I created this Instructables in such a way that you can use the written instructions as well as the photos to follow along with the project.
DIFFICULTY: LOW - MEDIUM
TIME FRAME: Small weekend project.
PREREQUISITES: My instructions assume you know the basics of electronics and soldering. I don't explicitly go over how to solder but it may be a nice small project to introduce you to electronics.
Step 1: Parts, Materials, and Tools
A. Hummer Shake Flashlight (about $10 on eBay)
B. Universal Cassette Recorder Microphone (Catalog #: 33-3019)
C. Small 8 ohm Speaker (Catalog #: 273-092)
D. 8-pin Retention Contact (Catalog #: 276-1995)
E. LM386 Low Voltage Audio Power Amplifier (Catalog #: 276-1731)
F. PC Board (Catalog #: 276-150)
G. 220uF Electrolytic Capacitor (Catalog #: 272-1029)
H. 10uF Electrolytic Capacitor (Catalog #: 272-1013)
I. 10M ohm resistor (Catalog #: 271-1365)
J. 0.1uF Ceramic Capacitor (Catalog #: 272-135)
K. Plastic Cup
L. About 1.5' of wire, red and black each
M. 0.032" Rosin Core Solder (Catalog #: 64-009)
N. Electrical Tape or Duck Tape
A bit of corrugated cardboard (not pictured)
O. Wire Cutter / Stripper
P. Soldering Iron
Tin Snips (not pictured)
Scissors (not pictured)
Pen or pencil (not pictured)
Total Cost (assuming you have all the tools and materials, not parts): approx. $35
Note: Most of the parts can be commonly found at local RadioShack stores.
Step 2: Disassembling the Flashlight
1. Remove the bottom cap (the one with the wrist strap) from the flashlight by unscrewing it. (picture #2)
2. Remove the top cap along with the lens by unscrewing it. (picture #3)
3. Turn the flashlight over and remove the two screws using a small Phillips head screwdriver. (picture #4)
4. Now, remove the plastic cap previously held down by the two screws. Hold on to it though as we'll be putting it back very shortly. (picture #5)
5. Tilt the flashlight towards the LED end and the inside portion will slide right out. (picture #6)
6. Take the plastic cap you removed in mini-step 4 and screw it back into place at the bottom end of the flashlight. (picture #8)
7. Flip the flashlight over and use a small flat head screwdriver to pry the lens out. Once the lens has been released, remove it with your hand. (pictures #9 and #10)
What you have now is simply the inner core of the Hummer flashlight but this will be the canvas for the rest of the project. It also still works as a flashlight. Give it a try!
Step 3: Removing the Mic Element From the Microphone
The tool of choice in this step is the tin snips. If you don't have these already, you can purchase a pair from your local hardware store for about $10. Be sure to buy the ones with the yellow handles, this kind of tin snips allows for a straight cut.
Link to HomeDepot
Photo of the Tin Snips from Wikipedia
1. Clip the microphone wire and plastic end off using your tin snips. (picture #3)
2. Now that the end of the microphone is removed, stick the tip of one of the tin snip blades into the open end of the microphone and start cutting up along the side. (picture #4)
3. After taking a couple of snips, you'll notice that you'll start to hit some resistance because the blade of the tin snips can't go any further into the microphone cavity. Pull your snips out and cut perpendicular into the microphone, truncating it a little bit. Continue cutting along the side and truncating the microphone until you reach the microphone's switch. (picture #5)
4. Once you get to the switch, you'll be able to simply pull it out. A bunch of wires will be dangling. Snip the yellow and white wires as close to the switch as possible. (picture #6)
5. Continue cutting up the side, being especially careful not to cut the white or yellow wires. Stop cutting when you reach the top ridge of the plastic body. (picture #8)
6. Now, peel away the plastic body while holding the metal screen on top. You want to be careful not to damage the metal screen or any parts of the microphone element inside. (picture #9)
Good job! The microphone element you just removed will be the actual microphone piece in the final Shake Microphone.
Step 4: Prepare the Flashlight
Before I describe what to do, I just want to say that you have to be quite patient and gentle with this step. The circuit board you'll be working with isn't top quality, and you can easily tear the copper solder pads from the board if you push too hard or don't wait until the solder has liquefied. It can make things very difficult to work with if you manage to damage the board.
Alternate Step: By purchasing and using a solder sucker, removing the solder from the LED legs will be so much easier. But, it requires purchasing an extra tool from RadioShack. It's your choice whether you'd like to purchase the tool or not. It is quite useful if you plan on doing desoldering in the future.
RadioShack's Vacuum Desoldering Tool (Catalog #: 64-2098)
1. Start by pressing your soldering iron against one of the hard blobs of solder that hold the LED into place. Once the solder liquefies, take the tip of the soldering iron and use it to push one of the legs of the LED outward. Press the left one to the left and the right one to the right. (picture #1)
2. Use your wire cutters to snip the legs of the LED off and then pull the LED out from the top of the flashlight. (picture #2)
