Batty Ultrasound Generator

Last updated Sun Sep 10 17:53:40 EDT 2000

Schematic Diagram

diagram
eagle sch file*.
*Eagle is a layout editor from CADSoft, a freeware version is available (Win & Lin)

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)

diagram

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)

diagram

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)

diagram

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.

transducer photo