The article discusses a couple of simple vibration detector meter circuits using transistors and also with an IC for getting a bar graph LED sequence for the level indications. The bar graph LED could be calibrated and used for measuring the strength of the vibration.
Introduction
Whether it's truck throttling over the highway, or an airplane roaring about the sky, or whether it's a knock on the door or a purring of the cat or simply your heartbeats, the vibration level detector circuit explained here will sense them all and convert into beautiful sequencing LED light bar graph indications.
The number of LEDs lit in the bar graph at any particular instant indicates the magnitude of the vibration force at that particular instant.
What is Vibration
Vibration is nothing but the ruffling of the air due a corresponding force generated from an external medium. For example when we speak, our vocal chords vibrate and generate the corresponding patterns of disturbance in the surrounding air.
When these air vibrations enter our ear, our eardrum also vibrate at the same frequency making it audible to our respective sensory organs.
Stronger vibrations make stronger impact on our senses and therefore we hear them louder in comparison to other sound levels.
The pitch of a vibration also becomes a major factor in determining their nature and strength. Pitch and frequency are probably the two factors which make a particular vibrating information more distinct with their technical specs.
As an example, a whistling sound may be shrill and might reach longer distances, but the grumbling sound from a mixer grinder even being much stronger won't reach across longer distances.
Though our ear is equipped with pretty impressive detecting capabilities, these organs cannot tell you the exact magnitude of a particular vibration force.
Using Transistors Only
The diagram shown above works very efficiently as a simple transistorized vibration sensor. It will sense even the slightest sound from the surrounding or the surface over which it is installed.
C2 allows a delay period for the relay so that the relay remains triggered ON for sometime on each detection. The value of C2 could be tweaked for getting the desired delay OFF on the relay operation.
The relay could be attached with an alarm system if the circuit is intended to be used like a vibration operated alarm or a door alarm etc.
Parts List
R1 = 4k7
R2 = 33k
R3 = 2M2
R4 = 22K
R5 = 470 OHMS
R6 = 4k7
C1 = 0.1uF
C2 = 4.7uF/25V
T1, T2 = BC547
T3 = BC557
D1 = 1N4007
Relay = coil voltage as per the supply voltage, and contact rating as per the load specs
Mic = electret condenser MIC.
Vibration Detector Circuit Working with LM3915
Another cool design can be built using IC LM3915 for detecting the strength of a particular vibration that might be emitted from some relevant source.
The circuit is basically a fun project, that may be built by a school kid and displayed in the school science fair exhibition.
The circuit diagram below shows a rather simple configuration using the versatile IC LM3915 from TEXAS INSTRUMENTS, which alone performs the function of sensing as well as displaying the vibration levels.
Pin #5 of the IC is the input which detects the variations in the induced sound via a electret microphone element.
A piezo transducer can be also tried instead of a mic. A piezo transducer element is a simple device used in piezo buzzers for emitting a sharp sound when connected to a frequency generator circuit.
However its being used for an opposite response here, that is for detecting a frequency rather than emitting it.
Sound vibration noise striking the MIC generate tiny electrical pulses inside the device, or rather the device converts all vibrations hitting its surface into small electrical signals varying in amplitude which corresponds to the strength of the striking vibrations.
These tiny electrical pulses from the MIC is effectively amplified and processed inside the IC LM3915 and the relevant sequencing LED display is generated across the outputs of the IC.
The LEDs connected at the outputs illuminate in randomly running patterns from the start point to the end point of the array, displaying the relevant information about the captured vibration signals.
This vibration detector or meter circuit can be further modified for more serious applications by including an alarm stage or a relay driver stage for triggering them in case a threatening level of vibrating force is detected.
The application may be user specified and therefore the present circuit might be configured or optimized in numerous different ways.
The IC needs negligible current and therefore a 9V PP3 battery would provide sufficient life to sustain the circuit, almost forever and also this makes the unit very portable and can be installed at any desired crevice or location.
Although the above proposed vibration meter/detector circuit was taken from the original datasheet, it has many flaws and won't produce satisfying results until some serious mods are done.
Recently when I tested it myself realized the drawbacks it possessed. The tested and modified diagram can be seen below:
Video Clip demonstrating the Vibration meter working
Parts List
R1 = 5k6
R2, R9 = 1K
R3 = 3M3
R4 = 33K
R5 = 330 OHMS
R6 = 2K2
R7 = 10K
R8 = 10K preset
C1 = 0.1uF
C2 = 100uF/25V
C3, C4 = 1uF/25V
T1, T2 = BC547
T3 = BC557
LEDs = RED 5mm type 20mA
Mic = electret condenser MIC.
angel acuña says
good morning me the same circuit can be used to measure the vibrations producidad for veiculo in db?
