The shop shutter guard circuit discussed here guards your shop when its shutter is closed i.e., at night if an intruder tries to break the shutter, the piezo senses the vibration and the relay is fired to which a 230 volt bulb can be connected which makes the intruder think that someone’s inside.....but he doesn’t know he’s fooled by you!
You can also use this circuit for various applications like shock sensor or you can install it in your home to sense the door knock and buzzer rings( if buzzer is connected to circuit ) . It can also be used for automobile safeguard purpose. . .
CIRCUIT DESCRIPTION:
The circuit uses a piezo electric sensor to detect the vibrations. Usually piezos produce a voltage from few millivolts to 1 volt.
However, this voltage cannot have any use for our purpose. It have to be further amplified. So the four transistors are used here to amplify this voltage.
The amplified signal is fed to the pin2 of IC555 as trigger input. It in turn makes the output of the IC i.e., pin 3 of IC and this fires the relay and the buzzer(optional).
The output of the IC remains high for a preset time and after that time period, the output goes low and the relay and buzzer are turned off.
This time period can be varied by reducing or increasing the value of capacitor that is at pin6,7 and negative pole of DC source.
A 220uf (micro farads) capacitor can be used here. Its value may be varied to get desired timing interval.
The sensitivity of the circuit can be adjusted using the 2M preset. Take caution while soldering piezo as it is sensitive.
The shop shutter guard circuit works on any voltage from 6-12v but don’t forget to use the relay that matches with the voltage rating.
PLEASE REFER THE DIAGRAM OF PIEZO ELECTRIC SENSOR AND CONNECT THE MIDDLE WIRE OF PIEZO TO C1’s NEGATIVE AND OTHER WIRE OF PIEZO TO DC SOURCE NEGATIVE.
FIXING INSTRUCTIONS:
You can use a 0-12v transformer to power this up or in case of automobiles, connect this to the battery directly using a SWITCH to switch the circuit on and off.
And connect the car/bike’s horn to battery using relay contacts as a switch.
When someone moves the bike or tries to steal petrol or something from a bike, it senses the vibration and gives continuous horn for a predetermined fixed time, as set by the values of R5 and the series electrolytic capacitor.
You may use a buzzer instead if you don’t want to connect it to horn.
If you are using this for a shop shutter, you may connect relay contacts to a 230VAC bulb and fix the bulb outside the shutter.
You can assemble the circuit and enclose it in a plastic casing with holes for the sensor and power supply wires to reach the circuit.
Circuit Diagram
Written and Submitted by: SS kopparthy
PARTS LIST:
- IC-NE555,
- R1- 2meg preset,
- R2- 10K,
- R3- 1K,
- R4- 10K,
- R5- 1Meg,
- R6- 470ohms,
- C1- 2.2uf, 35v,
- C2- 0.1uf,
- Q1, Q2, Q4- 2N4401,
- Q3- 2N4403,
- L1- red led,
- PZT1- piezo electric sensor,
- D1- 1N4148,
- Relay- (as per voltage of power supply),
- Power supply- 9v-12v.
Comments
Also Sir, can I use 10k on Q4 collector to positive instead of the 1Meg resistor? That is because if I do 3 consecutive taps, the circuit will stop working. Maybe the 100uF across Q4 and PIN2 is not discharging fast enough. I tried replacing the 1Meg with 10k and it worked well Sir. Or could I just put a resistor in parallel just like in the RC network of PIN4? I am working on this the whole day Sir. But I can sense that we are going to solve this Sir. Just a little more tweaking.
yes 10k will do…I purposely suggested 1M so that the alarm switches OFF for sometime and under no condition responds to quick and random sound vibrations.
Hello Sir!
Can I just use 47uF and 10k resistor in parallel? Because the 100k/100uF still is not short enough for a power on succession. The 100k/100uF takes about 6-8 seconds to discharge. while the 10k/47uF only takes 2 seconds to discharge. Can it be done Sir? Any harmful effect on the circuit if I lower that values? Thank you.
Hello bugoy, yes that will do, no issues….I have been suggesting arbitrarily selected values and therefore it might not be accurate.
Hello Sir!
Good morning. I really did not proceed with the buzzer test last night because it might disturb anybody of its loud noise. I can do it today Sir. I am now preparing my demonstration to you. For the meantime, may I ask what do you mean by R4/PIN6/2? It was in your previous message. As far as the schematic is concern, PIN2 is not connected in any way to PIN6/7. Please clarify. Thank you.
