ElectrifyingStacks on stacks on stacks. Caps on caps on caps. Also, no breadboards. As rules of thumbs, signal lines are physically separate from power lines, and twisted pairs are used when possible to reduce inductive noise. Power lines and signal lines are separated upstream to reduce conductive noise. Unnecessary lengths of wires are shortened to reduce stray capacitance. |
TIVA Pin-Out
All functionality is achieved using control from the TIVA microcontroller. Pins are allocated based on alternate function, which include:
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Motor EncodersMotor encoders used per specifications from manufacturer: https://www.pololu.com/product/4761 Encoder ticks from OUTA are connected to input capture pins on the TIVA for both the left and the right motor. The OUTB ticks are used to determine motor direction via quadrature. |
Infrared DetectionInfrared light enters an NPN phototransistor, which is tied to 5V, to generate a current. An MCP6294 op-amp in a trans-resistive configuration converts the current into a voltage. The signal passes a high-pass filter to attenuate DC signals. The signal then enters a pair of gain stages, which when combined, offer a total gain of ~1000. Finally, the signal enters a comparator (LM339) with hysteresis to convert the signal into a digital high or low for microcontroller input. The input of each amplification is pulled to ground to stabilize the signal from external noise sources. Motor DriverTLE-5206-2 drivers are used to drive the motors for several reasons: 1. TLE5206-2 is a MOSFET-based driver. Compared to BJT-based drivers that have 1.2V emitter-collector drops, the voltage drop for TLE5206-2 with ~60 ohm motors and 500mH Rds(on) is ~0.12V. 2. At 14.4 V nominal voltage, the motors at peak operation can draw 240mA each, which is well below the 5A continuous current limit of the TL5206-2. Power DistributionTwo 7.2V NiMH batteries deliver a 7.2V and a 14.4V line to Business Bot. Each line can be toggled on/off through separate switches and monitored through LEDs. A 5A fuse prevents current overloads from breaking downstream circuits and components. The 7.2V terminal powers the TIVA directly, as well as linear and switching converters. The more stable 5V output of the linear converter drives the signal boards, while the less stable switching converter delivers 5V to the servo and electromagnets. The 14.4V terminal delivers power to the LED strips and motor drivers. |