Swagatam says
yes it can be used to measure vibrations
Shinichi Kudo says
Hi Swagatam,
what about connected this circuit to your tachometer circuit (https://homemade-circuits.com/2012/05/make-this-simple-tachometer-circuit.html)?
Is it just replace the piezo to tacho-circuit output or need to add some additional components?
thanks
Swagatam says
Hi Shinichi,
connect the emitter of the transistor of the above circuit to the base of the tacho transistor directly.
Udayan Karmarkar says
Hey, swagatam could you tell me what sort of a piezoelectric transducer I should use? Also tell the manufacturer's name if possible
Swagatam says
Hi Uadyan,
Please see the image below:
www.tdpri.com/telephoto/data/500/piezos.jpg
Wowzaa33 says
For the vibration circuit, would it be possible to add an amplifier to the output of the piezo transducer to increase the sensitivity of the circuit?
I'm a paranormal investigator and having an adjustable, super sensitive vibration detector, would be a great help in my field. Geophones, while sensitive to the types of things we are trying to detect are a bit on the pricy side.
Any input would be appreciated.
Swagatam says
Yes it can be done simply by adding a transistor stage in between the piezo and the input of the circuit. In fact the sensitivity can be increase to any desired levels through simple modifications.
Wowzaa33 says
Thanks Swag! Is there a schematic for the transistor stage amplifier on your site? While I have taken high school electronics classes, it has been quite some time since then. SO at this point I'm back to being a newbie.
I have found your blog to be IMMENSELY helpful in some of my own endeavors in equipment design for the paranormal field. The LED drivers (and recent "surge protector" circuit) have been a God send.
Keep up the FANTASTIC work. I'm planning on making minor changes to vibration circuit. I'll post YouTube results for those that are interested.
Swagatam says
Thanks Wowzaa!!
You may try the following circuit with the above design:
https://homemade-circuits.com/2012/04/how-to-make-sound-activated-alarm.html
The output from T3 may be directly fed to the input of the IC.
I feel immensely pleased and satisfied when I see my readers benefiting from my articles, and that's what keeps me inspired to write more.
I truly appreciate your response. Thanks very much!
Jason says
I think it should be very basic and easy to do. Just a 555 timer to send a signal to a relay the relay then will open a pulse to a coil making a electromagnet field. Was thinking having an adjustable speed of the pulse from 2 times a second to 5 times a second.
Jason says
video of my finished project
www.youtube.com/watch?v=IjehOZRD0oE&feature=youtu.be
Jason says
Thanks for your help
next project it a pulsing electromagnetic field generator using a 555 timer chip.
If you have any ideas on how let me know.
Jason says
And I didn't change anything from last time must have been a bad chip
Jason says
I got it working really well. Any ideas on how to make it more sensitive?
admin says
Jason, I hot glued the piezo element to the bottom of my enclosure by drilling a small hole through the enclosure then applying the glue through the hole to the element beneath. This way the bottom surface was flat. I then added some additional weight to the inside of the enclosure directly to the top of the glued portion of the element. You have to play around with it to get the sensitivity your looking for. What surface you set the device on also affects how sensitive it is. Carpets, beds, towels, couches, work great over longer distances compared to wood floors, cement.
Jason says
I super glued mine inside the box as I will be taking around with me a lot. I am getting great detection on wood but everything else is not picking up well. I might try to use different resisters or even try using a larger piezo. I'm using a 35mm one atm.
Jason says
No idea why I just can't get this working. Will try to make it again today. Hopefully it was just a bad supplier of the chips I got.
admin says
Swagatam, awesome built mine today it works great, no changes were needed to be made to your schematic. Here is a video I made of it in action. This chip is very hardy, I mishandled it several different ways including, wiring it wrong. It still works like a charm.
tinypic.com/player.php?v=jtt508&s=6
Jason says
any chance of a pic of the complete on a bread board? Still having issues with this for some reason
Jason says
tried to build this and only the first led light up and the chip blew any ideas why? all connects match to above
Jason says
Do I need to use a resister for each LED?
and also the 2.2v to pin 3 does that come from a second battery?
Jason says
thanks a bunch swagatam.
what would I change to make the sensitivity adjustable?
admin says
I have a quick question, what type of leds, would work, (Forward Voltage and Mili Amps)and I am assuming they are all identical leds.