The article discusses a simple vibration detector meter circuit using a bar graph LED sequence for the level indications.
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.
How the Vibration Detector Circuit Works
The proposed circuit can be used 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 piezo electric transducer element.
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 force striking the piezo electric transducer generate tiny electrical pulses inside the transducer, 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 transducer 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.
The above circuit was successfully built by one of the keen readers of this blog, ADMIN. The following video was submitted by him which displays the practical working of his built prototype.
After some initial hiccups, Jason finally built his prototype of the above circuit, here's the video which he sent to me, let's all enjoy it:
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: