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Home School Fun

Digital Seismograph

Ok so N.E.E.Week is mostly about conserving energy, and natural resources, we know and we understand.  This week is also for learning about our environment.  So when we were reading an article on earth quakes we thought wouldn’t it be cool if we could make one of those fancy meters that showed the ground moving? 

We watched a cool TV show on the BBC where scientist were placed in these remote areas of the world  with limited resources, and were given challenges to make tools and other items.  One show they had to build a seismometer, well they did not do a very good job (we didn’t think, so we started thinking about how we would do it…


A neat gadget that is readily available is the Piezo Electric Disc, it is a very simple device, a brass disk with a layer of quartz on one side.  When quartz is compressed it produces a small charge of electricity, so when you tap the Piezo disc you get a small amount of voltage.  If we could magnify this and measure it, we would have our Seismometer piece, of our seismograph (or our input).  So we began destroying McDonalds happy meal toys and “dollar store” play cell phones to harvest some discs. 

We were surprised at the voltage that we can produce by thumping these things.  Really cool, really high voltage, with low amperage, so you can feel it with out any real harm.  “Hey dave hold this wire for a sec” … “ouch!”  ha ha ha

As a side note: here is a schematic for the worlds simplest telegraph machine... 

Two Piezo Discs and a long piece of wire.  When you tap one of the discs it produces a spike of voltage which causes disc two to respond with a popping sound.  If only Samuel Morse could have seen this back in 1837!  LOL


Ok so we have our seismometer (sensor); we discovered if we add a large weight to the disc it becomes much more sensitive to sudden movements.  Enter the bolts and washers.  We glued (or rather JB Welded) a large bolt to the ceramic side of the disc.  Now with the added mass, all we have to do is tap the desk with our fist and we get a reading.  For added sensitivity we also added some heavy washers to the far end of the bolt. 


Next we have Connectivity.


Assortment of Piezo Discs.

When current is introduced the discs warp, and visa versa.

National Environmental Education Week

Date: 04/10/2009