BEAM Pieces -- Integrated circuits - The Diigo Meta page

• 27 May 07
  

  York Jong

  1381s 34164s 5star 74x04 74x139 74x14 74x240 74x244 74x245 78M05 BEAM IC collection electronics robot survey

  • We use them as 3- or  5-volt triggers
  • 1381s are CMOS  voltage-controlled triggers -- these "gate" a source until  the voltage is above some "trip" limit, at which point it is  allowed onto a third pin
  • If you can't find 1381s locally, you might have better  luck finding its European cousin, the TC-54 -- for details  on it
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  • any *cores built with a 74*04 will require additional logic  "downstream" to amplify the current  to levels sufficient to drive a moto
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  • This chip is often considered the heart of Nv  net technology
  • Schmitt  triggers can't easily be used in suspended  bicore implementations
  • use its buffers as little current  amplifiers
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  • The '240 is often called "the bicore  chip," because we can take advantage of the 240's inverters  to turn a single 74*240 into a bicore
  • The '240 also has  tri-state outputs, so an enable line can be used to turn its  outputs on and off simply (good for adding reversing  capability to a 'bot).
  • it is usable for either grounded  or suspended  bicore  designs (but better for suspended)
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  • The '244 provides us with 8 (thus the "octal") buffers,  enableable in banks of 4. This is a very useful chip for  amplifying small currents
  • it can drive up to 4 motors in 2 directions  each, or you can "buddy up" inputs and outputs to drive  fewer motors at higher current
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  • The '245 is an octal buffer  chip, and so has 8 channels of buffering  power available for our misuse. This chip was designed for  data transmission uses, but we'll misuse it as a motor  driver chip
  • it can drive up to 4 motors  in 2 directions each, or you can "buddy up" inputs and  outputs to drive fewer motors at higher current
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  • Note that if you need more than  about 200 mA per motor, you'll need to use an H-bridge, or  some similar motor  driver
  • 74HC/HCTxx non-buffers  (74HC14 or 74HC04) draw about half of the current  consumption, and have about half the drive current  compared to HC / HCT buffer  chips (74HC240 or 74HC245). Non-buffer  chips are thus better for oscillators, say Nv  and Nu  applications; they are not suited for use in driving  motors.
  • The ideal BEAM  circuit would use a low (2V-3V) voltage core and sensors  combined with level shifting high (5-6V) volt motor  drivers to maximize efficiency.
  • 74ACxxx used in typical BEAM applications uses 4x more  supply current  than does 74HC/HCTxxx.
  • 74AC is best suited for motor driver  applications with all inputs driven rail to rail.

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Page Comments

• 
  York Jong on 2007-05-27
  The following material is intended to cover usage and part selection details of ICs you're most likely to see in BEAM robots.
  

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