Sunday, April 26, 2009

Tank driving around in REDC 140!

The tank is currently responsive and driving around on the floor in our lab with wireless commands from the user. Test runs are recorded and will be up on YouTube soon. During these trials the responsiveness is being calibrated for the optimal turn and speed change, that is, remove any jerkiness during transitions.

Problems that occurred during fully operational tank control includes:
  • The H-bridges require at least 12 V to operate; our battery only supplied 9.6 V, so we replaced this power supply with a 21.6 V 1200 mAH cordless drill battery. This new battery was found at Big Lots for $20 with a free drill.
  • Noise from the motors disrupted the control signals. Filter capacitors were placed on all of the power rails to reduce this AC noise.
  • The pulse width modulated waveforms and direction signals from the MCU are passed through a restoring buffer. The waveforms are sent through two inverters, and the direction signals are inverted; this allows for a single hex inverter (74LS04) to accommodate all of these signals.
  • A TX wire from the user's MCU and the XBee was severed, disabling communication.

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