Electronic Stethoscope

An electronic stethoscope is an easy and fun listening device to make. It only requires some basic knowledge of electronics, and can be built with some basic easy to find parts. I have been having a great time using it to crack saf... I mean listen to my heartbeat. Yes! I have been having a great time listening to my inner workings.

Step 1: Go get stuff

You will need:

- 1-1/2" flat round cabinet knob
- LM386 Low Voltage Audio Power Amplifier (Model: LM386 | Catalog #: 276-1731)
- MPF102 Transistors (Model: MPF102 FET | Catalog #: 276-2062)
- 1K Ohm 1/4-Watt Carbon Film Resistor (Model: 271-1321 | Catalog #: 271-1321)
- 1M Ohm 1/4-Watt Carbon Film Resistor (Model: 271-1356 | Catalog #: 271-1356)
- 10 ohm 1/4W 5% Carbon Film Resistor (Model: 271-1301 | Catalog #: 271-1301)
- 4.7K Ohm 1/4-Watt Carbon Film Resistor (Model: 271-1330 | Catalog #: 271-1330)
- (x2) 0.047µF 50V 10% PC-Mount Capacitor (Model: 272-1068 | Catalog #: 272-1068)
- 220µF 35V 20% Radial-lead Electrolytic Capacitor (Model: 272-1029 | Catalog #: 272-1029)
- 100µF 35V 20% Radial-lead Electrolytic Capacitor (Model: 272-1028 | Catalog #: 272-1028)
- 0.1µF 50V Hi-Q Ceramic Disc Capacitor (Model: 272-135 | Catalog #: 272-135)
- Project Enclosure (3x2x1") (Model: 270-1801 | Catalog #: 270-1801)
- Multipurpose PC Board with 417 Holes (Model: 276-150 | Catalog #: 276-150)
- JVC® Gumy Earbuds (Model: HAF150B | Catalog #: 55042619)
- 10K-Ohm Linear-Taper Potentiometer (Model: 271-1715 | Catalog #: 271-1715)
- Hexagonal Control Knob (Model: 274-407 | Catalog #: 274-407)
- 1/8" Mono Panel-Mount Audio Jack (Model: 274-251 | Catalog #: 274-251)
- 6-Ft. Mono 1/8" Plug to Mono 1/8" Jack with Shielded Cable (Model: 42-2472 | Catalog #: 42-2472)
- Fully Insulated 9V Battery Snap Connectors (Model: 270-325 | Catalog #: 270-325)
- Enercell® Alkaline 9 Volt Battery (Model: 23-853 | Catalog #: 23-853)
- 90dB Piezo Pulse (Model: 273-066 | Catalog #: 273-066)

Comments

[jed6417]

Where do you wire the battery in circuit board?

[blinkyblinky]

Where the 9V is and where the GND is. All points going into 9V go to the positive and all points going to GND go to the positive part of the battery.

[abhieenriquez]

Can someone lend me a schematic? It will a great help. Thanks!

[pegawonder]

I am a novice interested in building one of these... Several of the parts are missing and I'm scared to order another piezo for example without understanding the impacts of different dB and electrical ratings. Any ideas anyone?

[i.saralynn]

Could this plug in to speakers?

[yungtiec]

How to wire the panel mount audio jack? Im still prototyping on breadboard and Im hopelessly stuck...

[acmefixer]

If this is going to be used for very low frequencies (that's the whole idea of a stethoscope), then the .047 uF between the 4.7k and 10k volume control should be replaced with a much larger capacitor, 1 uF or more. The positive end should go towards the 4.7k.

And since you already have a volume control, why not just replace the 1k between pins 1 and 8 with the 10uF capacitor recommended in the datasheet. BTW, even if you use the resistor, the datasheet still recommends using the 10uF capacitor in series with it.

[das007]

is there any equivalent of lm386. I do have lm380 can i use it.....?

[blinkyblinky]

I'm actually building this with LM358. It should work but make sure you use the correct pinouts.

[mat1978]

I'm so building this one :)

[siafulinux]

Nicely done!

[Polarize]

Great instructable :D nice video as well, although it would of been nice to see the stethoscope actually working :P