Hardware‎ > ‎The Critterbot Robot‎ > ‎

Electronics

The following are some notes and important information about the Critterbot's current electronics.

  • On the rev.1 sensor board the IR photodiodes are connected backwards.
  • On the rev.2 charger board, there is a silkscreen misprint.  R18 & R34 are swapped, and R1 & R6 are swapped. 
  • The differential line receivers are a major current draw (40mA, 45% of the power board's static consumption) NS-DS90C402?
  • D29 - MMSZ5251B-FDICT-ND is missing.
  • The chip select lines on the rev.2 board needs to be pulled high with a 10-100k resistor.
  • The charge enable lines should be held low by default.  This is a little complicated as they need a MOSFET to switch the pull between hard pull down and high impedance.
  • Check charger timeout resistors - set to timeout in 2 hours, in theory a fully drained battery may take more than 2 hours to charge to 1/10th C, which is the fast charge termination point.
  • Current path through a MOSFET body diode for batteries to system, this means the power board cannot be powered off.
  • Magnetometer gain is far too low, check amp resistor and update schematic to match board.
  • Need fuses/polyswitches on power entry to boards at minimum.
  • There is on-board temperature sensing for the walter PC104 computer.  Running 'sensors' will give you the current sensor temperatures, this is also logged to the system log.  This is useful information and should probably be inserted into the data packet.
  • The docking station current sense resistor is under spec and blew, causing the docking station to malfunction.  Required replacing U1, U2, and R11 on the docking station board, with digikey parts AD8212YRMZ-R7CT-ND, 296-13469-1-ND, and CSR1/20.025FICT-ND respectively.  The last part should be replaced with a higher rated sense resistor (1W or higher)

Comments