Introduction: Earthquake Detector

Picture of Earthquake Detector

I grew up in California, and have had the fortune of experiencing every major earthquake in this state since I was born. I love them and fear them at the same time! Earthquakes are exciting, but also mysterious. Living in such a seismically active state, there are earthquakes all the time that most people don't even feel! That is why I decided to build this Earthquake Detector

Step 1: Tools and Materials

Picture of Tools and Materials

(x2) 741 OpAmps (Radioshack Catalog #: 276-007)
(x1) 9V Relay (Radioshack Catalog #: 275-005)
(xvar) jumper wires (Radioshack Catalog #: 276-102)
(x2) Heavy duty 9V battery clips (Radioshack Catalog #: 270-324)
(x2) 9V batteries (Radioshack Catalog #: 23-866)
(x1) Prototyping PCB (Radioshack Catalog #: 276-170)
(x1) Piezo Buzzer (Radioshack Catalog #: 273-080)
(x1) 5K Ohm Potentiometer (Radioshack Catalog #: 271-1714)
(x1) Potentiometer cap (Radioshack Catalog #: 274-415)
(x1) 470 Ohm Resistor (Radioshack Catalog #: 271-1317)
(x1) 3" diameter acrylic tube
(x1) Magnet (Radioshack Catalog #: 64-1888)
(xvar) lamp-pull ball-chain

Soldering Iron
Wire Snips
Hot Glue Gun

I used a laser cutter to make my own personal enclosure, but one could easily modify a pre-made project enclosure to suit the needs of this project.

Step 2: Modify the 9V Relay

Picture of Modify the 9V Relay

The only part needed from the 9v Relay is the magnet coil, the rest of the pins are not needed.

I trimmed all of the leads off of the relay except the ones that attach to both ends of the coil. I then soldered wires from each of the leads from the coil.

The purpose of the magnet coil in this circuit is to detect when the hanging magnet from the cylinder passes over it. The magnet sways when the earth moves, triggering the piezo buzzer to sound, and the LED to illuminate.

Step 3: Create a Home for the 9V Relay.

Picture of Create a Home for the 9V Relay.

One of the many perks of using a laser cutter is being able to make precision housing for your project. Because I knew I was using a 3" acrylic tube to hang my magnet in, I knew that I could make a 2.95" circle with a relay-sized rectangle cut out of it to perfectly house my relay in the middle of the tube.

Using CorelDraw, I generated a series of files for the enclosure, and then used .3" thick acrylic sheets to make the housing.

The file has 6 sides, with holes for the piezo buzzer, LED, and the acrylic tube. It is attached to this step of the instructable.

After I had my laser-cut parts, I glued my relay into it's home in the round, that will later be inserted into the tube.

I placed the relay into it's nook, then hot-glued it into place. After it was in place, I soldered a wire from each of the leads.

Step 4: The Circuit

Picture of The Circuit

Here is the circuit diagram I used for this project. There is also a fritzing file attached.

Step 5: Connecting Two Batteries to the PCB

Picture of Connecting Two Batteries to the PCB

I used two Heavy Duty 9v Battery Clips.

I designated one ground rail, one 9v + rail, and another 9V - rail. I soldered the red positive wire from one battery clip to the top rail of the PCB, and took the black negative wire of the same clip and soldered it to the lower part of column 47. I soldered the other battery clip in by connecting the red positive wire next to the negative wire of the other clip, and the black wire to the clip of the bottom rail.

Step 6: Solder the 741 Op Amps

Picture of Solder the 741 Op Amps

I aligned the tops of the ICs with column 10 and 35 on the PCB, so that they were straddling the center divider of the board. I then soldered each IC into

Step 7: Pin 4 and 7

Picture of Pin 4 and 7

On each of the OpAmps, pin 4 goes to the -9V rail, and pin 7 goes to the +9V rail. I used jumper wires to connect the span between the pins and rails.

Step 8: Pin 6 to Pin 3, and Pin 3 to GND

Picture of Pin 6 to Pin 3, and Pin 3 to GND

The output pin on 741 OpAmp is pin 6. The OpAmp IC on the left will be outputting to pin 3 on the other IC. Pin 3 is Non-Inverted input of the OpAmp. Using a jumper wire, I connected pin 6 of the left chip, to pin 3 of the right chip.

