Gas station without pumps

2012 July 20

Cockroach electronics?

Filed under: Circuits course — gasstationwithoutpumps @ 23:01
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Another pair of bio-electronics labs that were suggested to me can be loosely described as Cockroach Electronics:

  • Cockroach Leg Mechanoreceptors
    The idea of this lab is to break off the leg of a cockroach, then use needle electrodes to measure the responses of various mechanoreceptors. I don’t think that this lab would go over well in Santa Cruz—dismembering cockroaches probably requires Institutional Review Board approval, even if it didn’t cause student protests. I don’t think that there is much more to this lab from an electronics standpoint than the EKG lab, and so I couldn’t justify dismembering cockroaches for it. If we were trying to teach about action potentials and mechanoreceptors in insects, there might be sufficient justification.
    It looks like the action potentials in their example traces are about ±100μV, so about 10× smaller than the EKG signals I was looking at, but the instrumentation amplifier design is essentially the same.
  • Remote-controlled Cockroach This one doesn’t harm the cockroaches, but steers them by exciting their antennae.  There is also a more detailed 3-page writeup in the latest Make magazine (Volume 31), but they don’t seem to have that one available in their “digital edition” yet (which would be hidden behind a paywall in any case).  Basically, they took the electronics out of the remote-controlled Hexbug Inchworm, and added a TI 551 chip (a low-power version of the classic 555 timer chip) to produce 55 Hz pulses from the DC outputs that went to the Hexbug’s motors.  By AC-coupling  the 55Hz signals via silver wires to the inside of the cockroach antennas, they were able to control the movements of the cockroach somewhat.

Despite the “coolness” factor of cockroach electronics, I don’t want to set up a breeding colony of giant cockroaches for this course, so we won’t be doing either of these labs.



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