Batty Ultrasound Generator

Schematic Diagram

Parts List

INTEGRATED CIRCUITS
-----------------------------------------------
IC1          Hex inverter
IC2          Quad AND gate (Dual would be best)
IC3          LM386 audio amplifier

RESISTORS
----------------------------------------------
R1, R3, R5   330 k
R2, R4, R6    56 k
R7             1 k
R8           2.2 k

CAPACITORS
----------------------------------------------
C1           150 pF   ceramic
C2             1 uF   electrolytic
C3            22 uF   electrolytic
C4           470 uF   electrolytic
C5           100 pF   ceramic
C6           470 uF   electrolytic

OTHER COMPONENTS
----------------------------------------------
SG1          Ultrasound transducer (emitter)
G1           9 V Battery

Notes

R7, R8 Voltage Divider:
R7 and R8 form a voltage divider that provides 5-5.5 V for the hex inverter
and AND gates.  The chips used here are CMOS technology and require a
lower voltage than the equivalent bipolar/TTL chips.
The LM386 amplifier, on the other hand, can use the full battery voltage.
The quad AND IC should really be a dual AND circuit, only 2 gates are used.


Calculated Time Constants:

                 seconds           cycles   
                   per              per
                  cycle            second
-----------------------------------------------
f1 = 2.2*R2*C1 = 0.0000185, 1/f1 = 54,500
f2 = 2.2*R4*C2 = 0.123,     1/f2 =      8.1
f3 = 2.2*R6*C3 = 2.71,      1/f3 =      0.37

The factor of 2.2 takes into account the approximate 80% swing needed for
CMOS logic gates to toggle.

Bells and Whistles:

The unit I built also has a red diode that blinks when ultrasound is being
emitted.  Helpful since one can't hear anything!

74HCT04 hex inverter


"The VHCT04A is an advanced high speed CMOS Inverter fabricated with silicon
gate CMOS technology. It achieves the high speed operation similar to
equivalent Bipolar Schottky TTL while maintaining the CMOS low power
dissipation.
The internal circuit is composed of 3 stages including buffer output,
which provide high noise immunity and stable output."


Fairchild 74VHCT04A.

datasheet (pdf)





74HCT08 Quad AND Gate


"The VHCT08A is an advanced high speed CMOS 2 Input AND Gate fabricated with
silicon gate CMOS technology. It achieves the high-speed operation similar to
equivalent Bipolar Schottky TTL while maintaining the CMOS low power
dissipation. 
The internal circuit is composed of 4 stages including buffer output,
which provide high noise immunity and stable output." 


Fairchild 74VHCT08A

datasheet (pdf)





LM386 audio amplifier


"The LM386 is a power amplifier designed for use in low voltage consumer
applications. The gain is internally set to 20 to keep external part count low,
but the addition of an external resistor and capacitor between pins 1 and 8
will increase the gain to any value up to 200."


National LM386

datasheet (pdf)





Ultrasound Emitter


RadioShack Cat.#: 900-6065 ($4.95)
A small 40 Khz ultrasound emitter (Velleman / MA40A5T).
The bandwith of these piezo-transducers has a narrow peak around 40 khz.
A group of students at UNN has measured it.