Lab 8

Blogsheet week 8

Rube Goldberg Take 2

Draw and explain a Rube Goldberg design that will include the following components:

·       Digital

·       Motor

·       Relay

·       Opamp

·       Temperature sensor

·       LED

The setup should be considered to last 30 seconds.

Make sure to include enough photos, videos, and explanations for each “transition” or step. Explain your circuits. Put at least 2 issues/problems/struggles you faced during the project.

          For our Rube Goldberg design we decided make a design that would pull a paper flag up a flagpole and, when the timing was right, break the circuit so the motor pulling both strings would stop.

         We kept the same design and setup for the week 7 lab which we didn't disassemble after we finished and added on an OpAmp, Temp sensor, relay, and a larger motor.  The reason we used another motor wasn't because we didn't have enough power to pull the flag or to pull the wire out of the bread board, but because it had 2 axels which could be more easily utilized to pull two things at once.

The drawing of our complete circuit, including values for resistors and voltage sources

               Once we decided what we wanted to do we pulled out our week 7 design and added the OpAmp, relay, temp sensor, transistor, and motor. 

Our set up near the beginning of the project.

         We decided that we wanted the design to be completely automatic once we had set it in motion, so we decided that we would use a domino like effect to land something on the pressure sensor to start the clock and begin the process of pulling up the flag.  Since we wanted it to be fully automatic we didn't use a heat source (though we decided we might have to if we wanted to speed it up in any way or if we needed to get more voltage to the motor) so we configured the OpAmp to produce enough voltage after the temp sensor to run the motor.  Once of our biggest struggles was figuring out which resistors to use with the OpAmp to produce the desired power and speed so we could reach the 30 second minimum. 

The next iteration of our machine before we decided on another arrangement. 

        For our XOR gate we used a constant input of 1 from the 5V source and then we used the A output from the display driver (alternating between 0 and 1 every second)  to give us the right timing.  The LED would turn on while the motor was running and would turn off when it wasn't.  This was another area where we had an issue, we found that any of the inputs (B, C, or D) from the display drivers that let the motor run for more than a second at a time was too fast for the 30 second threshold. 

        The video above shows our rearranged machine using C as the output of the display driver, it moves much too fast for the 30 second threshold so we needed to rethink the output that we were going to use. 

       Another challenge for our machine was that the motor had just enough power to turn at the speed we wanted, so any additional force on the string would cause the motor not to turn.  In the video below the motor doesn't turn, and the reason for that is that the "guide" for the string, so that it wouldn't fall off track and not wind around the motor, was catching.

      After this we changed the guides so that they wouldn't hamper the progress of the string so we could get the timing down without additional difficulties.  In the end we got it nearly to what we wanted, the video below is when we demonstrated it for the class.

A picture of our completed operation

Engineering Rules!