DETECT EARTHQUAKES!
This page shows a different and better way to make the Stormwise Bucket Seismograph. Normally the antenna is suspended over a short stack of magnets, but in this version the stack of magnets is suspended and the antenna sits nearby. Greatly increased sensitivity is obtained using this design.
This version eleminates the need to align the antenna over the stack of magnets and eleminates any drag that might be produced by the connecting wires. The result is a purer waveform and greatly increased sensitivity.
In this version of the seismograph, the stack of magnets is used differently and is increased in length to 4.75 inches long (30 magnets). The stack of magnets is placed inside of a glass bottle which is suspended near the antenna which sits off to the side. The glass bottle is filled with dry sand for extra weight.
Step 1:Obtain some 1 inch diameter circular Ceramic Block Magnets from LOWES hardware store. These are Hillman brand part No # 542002, pack of 6 pieces. Lowes UPC bar code # 0823679984. You will need 5 packs of these ( about 3 dollars per pack ) which makes a total of 30 magnets.
Step 2:Obtain a glass bottle. We used a SNAPPLE brand peach tea bottle (available at Wal-Mart or other grocery store that sells the brand of tea) as it is the correct height (about 7 inches tall) and diameter (about 2.75 inches). Empty out the original contents of the bottle and then wash and dry the inside of the bottle. Remove the paper label from the bottle.
Step 3:Carefully open the packs of magnets and make sure they are clean on the flat surfaces. Carefully make a stack of magnets 4.75 inches long like shown above. Don't let the magnets snap together as they may break or shatter.
Step 4:Place the stack of magnets into the glass bottle after pouring about 1/4th inch of sand into the bottom of the bottle. Don't just drop the magnets into the bottle.
Dry beach sand is available at WAL-Mart craft isle, or LOWES hardware stores.
You will need to place the rope between the first magnet and the rest of the stack to assist in positioning the magnets in the center of the bottle. You will remove this later by pressing down on the magnets and pulling it out.
Pull on the rope while pressing down tightly with your finger on the magnets, and gently pull on the rope to remove the rope. Make sure the magnets don't move up or from the center position.
Make sure the magnets remain standing up centered in the bottle. You may have to press down on them with your finger while pouring the sand at first to keep them in position.
Step 5:Continue to pour dry sand into the bottle. Fill to near the top of the magnet stack.
Fill the bottle to the top with sand so the magnets are completely covered so that they can not move around.
Step 6:Drill a hole into the center of the metal screw on cap. The hole should be 3/16ths inch diameter.
Step 7:Thread a small nylon rope through the hole in the cap and tie a knot like shown.
Step 8:Screw the cap onto the bottle.
The finished full bottle should weigh around 2 pounds and 8 oz if you use a 4.75 inch tall stack of magnets.
Drill a 5/8ths inch hole directly above one side of the carrying handle of the bucket like shown in this photo. Do the same to the other side of the bucket. You will use this hole to slide a piece of CPVC plastic pipe to hang the magnet bottle on.
Drilling is easy with this flat type of drill bit. Drill it carefully. Do not ream it out, you want the CPVC pipe to fit tightly.
Slide a piece of CPVC pipe into the holes. The pipe should be about 13 inches long if your bucket is the same type as ours is. Cut the pipe to proper length so that about 1/4th inch sticks out on each side like shown when inserted in the holes. The bucket's handle should not catch on it when lifted.
Remove the CPVC pipe and drill a hole right in the center. The hole diameter is 3/16ths of an inch.
The CPVC pipe.
Step 9:Suspend the bottle 0.75 inch above the bottom of the center of the bucket with the CPVC pipe.
Step 10:Place the antenna standing up near the suspended bottle. The distance between the bottle and the antenna should be 0.75 inch.
If the bucket has a bowed bottom that makes the antenna not sit straight then use a 0.75 inch thick piece of wood to brace the antenna so it sits vertically next to the suspended bottle. The antenna should not move or vibrate. The only piece that moves in this seismograph is the suspended magnet bottle.
The resonant period of this seismograph turned out to be 1.03 Hz.