Step 5: Building the Circuit Board
1. Collect the following parts: (picture #1)
1 x 10M ohm Resistor
1 x LM386 Capacitor
1 x 8-pin IC Socket
1 x 0.1uF Ceramic Capacitor
1 x 220uF Electrolytic Capacitor
1 x 10uF Electrolytic Capacitor
1 x PC Board
2. Solder all the parts into place using pictures #2 and #3 as reference.
3. Using a wire cutter, pliers, snips, or even your hands, break off the extra PC board leaving about 1 or 2 holes of a margin around your circuit. (pictures #4 and #5)
Step 6: Connecting Everything Together
1. Let's begin by widening the holes where the LED legs used to go. The microphone will be placed into the cavity where the LED once was and the yellow and white wires will be run through the LED's holes. Use either the tip of your wire cutters or the tip of your Phillips head screwdriver, place it into the hole, then spin the tip in order to grind and enlarge the hole. (picture #1)
2. Hold the circuit board we previously completed onto the side of the flashlight, like shown in the picture below, to get an idea of how long your wires will need to be. We will now be adding wires from where the old LED used to be to your circuit board. About 4 inches of both black and red wire will probably do, though it's always better to have excess. (picture #2)
3. Cut your wire to length and begin soldering the red wire to the right pad and the black wire to the left pad. You may be able to use the solder that is already there to attach your wires. Be patient and be sure to heat up the solder and wire enough so that they stick together well. (picture #3)
(refer to picture #4 before moving on)
4. Cut a small strip of cardboard about 1/4" by 4-1/2". (picture #5)
5. Wrap the cardboard strip around your thumb to bend it into shape and stick it into the end of the flashlight. (picture #6)
6. First, wrap your red and black power wires around the flashlight push switch to get it out of the way. Second, feed the white and yellow wires of the microphone through the old LED holes. It doesn't matter which wire goes through which hole. Lastly, carefully squeeze the sides of the metal mesh inward in order to make the microphone fit into the top of the flashlight. Be careful not to hurt your fingers as the metal mesh can have sharp edges. (picture #7)
(refer to picture #8 before moving on)
7. Cut another piece of cardboard about 1" by 4-1/2". Wrap it around around the base of the speaker and use a piece of tape to hold it all together. (picture #9)
8. Using electrical tape or duck tape, attach the speaker to the bottom of the flashlight. I prefer electrical tape because it tends to look much nicer, but in this case, I only had duck tape available. (picture #10)
9. Solder the extra red and black wires to the corresponding speaker leads. (picture #11)
10. Attach the red power wire from the shake flashlight to the power rail on the circuit board, and attach the black ground wire from the shake flashlight to the ground rail on the circuit board. Looking at the back of the circuit board with pin 1 and 8 of the IC facing forward, the power rail is on the left in the center and the ground rail is on the right. Solder the wires into place. (picture #13)
11. Attach the red wire from the speaker to any hole directly adjacent to the ground leg of the 220uF capacitor, solder it to the ground leg of the capacitor. Attach the black wire from the speaker to the ground rail. Flip the circuit board over and solder them into place. (pictures #14 and #15)
12. Attach the white wire of the microphone to the rail shared with pin 4 of the IC. Attach the yellow wire of the microphone to the rail shared with the 0.1uF capacitor and the 10M ohm resistor. Flip the circuit board over and solder them into place. (pictures #16 and #17)
Congratulations! At this point you should actually have a fully functional Shake Microphone. Give it a try! Give the microphone a steady shake for about 10 seconds, press the button on the side of the flashlight and then speak into the microphone. If you hear your voice coming out of the other end, you'll know immediately that you did everything correctly. If for some reason you don't hear anything. Go back and check all your connections on the circuit board before moving on.
13. Take the plastic cup and place it top down. Put the speaker end of the flashlight onto the bottom of the cup and use a pen to trace the speaker. (picture #20)
14. Using an X-Acto blade, scissors, or even the wire cutter, cut the traced circle out of the plastic cup.
15. For the very last step, use electrical tape or duck tape to attach the plastic cup to the plastic ridge just above the speaker. (picture #21)
And that is all, you've just built yourself a Shake Mic! Just what you've always wanted too, a microphone that will never run out of batteries.
Step 7: Testing
1. Shake the microphone steadily for about 10 seconds. If this is the first time you've ever used the Shake Microphone or even its previous form as a flashlight, you'll need to shake it much longer. Once the large capacitor inside of the flashlight charges up a bit, it'll hold its charge and will require less shaking in the future.
2. Press the button on the side of the Shake Microphone. This button previously was used to discharge the large capacitor inside of the flashlight into the LED. Now, by pressing the button it will discharge the capacitor into the audio amplifier circuit.
3. Lastly, speak into the microphone at the very top. Your voice should come out amplified at the other end. You should be able to speak for about 20-30 seconds before your voice starts breaking up and the mic needs more shakes. That is all!
Step 8: Improvements + Notes
1. I've always found the LM386 amplifier to have poor sound quality. It may be how I've been making my circuits or the parts involved, but It would be nice to try and use a higher quality amplifier.
2. The speaker used in the Shake Mic is a very low wattage one. To be exact, it uses 0.1W. The LM386 circuit also allows a speaker with an impedance range of 8 - 30 ohms. So playing with a larger wattage speaker within that range could improve the loudness and sound quality. However, the higher wattage speaker you use will run the internal capacitor of the flashlight down faster.
Tip: Old computer systems equipped with internal PC sound often use 8 ohm speakers. This may be a good place to find a free speaker for testing. Low quality computer speakers can also be another device to look into.
3. I had originally used the Hummer shake flashlight because I found it in the trash still fully functional. I'm sure most shake flashlights would work for this project but my instructions are specific to the Hummer flashlight. If anyone is willing to use another shake flashlight and confirm that my Instructables worked for them, please message me and I'll create a table of compatible shake flashlights.
If anyone decides to improve the circuit, swap out the parts for improved ones, or has any tips on how to improve the electronics or even the Instructables, please feel free to send me a message.