Day of Making

My students were inspired by the Goldiblox video and are now working furiously on their own Rube Goldberg machine.  We should be finishing their Arduino projects, but whatever.  So they wanted to begin the machine with some way to complete a circuit, which would start a motor.  Their idea was to use salt water.  So, we rigged everything up, testing just the basic circuit, which we ran through an Arduino (which we didn’t need to but it’s cool).  The basic circuit worked, so we took it apart and set up the water.  We got salt from the senior lounge (I don’t want to know).  We ran the circuit again, flipped the switch, and . . . nothing.  We switch the ground and power wires just in case we had them backwards and . . . nothing.  So we stood around with our hands on our hips and then I suggested, based on my vast knowledge of electronics, that perhaps there was too much resistance so that there was power, but not enough for the motor.  I didn’t have a voltage meter handy, so we decided to try an LED, which doesn’t need much power.  And, it worked!  But, it also proved that we couldn’t power the motor, so we had to come up with an alternative.  And so we turned to metal.  We were scheming to borrow copper from the jewelry teacher when I decided to try some of the VEX metal we had lying around.  We made a makeshift seesaw, tilted the metal to touch the other metal, and voila! the motor spun.  Below are pictures of our attempts and a video of the metallic success.  Crazy, but fun day!

Design for circuit
Design for ending
Trying the salt water circuit with the motor
Salt water circuit working with LED


2 Replies to “Day of Making”

  1. If you want to keep the salt water, do it as an input to the Arduino. Configure a pin as an input with a pullup resistor, then put a wire from that pin and a wire from ground as the electrodes to detect the salt water.

    When the salt water is there the pin will read as 0, when it isn’t the pin will read as 1.

    Read the pin and control the motor with an output pin.

  2. I might try that, although now the girls are excited about driving a robot down a metal ramp, so we’ll see where we end up. We only have a week!

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