This is essentially reading the shifting output of the magnetic coil inside the relay, and comparing it to a normalized value.

Pin 3 on the left opAmp IC gets connected to the grounded rail that was established in column 47 of the PCB.

Step 9: Solder the Relay .

Picture of Solder the Relay .

Solder the relay coil into pin 2 and pin 3 of the left IC. When the magnet coil is activated in the relay, this is how the circuit communicates that motion from the sensor.

Step 10: Potentiometer

Picture of Potentiometer

I wired the left pin of the potentiometer to 9V+, the right pin to 9V-, and the middle pin  to pin 2 of the riht OpAmp IC.

Step 11: Wire Buzzer and LED

Picture of Wire Buzzer and LED

I was able to sink the LED and Piezo buzzer into the enclosure the same way I sunk the 9V relay into the housing. I made sure it was flush with the outward-facing side, and then hot-glued it into place.

I ran a 470 Ohm resistor from the 9V+ rail, and connected that resistor to the positive lead of the LED. Both the LED and Piezo buzzer's negative lead run to the output pin (6) of the right IC.

Step 12: Assemble the Enclosure & Sink the Magnet to the Relay Coil Into the Tube.

Picture of Assemble the Enclosure & Sink the Magnet to the Relay Coil Into the Tube.

I built out the bottom of the enclosure, and then set in the lid with components attached to the bottom. I then ripped off all of the paper that was protecting the enclosure from oils and scratches

I punched a small hole in the lid of the acrylic tube with a nail, and then ran the lamp chain with a magnet hot-glued to it so that the magnet just hovered over the relay coil. You want to hang the magnet so that it almost touches, you can see that it wants to stick to the relay, but it doesn't actually magnetize to the component.

Step 13: Implementation

Picture of Implementation

A good way to test this circuit is by jumping on the ground, and adjusting the sensitivity potentiometer that way. You may have noticed that there is no power switch integrated into this design - this is so the device is always on, and so that one can always know when an earthquake is happening, even if you cannot feel it. (It will also tell you when trains, and big trucks are going by!)


sam127 (author)2017-11-07

can i use normal buzzer?

audreyobscura (author)sam1272017-11-07


Angielol (author)2017-08-19

Can i get the circuit diagram?thank you.we will just use it for our thesis thank you.i hope for your response

firda_intani (author)2016-04-18

can i use usual buzzer than piezo buzzer? i dont understand how piezo buzzer works in this

ink123 (author)2015-10-02

where to connect the two wires from the relay

myaccountsan (author)2015-07-30

what is the radar area it covers.

SantoshN4 (author)2015-07-26

Hi My name is narayana I am from INDIA ,i love to do this project can i order this from india please can any one help me .

EdzelZ (author)2015-07-17

whats the purpose of the magnet hanging and the coil??? plsss explain

DebbieP2 (author)2015-03-14

water in a glass with a magnifying glass over the top of the glass works just as well keeping an eye on the ripple vibrations. Not all vibrations are caused by small earth quakes of course. If you live near road traffic cars and trucks would keep this busy.

SabaS2 (author)2015-01-26

Where in the cap of the tube did you make a hole for the chain? is it in the center? or to the side? Thanks so much. such cool project!

thegrosskid (author)2015-01-10

What size wire do I use for everything???

I think I used 20 Gauge wire

Thanks, it works!!!!!

hemanrocks (author)2014-12-02

how much does it cost ?

john.bobadilla.7 (author)2014-10-18

thanks :) it works now.

john.bobadilla.7 (author)2014-10-18

thanks :) it works now.

john.bobadilla.7 (author)2014-10-18

thanks :) it works now.

john.bobadilla.7 (author)2014-10-18

thanks :) it works now.

john.bobadilla.7 (author)2014-10-09

Hi nice project. What if I use 6V relay.? what will happen? PLEASE REPLY. I copy your project.

should still work.

john.bobadilla.7 (author)2014-10-09

Hi nice project. What if I use 6V relay.? what will happen? PLEASE REPLY. I copy your project.

