Week 19 (Feb. 20, 2019): Component Testing & Programming

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Our Presentation #1 has been moved from next week – Wednesday, February 27, 2019 – to the following week – Wednesday, March 6, 2019, granting us a reprieve and permitting us more time to get more work done before the presentations.

We have been working on several things this past week.

David has been working on the Serial communication between the XBee on the Raspberry Pi and the XBee on the Arduino in the pod car. Specifically, he has been working on: acquiring a real-time location of each pod car, determining the distance between the passenger pick-up location and the closest pod car, and determining the distance between the passenger pick-up location and the passenger drop-off location.

This past week, Patrick has been working on getting the Electronic Speed Controller (ESC) to run the gimbal. Additionally, he has been working on a barebone circuit, consisting of the induction charger, the LiPo battery charger, and the 3.7V LiPo battery, and the motor. However, using the 3.7V battery will slightly lower the power provided to the Arduino, which is normally powered at 5V. As a side note: at 3.7V, the clock speed is approximately 16 MHz, while at 5V, the clock speed is approximately 20 MHz (http://www.gammon.com.au/forum/?id=11497). However, after some testing, the 3.7V battery can indeed power the Arduino and a 12V DC motor. This testing is being done before any soldering is completed and before a prototype is constructed, but soldering will definitely be done within the next week. While we don’t have to use the Texas Instruments buck converter-current amplifier IC anymore, we are still aiming to amplify the current up to 2A, or at least 1.5A.

This can be done by simply implementing a transistor. We will use a BJT NPN transistor, specifically the MJE270G Darlington Pair transistor, which has a maximum continuous collector current rating of 2A. The amplifier is intended to be placed between the induction charger receiver and the LiPo battery charger so as to increase the charge current, charging the LiPo battery faster. 



                       


Additionally, Patrick has been researching about voltage sensors that will know when the battery is running low on energy (voltage) and will alert the Arduino and the Raspberry Pi that it will return to one of the induction charging hubs to recharge the battery. A MOSFET could possibly be the solution, as the resistance between the drain and source pins is controlled by the voltage between the gate and source pins: if Vgs is below a certain threshold voltage, i.e. if Vgs < VTH, RDS is very high (open circuit), but if Vgs > VTH, RDS becomes very small (short circuit). Lastly, Patrick has been thinking of some ways to design the induction charging stations, such as a tunnel or a small pit stop.

  

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