How it works: The antenna sits stationary near the suspended magnets in the weighted bottle. Upon seismic waves causing motion of the entire bucket assembly, including the antenna, the bottle tries to remain stationary due to principle of 'mass at rest stays at rest' effect. The rope will eventually couple the motion of the bucket to the bottle which will begin swinging like a pendulum. The moving magnetic field is detected by the ELF antenna and a current and voltage is sent to your recording equipment.
Pre-amplifier circuit design updated on October 3, 2013. This is the latest design update.
Uses common standard parts values, parts are available from Radio Shack or other electronic part stores.
Study all the photos and the above circuit diagram carefully. There is more than enough info on this page to aid you in a successful build that will work from the first try.
If your data logger instrument is not sensitive enough then you can add the extra gain required by using a simple two transistor pre amplifier.
This circuit is very sensitive and will allow detecting a 10000 gauss magnet (1 inch diameter 0.125 inch thick) at 15 feet away with the AF6T antenna, as an example of how sensitive it is. Any slight motion of the AF4T antenna over your magnet will register on your recorder.
Just want to detect the big quake that affects your area? Then don't use any magnet in your seismograph. The ground motion through earth's magnetic field will be enough for detection of (large) local ground motion.
If your chart recorder or oscilloscope is not sensitive enough on its own, then this simple two transistor pre-amplifier can be easily built from a few common parts from Radio Shack stores. This amplifier works from 0.03 Hz to 3 Hz, response drops off greatly above 5 Hz with parts values shown in list. Power drain is less than 1 milliamp at 9 volts for very long battery life.
Connect any logging millivolt meter or oscilloscope to the output of this pre-amplifier to see extremely slow waveforms. Use a data logging milliamp meter or data logging PC chart millivolt meter to record waveforms. See also www.dataq.com for PC data logging instruments. If you want to see clear seismic waveforms below 1 Hz you need a 13 bit resolution data logger. The 8 bit or 10 bit units make slow seismic waveforms look like static...
If using the DATAQ PC recording software, set sample rate at 20 samples per second. This gives excellent waveform resolution at 3 Hz and lower. Your seismograph should have a mechanical resonance below 1 Hz for long range sensing. To monitor only local quakes then you can use 2 Hz. Set chart scroll rate (chart compression) at 5 seconds per division.
Parts list: All parts are available from Radio Shack Stores, except for the Seismograph Antenna.
Parts list tested and optimised for both listed transistor parts.
Antenna: STORMWISE Part No AF6T-0.1H-1K-BC-EB or 8SR-1H-1K.
NOTE: If using smaller 8SR-1H-1K antenna then see parts value changes in parts list below to give the same sensitivity as the larger antenna AF6T.
2 and 1/8 inch Modular IC BREADBOARD SOCKET (base with holes circuit is built on) Radio Shack Catalog number 276-003.
JUMPER WIRE KIT: Radio Shack catalog number 276-173. Color coded wire kit for use with above socket.
IMPORTANT NOTE: Test each transistor's hFE value with a transistor tester, hFE gain value must be greater than 200, but not greater than 300. If greater than 300 then you will find that some transistor junction flicker noise (random ELF waves below 0.5 Hz) may be introduced by the transistor itself.
IMPORTANT NOTE: With the pre-amplifier circuit working and placed in a box to keep air currents off of the transistors, and the antenna connections shorted with a jumper wire you should see only a solid flat line on your screen or chart recorder. There should be no wiggles in the line when the antenna is shorted with a jumper. You should consider NPN transistors with hFE gains above 300 as 'defective' for use in this seismograph application.
NOTE: An inexpensive Multi-Test Meter (Radio Shack has these) can be used to test transistors, some models feature a transistor hFE gain test function.
Electrolytic capacitors have a voltage polarity marked on them. It is important to install them correctly or else circuit will not work.
NOTE: C3 and C5 limit the high frequency response of the circuit to below 10 Hz. They prevent power line hum from being detected. C1 pre-tunes the seismograph antenna to @ 6 Hz, and greatly reduces vibration noise of cars passing on roads, and vibrations above 10 Hz.
