BAT SIMULATOR

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BAT SIMULATOR

• J. L. Errington

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BAT SIMULATOR

• To mimic a bat sound we need to have an
  ultrasonic output sound. This circuit gives a
  signal with a frequency of 45 KHz or 90 KHz
  repeating at a frequency of 8 Hz.
• The bat simulator used two NE555 timers. The
  component used for the practical circuit is a
  dual NE 555 called an NE 556.
• The first stage runs at 8Hz and controls the
  second stage that operates at 45kHz or 90 kHz
• The sound is produced by an ultrasonic piezo-
  transmitter

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Circuit diagram for bat simulator
9V
9V
1
14
2.2mF
1nF
2
NE556
13
3
12
4
11
39K
Piezo sounder
5
10
16K
16K
6
9
7
8
45 or 90KHz
8 Hz
F 1.44 / 2 R C Here R 16 K or 8K, C 1nF
Hence F 45KHz or 90KHz
F 1.44 / 2 R C Here R 39K, C 2.2mF Hence F
8Hz
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Circuit operation

• The high frequency part (LHS of the diagram, pins
  1 7) is controlled by the 1nF capacitor and 16K
  resistors.
• The low frequency part (RHS pins 8 14) controls
  the burst rate.
• The piezo sounder is driven very hard with a
  square wave and produces harmonics at 2, 3, 4 ..
  times the chosen frequency.

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Tested and working

• The circuit is built on veroboard and in a metal
  box to prevent electrical interference.
• A 10k resistor and LED have been added across the
  circuit to show when its switched on, and a
  switch in series with the battery to turn power
  on and off.

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FURTHER DEVELOPMENT

• The 1nF Cap could be increased to 4.7nF
• A 47K pot 4.7k series resistor would allow
  signals from about 8kHz to 80kHz (and harmonics
  to 160kHz) to be generated.
• A piezo tweeter would need to be used instead of
  the ultrasonic sender as they are not suitable
  for work below their fundamental frequency
  (45kHz.)