Tulley Family Tinkering Lab Website

More science fair news

by on Mar.08, 2010, under science fair

Robbie has completed the first part of his project — wiring up a K’NEX motor so that there are wires sticking out that will work as a switch. Then that is mounted to a light switch face-plate. (with holes drilled at a 45 degree angle in the bottom of the faceplate). We verified that the motor was strong enough to turn on the light switch like this, and that it took about 2 seconds to rotate one full rotation.

Next we found a circuit on the web (listed in the first entry about this), that showed how to use a 555 chip to create a 2 second signal whenever it gets a small signal as an input. ( http://www.ecelab.com/circuit-monostable-555.htm ) Robbie’s is very similar but with one more 555 chip circuit added in to make sure that the signal only comes out one time for every 20 or so beeps of his alarm. I had to teach him about logic gates to design this. Luckily we had an AND and a NAND gate chip, since RadioShack does not carry any of those.

Hopefully tomorrow he can put together this part of the circuit. Then the only thing left is the sound detection circuit. We have a few different examples of those on the Internet. One with 3 transistors, and the other with an op-amp. The op-amp uses the lowest amount of battery power, but I’m not sure how well you can adjust the noise sensitivity. He will probably just have to build it and see.

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