• 12/18/18

    stephen.mckay • 12/18/2018 at 22:50 • 0 comments

    Having finished the actual hands-on work for the project, we spent several hours creating our final report and attempting to find a way to perform an analytical calculation on our project. The difficulty arises in the fact that our circuit primarily functions in response to anomalies: smoke, heat, leakage current etc. 

    Finally, we prepared a short presentation for Thursday.

  • 12/15/18

    stephen.mckay • 12/15/2018 at 18:14 • 0 comments

    We continued to solder the third part of the circuit, which takes the 9V DC signal and converts it to a 1.7 kHz AC signal to feed into the transducer, onto the breadboard. Once we finished that, we wired up the transducer itself. We found that we had to create another ground line in order to ground the speaker. Finally, we glued a 9V battery socket onto the back of the breadboard and connected the power and ground leads to the power and ground lines on the top of the breadboard. (See image)

    At this point, all the components of our project are in place, and so we're testing the various parts of the circuit again to verify that it is working correctly. Both methods of detecting fire are operating as designed; however, the speaker turns out to be much quieter when wired in parallel with the other two sections of the circuit.

  • 12/14/18

    stephen.mckay • 12/14/2018 at 21:40 • 0 comments

    We continued to solder our circuit onto the final breadboard. We finished the heat-sensitive section of the fire detector, then moved on to the two relays and the AC source circuit for the loudspeaker. Our goal is to fit both relays, the transducer, and the three circuit sections on the same breadboard. We only succeeded in wiring up both relays, so tomorrow we plan to wire up the circuit which powers the transducer.

  • 12/13/18

    stephen.mckay • 12/13/2018 at 23:35 • 0 comments

    Began to test heat dependance of current through PNP resistor on separate circuit, using a heat gun to safely increase the temperature of the base lead and using a micrometer to measure current. One transistor was fried, but we used a backup and repeatedly checked it to ensure that it was still functioning. Up through 300 degrees Celsius, we saw no leakage current through the transistor. 

    We later determined that this was because we were only heating the base lead of the transistor, rather than the head of the transistor itself. Once we began heating the head, we were able to source up to a mA of current (at around 220 degrees Celsius. We successfully used the PNP Transistor in the circuit to switch the relay on by the application of heat.

    Next we tested the two audio transducers we have, and determined that one has a resonant frequency of about 1.8kHz, and the other has a resonant frequency of around 3.5kHz. Since we didn't have a power source that could produce an AC voltage at these frequencies, we built a small resonator circuit using 1 nF capacitors to generate a ~1.7 kHz frequency with the smaller transducer (see image). We plan to integrate this circuit into our final circuit board and use it to run the larger  speaker when either half of the circuit switches the relay on--when either smoke or heat is detected.

    Finally, we began to solder the LDR section of the circuit onto the final breadboard. We finished all the components up until the SPDT relay (second image).

  • 12/12/18

    stephen.mckay • 12/12/2018 at 21:39 • 0 comments

    Determined that transducer needs AC voltage, which we neglected to consider originally. We will probably use our homemade signal generator to function as the power source in the final circuit. Also tested the first part of the circuit (the section using the LDR as a smoke detector), which allowed us to verify that it is functioning properly, When bring light is shining directly on the LDR, the relay is turned off; but when the LDR is not illuminated, the relay allows current to flow.

    Then wired in the second half of the circuit (which uses the PNP transistor to detect heat) on the breadboard. In lab tomorrow we plan to begin soldering the parts together.

  • 12/10/18

    stephen.mckay • 12/10/2018 at 21:23 • 0 comments

    Gathered components (collected all except AC128 transistor). Began to design and lay out circuit on temporary breadboard. Finished ~80%  of light dependent sector of circuit on temporary breadboard and planned out steps for finishing circuit layout on Wednesday (12/12).