Elenapervez (author)2013-11-06

how can we add a sound alarm to it? PLEASE REPLY.i need to make this urgently!!

David97 (author)2012-12-12

I live in Christchurch, New Zealand. I wonder how sensitave this would be as we have just had an earthquake that caused us to loose water for 2 weeks and power for a month and killed 300. We are still getting aftershocks a day after 2 years!

Wareneutron (author)2012-11-05

nice work!

Attmos (author)2012-10-14

Every home in California should have one. ;)

static (author)2012-10-08

While not exactly the sme Forest Mimms II had a similar project in Science Probe. Simply used a wound coil, and had mineral oil to dampen the magnet movement. Also had an output that could go to a chart recorder or PC recorder software

Light_Lab (author)2012-09-29

If you want to focus on earthquake motions you probably want to detect the vertically moving primary waves. These have a frequency around 0.1 to 1 Hz.
The easiest way to do this is to have a fairly heavy weight on the end of a coil spring. This will increase the sensitivity to lower frequencies. The other thing to do is to have some sort of damper like a paddle in oil. This might reduce non-earthquake vibration detection like trucks and people walking around.
You could do some of this electronically with filters.

pfred2 (author)2012-09-25

We had an earthquake here last year. It sucked! When the Earth is moving there really isn't anything anyone can do about it now is there? It was really more like a wave here. I saw my garage floor come up, then sine wave fashion go back down again. I thought I was flipping out. I mean we're not known for having earthquakes in these parts. In any event the feeling of helplessness I felt was palpable. I like my terra firma!

audreyobscura (author)pfred22012-09-28

Agreed. I have been on the west coast my whole life, and have grown accustomed to earthquakes, I have noticed that my best earthquake detector is my dog - she goes and sits in my closet maybe 20 minutes before there is one.

couldnt you use a reed switch instead?

ppsailor (author)2012-09-27

Years ago I built a motion sensor similar to the samples we.
Can you please show the circuit diagram clearer? FULL
To compare it with mine

audreyobscura (author)ppsailor2012-09-28

Circuit Diagram is now the main image for step 4.

ferjanyen (author)2012-09-28

Hi, a very nice project!!! I live in Spain, Torrevieja,(an earthquake aerea) and I would live to make this project but I would also like to see the circuit diagram for this project,

audreyobscura (author)ferjanyen2012-09-28

Circuit Diagram is now the main image for step 4.

devalpha_1 (author)2012-09-28

Great Idea. Kindly provide the circuit diagram.

audreyobscura (author)devalpha_12012-09-28

Circuit Diagram is now the main image for step 4.

TechGnostic (author)2012-09-27

My first Earthquake experience was when I soaking was in the tub. I hope that image doesn't violate the "be nice" policy : ))

Anyway, I was just lounging and enjoying the feel of the water when I noticed the water started to slowly sway side to side! I wasn't moving at all, and I couldn't understand what was going on at first. Since I live in a tectonically "stable" part of the planet, it took a few seconds to hit me that it was an Earthquake - a very mild one.

Since then I've always wanted to build a detector / data collector.

Not sure if you have this already - here's a link the the USGS Earthquakes data pages

Thanks for some ideas on How-To.

AtomRat (author)2012-09-25

It's still great, can b used 4 many other things too! Ill still make one

AtomRat (author)2012-09-24

I have seen a different version of these where you can use the piezo buzzer as a mic to pick up the tremors, if you are interested, tell me and I'll find it for you, its an ebook ( like a '..For The Evil Genius' ebook collection. ) In the meantime, this one is much more simple, and I'll give it a go as I do need one at the moment for tremors that I swear can continue for days.

Is this kind of just a motion sensor 'switch', rather than a detector? Can you get a reading from this to log the strength of a quake / tremor, or is the relay just turning on an earthquake alarm for nearby people.

audreyobscura (author)AtomRat2012-09-24

It is more of an alarm. As long as the magnet is sweeping over the relay (triggered by the earth's motion), the buzzer will sound.

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