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randofo (/member/randofo/)
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Bio: My name is Randy and I run the Autodesk Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to Make with a Dead Computer'. Since I am always making new things, subscribing ...read more » (/member/randofo/) More by randofo
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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
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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.
Using a sharp pair of scissors, trim your circuit board lengthwise so that only the center pads are left.
Note: You may want to use a dust mask while doing this, as circuit board dust is bad for you when inhaled. Cutting the board with scissors, greatly reduces, but does eliminate dust.
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.
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.
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.
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.
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.
(http://cdn.instructables.com/F7E/Q3DW/GOSDJJ6I/F7EQ3DWGOSDJJ6I.LARGE.jpg) 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).
Solder the red wire from the piezo to the signal wire of the cable.
(http://cdn.instructables.com/FPU/PVKY/GOSDJJ8Y/FPUPVKYGOSDJJ8Y.LARGE.jpg) 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.
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.
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.