists of the PNP transistor BC557 which receives the signals amplified from the first stage via the 47uF capacitor.
The fed signals are further amplified to much greater levels for triggering the final LED driver stage.
The LED driver stage consists of a group of white LEDs which provides enough light for illuminating a small passage premise.
The two 39K resistors and the 220uF capacitors form the basic delay OFF timer and decides for how many seconds the driver stage remains ON with the LEDs lit.
The power to the circuit can be either applied by incorporating a standard transformer/bridge AC/DC adapter or if the circuit needs to be more compact, a transformerless power supply may be included with the below shown circuit.
All the NPN transistors are BC547B and the single PNP transistor is a BC557B, LEDs are ordinary 5mm high efficiency white LEDs.
The coil can be of any type, a 100mH choke will also do, it's introduced in order to keep the circuit stable and for avoiding self oscillations.
Anonymous says
Sir, how sensitive is this circuit?
Mez says
What are the 180E and 100E electrical devices?
Swagatam says
180 Ohms, 100 Ohms = resistors
Anonymous says
Hello, I have made this circuit but when I put batteries the LED's are glowing non stop. I'm claping but there is no effect. PLEASE HELP !
Swagatam says
Hello,
Please insert a coil at the shown position,in my prototype I had used the circuit exactly same as above and it worked wonderfully well.
For temporary testing you can use the primary (mains) winding of any step down transformer in place of the coil.
Stanislav Panteleev says
what does 32 swg means ?
Swagatam says
it's wire gauge or the thickness in SWG, equal to 0.2mm
Anonymous says
Sir Swagatam, What is the purpose of the coil in the circuit?
Swagatam says
It is to keep the circuit stable and free from external RF disturbances.
Anonymous says
how can we make the light last for longer? Please I need a fast response.
Swagatam says
you can do it by increasing the values of the upper 39K resistor or the 220uF/25V cap…or both.
Fahad Qureshi says
Sir what changes will made if i want to turn on 25watt bulb??
Swagatam says
connect a relay in place of the LEDs and wire the contacts with the bulb and mains.
akosimangaw meow says
sir is this working? tnx
Swagatam says
yes it's a tested design
Jack says
Hello. I was wondering about the coil. "The coil can be of any type, a 100mH choke will also do". Is the coil supposed to be 100 millihenrys? I'ts not very easy to get one around here, and I asked around, and with the "coil made by winding 100 turns of 32 swg copper wire on any ferrite core" instructions, people said it would not be even near 100 mH?
Thank you in advance.
Swagatam says
yes that's true, my data may be incorrect, the best way is to buy a ready made miniature choke as shown in the following links:
http://www.diytrade.com/china/pd/3364345/CHOKE_COILS_dip_inductor.html
Jack says
Thank you for your answer. Unfortunately the link you gave is not very informative. Could you post the henry value of the coil you used in your circuit? in millihenrys or microhenrys if possible so I wont get confused 🙂 If not, maybe just some approximate value that you would recommend.
Thanks again
Jack says
I forgot to mention that i've made the circuit, and been checking if it is like that one shown in the picture. I can't seem to find any other other obvious problems exept the coil.
Right now the leds are shining bright as day non stop. Could inserting a wrong coil have this effect?
Swagatam says
even without the coil, the LEDs should not remain lit continuously.
Without the BC557 conducting this can't happen, and there's no way BC557 can remain conducting because it's guarded by a capacitor at the base, which will allow only an AC trigger and block DC…the AC trigger can only happen when some sound its the mic……I have personally checked the design and it worked perfectly for me, although I checked it with a single LED across collector of BC557 and ground.
The coil is only for preventing spurious triggering.
so I am not sure regarding the exact issue with your circuit.
Jack says
Yeah it was my fault, obviously. Now the leds are not on all the time, but there is still some problems.
If we read the circuit from left to right, when I touch the collector of the second bc547 with oscilloscope, the leds light up and stay on for about 10 seconds as they should. The problem is that now I can't get the leds to light up with the signal from the mic. The signal goes all the way to the base of the second bc547 when looked at with oscilloscope, yet the leds wont light up.
Thanks again 🙂
Swagatam says
The mic has a polarity too, check if it's connected the right way round, because I cannot figure any other possible fault 🙂
Jack says
Been a while but i figured it would be nice to comment how it went. Basicly after checking the circuit many times, we figured out that removing the coil made the circuit working perfectly.
Good stuff you got here! Thanks!
Swagatam says
OK thanks!
Actually the coil data in incorrectly given in the diagram, actually it should be some 1000 turns of 36 SwG wire.
My prototype would get activated even with spurious external signals without the coil, and so I thought it was crucial there.