Bugoy, it was a mistake from me…it should have been R4/pin2….and not R4/pin6/2
Hello Sir!
I'm still working on it Sir. I have not connected the buzzer yet because it is too noisy and it is already evening here Sir. But I tried muffling it with my finger and testing the circuit, and it works Sir. Regarding the instant ON during power up, i am trying to experiment on different values of resistor and capacitor Sir. But in the end I used the 10K and 100uF as you previously mentioned. I Found out something puzzling. It works the first time I connected the RC network for PIN4. But succeeding ON and OFF will fail. Then when I disconnect the 10K resistor and re-plug it again on the breadboard, it works again, not turning ON when powered up. Another thing I found out is that if I waited long enough for power to be disconnected, and reconnect it again, it will work Sir. Maybe 10-15 seconds of disconnected power before the RC network of pin4 will be operational again.
Please enlighten me Sir. Thank you.
Hello Bugoy, connect a 100k resistor in parallel with the 100uF, this will allow discharging of the capacitor as soon as power is switched OFF. Presently it's not working quickly because the 100uF capacitor is not getting enough time to get discharged and return to its original state….adding a parallel 100k resistor will rectify the issue.
Hello Sir!
Good afternoon. I tried all your suggestions and found out several things. I put 1M resistor across Q4 collector and positive. A non-polarized capacitor (ceramic/mylar) dont work. But an electrolytic capacitor did. However, the polarity is the reverse. If i connect the negative lead of the cap to Q4 collector and positive lead to Q4/pin2 junction, it does not work. But if I reverse the cap (positive to Q4 and negative to Q4/pin2 junction), it did work. So far so good. Now will try to connect a buzzer if it serves its intended function and purpose. By the way Sir, I used a 100uF cap on Q4-R4/pin2 junction and 2uF on pin6/7 and negative. Will update you Sir.
Please see below set-up and video Sir:
i1284.photobucket.com/albums/a561/butchmillo/555_zpss2w69ve6.jpg
i1284.photobucket.com/albums/a561/butchmillo/piezo_zpsa1c7g9ng.jpg
vid1284.photobucket.com/albums/a561/butchmillo/2015-07-10-027_mobile720p_clipchamp.com_zpsb069wzm6.mp4
In your video the buzzer is not connected, I thought the capacitor was added to prevent the looping effect due to the buzzer sound vibrations…
The video does not show this crucial test result
a non-polar will also work….I am saying these just to make sure that readers may not learn the incorrect facts.
I am glad it's working for you presently Bugoy, but technically it's incorrect….the negative of the cap must connect with the Q4 collector and the positive lead with R4/pin6/2.
thanks for updating …keep up the good work.
Hello Sir!
The 10k resistor and 100uF cap on pin4 did not work Sir. The circuit still initially turns ON upon switching ON.
Hello Bugoy, I think there's something wrong with your 555 circuit, it's not responding to any modification.
disconnect the 10K from positive and connect it to ground…remove the 100uF capacitor and now check.
this should completely disable the 555 output…if still the output sounds would indicate a faulty 555 IC.
if it gets disabled then you can be sure that the 555 is OK, in that case you can reconnect the resistor with the positive but change the 10k with a 100K and also place the 100uF cap back with pin4 and ground…..now you can check the switch ON response.
Wow! you are really a guru in your field of expertise Sir. Will surely try it now. I am really excited. By the way Sir, if I use a polarized cap using your previous suggestion, where would its leads go? Positive and negative? Q4 collector? 555 pin#2? My things are ready now. Just waiting for your response. Thank you Sir.
It's my pleasure Bugoy! for a polarized cap the negative lead will go to the collector of Q4
Hello Sir!
How are you? Been raining here all day. Sir, is there a way that can be done such that if power is applied to the circuit, it will not go to ON state initially? What I want is, when power is applied, it should be in the OFF state rather than ON state. Because it is kind of annoying if the bike's horn sounds every time I flip the switch ON for the alarm.
Thank you Sir.
to rectify this you can connect the pin#4 of the IC with the positive through a 10k resistor, and also connect a capacitor from pin#4 to ground…a 100uF will do
Good Morning Sir!
How are you? I tried again the circuit on breadboard this morning. It does not function again Sir. But if I remove the capacitor modification and bring back to original circuit it works Sir.
alternatively you can try a different approach.
keep the circuit as shown in the diagram…….connect a transistor BC547 with its collector connected with Q4 base, emitter to ground and base to pin#3 of IC 555 via a 100k resistor. feedback loop will prevent the circuit from latching to its own alarm sound
God morning bugoy, it has to function.
separate the stages and confirm them individually…disconnect the capacitor from the Q4 collector and manually connect it to ground and see how the 555 outputs responds and for how long it keeps the output stays ON….this will confirm the working of the 555 monostable.
next, take a LED with a 1K resistor and connect across Q4 collector and positive….tap the piezo and check the LED response…it should light up brightly with each tap on the piezo.
once this is also confirmed, connect the stages for getting the final expected results.
a resistor 1M should be connected from Q4 to positive to ensure discharging of the capacitor otherwise the circuit will not respond repeatedly.
Hello Sir!
I just got home. If I use an electrolytic cap, what would be the polarity? I found out last night that a ceramic cap will not work. Also, is there a way that can be done such that if power is applied to the circuit, it will not go to ON state initially? What I want is, when power is applied, it should be in the OFF state rather than ON state. Because it is kind of annoying if the bike's horn sounds every time I flip the switch ON for the alarm.
Thank you Sir. I will be waiting for your response. For the meantime, I will prepare the breadboard on the table now.
Hello Bugoy, it does not matter whether it's a polar or non-polar, both will work equally well, but it's important that Q4 conducts properly otherwise the IC pin#2 may not respond correctly through a low value capacitor.
Using a higher value cap might ensure a quick triggering than a low value capacitor, so it can be tried.
Sir, can I attach two piezo sensor in parallel? So i could put one in front and another at the back of the bike's frame/chassis?
yes it can be done!
What I did Sir is, I taped the piezo face down on the table and put a small motor in the output of the 555. So that the motor will vibrate the table surface every time it triggers. It works sometimes but most of the time it does not. It does not trigger even if I tap the piezo sensor.
you must give some time to the capacitor which you connected at the collector of Q4 to discharge, because as per your requirement the circuit must not respond to rapid triggering….therefore if you tap consistently, if won't respond after this modification….also you can try increasing the value of of the 555 pin6/7 capacitor for acquiring longer activation of the load…
Hello Sir!
I just tried it now, something is wrong. Sometimes it works, sometimes it does not. I tried 0.1uF, 0.2uF, 0.47uF, 1uF. Why is that Sir?
Hello Bugoy, please remove the 1M resistor which I suggested from the collector of Q4 to positive. and check….
Hello Sir!
Wow that was a quick and easy modification. Will try it now Sir. I hope it would solve the issue. Thank you so much Sir. I will update you ASAP. Take care.
you are welcome Bugoy…wish you all the best
Hello Sir!
How are you Sir? I'm back. After many attepmts contemplating on what kind of alarm is really suitable for my precious motorcycle, now I finally came up with what I think to be almost perfectly the one I want. It is the one you featured here, the SHOP SHUTTER GUARD CIRCUIT. I tried assembling it on breadboard and I was amazed and satisfied with the result. Even a single clap could trigger the circuit. I just replaced the 100uF capacitor with a much lower value to decrease the ON time.
But Sir, I still have a very minor question/problem. Here's the scenario. I used the relay to activate the bike's horn. I set the circuit to the sensitivity that I prefer. A single slight tap to the bike would trigger it. Very good indeed! But then the problem arises. Since the piezo sensor is attached to the frame/chassis of the motorcycle, and it activates the horn for alarm sound, the sounding horn continuously triggers the circuit and going on in loops. Because the piezo sensor gets triggered again by the horn sound. My question Sir, is there a way to make the circuit activates for a predetermined time only? And immediately resets to standby status after the horn stops. In that way, another vibration/intrusion can be sensed again.
Thank you so much Sir. I very much appreciate your unparalleled knowledge and patience with me. I will be posting the project when finished.
I am good Bugoy, thanks!
you can rectify the issue by connecting a capacitor between the collector of Q4 and the junction of R4 and IC pin#2, the value of the cap can be anything between 0.1uF to 1uF
also make sure to connect a resistor from the collector of Q4 to the positive supply…the value of this resistor can be 1M
I would definately try this one…….I am back …..my exams are over……and I am currently working on PIEZO ELECTRIC SENSOR…….a different kind of circuit…..when finished would forward u the same…..Please give me some time for the Led propeller…..would be sending u soon……
sure Ajay, we'll wait for the updates.