

Step 1: Go get stuff

You will need:

- 1-1/2" flat round cabinet knob

Step 2: Cut

Using a sharp pair of scissors, trim your circuit board lengthwise so that only the center pads are left.


Step 3: Build

Build the circuit tightly and as close to one side of the board as possible.

For now, don't worry about including the power switch, audio jack, potentiometer or piezo. These will be handled later.

Step 4: Trim

Once the bulk of your circuit has been built. Trim the board as small as possible in such a way that it won't interfere with the circuit itself, and remember to leave a few solder pads for the parts that you still need to connect.

Step 5: Mark and drill

Flip your case on its side. Make two _ _ _ marks _ _ _

Drill these marks using a 1/4" drill bit.

Step 6: Mark and drill again

On the two smallest sides of the case make centered marks.

Drill an 3/16" hole on the side closest to the other holes that you have just made.

Drill a 1/4" hole where the mark is on the opposite side of the case.

Step 7: Wires

With the potentiometer knob facing towards you, solder a black wire to the left potentiometer pin.

Solder red wire to the other two pins.

Step 8: More wires

Solder a red wire to the center toggle switch pin.

Solder the red wire from the 9V battery clip to either of the other pins.

Step 9: Some more wires

Attach a single red wire to the two pins on the bottom of the audio jack.

Attach a black wire to the ground pin on the side.

Step 10: Install

Install the potentiometer and toggle switch right next to each other inside the case.

Install the audio jack into the 1/4" hole on the opposite end of the case.

Step 11: Drill

Drill and 1/8" hole near the edge of the cabinet handle.

Step 12: Mount

For our purposes, the flat side of the cabinet handle will be considered the front.

Pass the red and black wires of the piezo through the hole you just drilled from front to back.

Epoxy the piezo to the cabinet handle such that the flat side of the piezo is facing out.

Be careful to leave a tiny bit of space between the cabinet handle and the solder points on the piezo (just in case the handle is conductive).

Step 13: Trim

Take your audio cable and cut a 3 foot section of cable out of it.

Don't worry about preserving the ends. We just need the shielded cable.

Step 14: Expose

Peel back the cable and twist together the shielding to form one single wire and expose the signal wire to form another.

Step 15: Attach

Solder the red wire from the piezo to the signal wire of the cable.

Solder the black wire to the cable's shielding.

Epoxy it all to the back of the cabinet handle in such a way that the solder joints won't make contact with either each other or the handle itself.

Step 16: Passing through

Pass the other end of the audio cable through the remaining hole in the case.

Tie a single knot to prevent it from passing back through.

Strip back the cable and separate the wires as you did in Step 14.

Step 17: Solder it all up

Complete the circuit as specified in the schematic.

Note that the audio cable's shielding goes to ground and that the center pin from the toggle switch goes to +9V.

The power switch goes between the red wire on the battery connector and the +9V in connection on the circuit board.

Step 18: Power

Plug in your 9V battery and install it inside the case.

If all has been done right, it should fit snugly.

Step 19: Case closed

Put the lid on the case and screw it shut.

Step 20: Knob

Attach your knob to the potentiometer.

Step 21:

Plug in your ear buds or headphones.

I used a pair of headphones and ear protection to make passive noise canceling headphones (jackhammer headphones).
<p>Is there any replacement for mpf102</p>
is this workng? or can i replace the piezo with a microphone??
<p>this project's piezo is not enough filtering. when we turn unit on i hear static and if i lightly tap the Piezo i <br>hear the tapping but i dont hear any heart beat, not sure what to do? Please send me new stethoscope new peoject</p>
<p>I do not think the Piezo is sensitive enough, if i was to use a microphone will this improve my chances of repairing this problem. Could someone please respond to my questions?</p>
How important is it to have a 90dB piezo pulse? How can I tell what type of Piezo pulse I have? <br>
hello <br>I have seen the draft electronic stethoscope and my really liked but I need to know how to calculate the value of the resistance and capacity of the circuit <br>thank you kindly answer me <br>I hope to answer as soon as possible <br>
Where do you wire the battery in circuit board?
Could this plug in to speakers? <br>
I'm so building this one :)
Nicely done!

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