NOTE: The actual mechanical resonance period (not the electrical resonance of 6 Hz !) of the seismograph should be in the range of 0.5 Hz to 1 Hz for best performance. This mechanical frequency is controlled by how long of a rope you suspend the antenna with. A 18 inch rope gives @ 0.7 Hz, for example.
NOTE: If you pick up above 1 Hz (and if you don't need above 1 Hz), then change C1 to 47 uF or 100 uF. Don't use more than 100 uF across the input because loss of signal strength will result.
Question: What type of wire should I use to connect my antenna to my pre-amplifier? Answer: Use telephone wire (example: Radio Shack part # 278-367, a 100 foot spool).
Q1 = 2N3904 or 2N4401 NPN transistor.
Q2 = 2N3904 or 2N4401 NPN transistor.
D1 = 1N914 or 1N4148 silicon diode. (protects input transistor from negative static discharge). Wire polarity like shown.
D2 = 1N914 or 1N4148 silicon diode. (protects input transistor from positive static discharge). Wire polarity like shown.
R1 = 47 K-ohm resistor.
R2 = 2.2 K-ohm resistor. (1 K-ohms if using 8SR-1H-1K antenna).
R3 = 1 Meg-ohm resistor.
R4 = 47 K-ohm resistor. (33 K-ohms if using 8SR-1H-1K antenna).
R5 = 1 Meg-ohm resistor.
R6 = 10 K-ohm resistor.
R7 = 10 K-ohm resistor.
C1 = 22 uF electrolytic capacitor. Also see tuning info for the ELF antenna. (47 uF if using 8SR-1H-1K antenna).
C2 = 100 uF electrolytic capacitor.
C3 = 0.22 uF polyester film capacitor. (limits the high frequency response below 10 Hz by using negative feedback).
C4 = 47 uF electrolytic capacitor.
C5 = 0.22 uF polyester film capacitor. (limits the high frequency response below 10 Hz by using negative feedback).
C6 = 220 uF electrolytic capacitor.
C7 = 470 uF electrolytic capacitor. (Prevents scratchy contact noise from battery leads and random impulse noise from battery discharge process).
Click Here for More Photos of the Pre-amplifier.
Don't miss the small bare wire jumpers in the photo. One is near "G" (at the left in photo) and the other is just a few steps to the right just under the 100 uF capacitor.
Question: What type of wire should I use to connect my antenna to my pre-amplifier? Answer: Use telephone wire (example: Radio Shack part # 278-367, a 100 foot spool).
When first powered up, allow up to 3 minutes for the circuit to begin working and your data reading to stabilize. The capacitors need time to charge up fully, this takes about 3 minutes.
IMPORTANT NOTE: Test each transistor's hFE value with a transistor tester, hFE gain value must be greater than 200, but not greater than 300. If greater than 300 then you will find that some transistor junction flicker noise (random ELF waves below 0.5 Hz) may be introduced by the transistor itself.
IMPORTANT NOTE: With the pre-amplifier circuit working and placed in a box to keep air currents off of the transistors, and the antenna connections shorted with a jumper wire you should see only a solid flat line on your screen or chart recorder. There should be no wiggles in the line when the antenna is shorted with a jumper. You should consider NPN transistors with hFE gains above 300 as 'defective' for use in this seismograph application.
FINISH IT UP!
Notice how the binding posts are attached inside the box in the photo above. The (weak) lock washers that came with them were not used! Rather a stepped drill bit was used to drill the aluminum, which tends to melt it slightly during drilling. At first it will look like your're making a mess of the holes as it forms an ugly melted burr on the inside. Don't worry! When you bolt the binding post down to this ugly burr that forms it makes a built in lock washer in the aluminum box that holds far tighter than the one supplied with the binding posts. Just remember to drill the box from the outside else the burr will be on the outside instead of inside the box.
The only soldering needed is the wires on the binding posts, like shown. If you can't solder other methods are available for connections such as terminal posts.
We will be adding photos of the finished unit assembled into an aluminum project box (Radio Shack catalog number 270-238.
The unit MUST be enclosed in a project box of some type like shown above, to prevent thermal detection of room air currents blowing across the transistors. Try blowing on the transistors from 2 feet away, they will actually detect the sudden change of the air temperature from your breath. Enclosing the circuit in a sealed box completely stops this effect from happening. Slow normal room temperature changes do not affect the circuit when it is enclosed in a box.
This pre amplifier circuit will work with the DATAQ data logger at www.dataq.com or other data loggers which require a pre-amp for low level signals.
Too much sensitivity for your data logger? Change R2 to a higher value. Try 10 K-ohms to reduce level @ 5 times.
The Pre-Amplifier draws 0.73 milliamps at 9 volts. A pocket radio draws about 30 milliamps for comparison. A 9 volt NiMH battery will power the pre-amplifier for about 1 week before needing recharge.
For much longer run time you can use 6 "D" cell batteries, ( 9 volts total ) which will power it much longer than a small 9-volt NiMH battery. You can also use a 6-volt 4 amp-hour rechargeable "lantern" battery like the type used in deer feeders or in 6 volt emergency lighting. This type of rechargeable battery will power the unit for 2 months. Recharge the battery per the manufacturer's instructions with approved charger.
It has been observed that 9-volt NiMH batteries will quickly drop to a useless voltage level when needing to be recharged.
It is important to keep your battery fully charged as the output signal swing level (with this pre-amplifier shown) is dependant on battery voltage level. If you want to compare signal levels from different earthquakes you MUST have a stable battery voltage over time.
How to test the seismograph antenna from INDOORS without having to go outside and 'bump' it.
Below is an additional diagram showing how to wire a 10 K-ohm resistor and a momentary pushbutton switch. When pressed for about 2 seconds, it sends a tiny current through the seismic antenna which is suspended over the magnet. The weak field created by the current will push the antenna off center just slightly causing an effect that a real earthquake would do. You will need to make sure your magnet is positioned so that the antenna is repelled when the current flows and not attracted by it. The same magnetic poles repel, opposite magnetic poles attract. Use a compass to sense the magnetic field pole from antenna, then use the same magnet pole face up under the antenna in your seismograph. Current will push the antenna away from the magnet below it during a test.
Only send current through a 10 K-ohm resistor for the test.
RECORDING SOFTWARE AND HARDWARE from www.dataq.com.
DATAQ SOFTWARE AND HARDWARE (13 bit data resolution. Best unit, higher signal gain.)
DATAQ SOFTWARE AND HARDWARE (8 bit data resolution. Inexpensive PC data logger.)
Seismic waves have a frequency range between 0.3 Hz to 3 Hz. For best seismograph performance use the center of the band between 1 Hz to 1.5 Hz.
VIEW ALL EARTHQUAKES RECORDED WITH THE ANTENNAS
The very first earthquake recorded with the Bucket Seismograph # 2, occurred several hours after the installation. The glass bottle with magnet stack is shown in photos above. Antenna sits off to the side.
Magnitude 4.1 was 7 km S of Langston, Oklahoma on Feb 9, 2014 at time of 02:16:01 UTC.
Depth 4.8 km
The top seismogram is with a 6-inch (AF6T) antenna suspended over a 2 inch magnet in a different seismograph.
The bottom seismogram is the Bucket Seismograph # 2 with the AF4T antenna.
The Bucket Seismograph # 2 has higher sensitivity and better waveform resolution, in this one test, and the benefit of a smaller antenna. Notice how the wave shape is straight and not bowed down like in the top seismogram.
More earthquakes need to be recorded from different compass directions to compare the two methods (hanging antenna -vs- hanging weighted magnet).
Below are some larger images of the seismograms.
The second earthquake recorded with the Bucket Seismograph # 2, occurred 2 days after the installation. The bottom seismogram is recorded with the 'Bucket Seismograph # 2'.
Larger image:
Use our seismograph antenna model # AF4T-0.1H-40H-BC-EB and you can turn any 5-gallon plastic bucket into an earthquake detection sensor!
| Seismograph Antenna |
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Use this seismograph antenna to detect earthquakes. Detects both "P" and "S" waves from all directions.