Here is how I do a simple piezo pickup
A trip to Radio Shack will get you the piezo and 1/4 inch mono jack. They are in a drawer case towards the back of the store and most stores usually have them in stock. The piezo you are looking for is the 273-073
and costs 2$ and the jacks are #274-255
and are two for 4 You can also pickup a 25 or 30 watt soldering iron and some fine(thin) rosin core solder here or go to Harbor freight and save some money. Its all chinese junk anyway. If you use a damp paper towel or sponge and keep the soldering iron tip clean it will last a fairly long time.
Keep it tinned (heat the tip and run some solder on it before soldering) Cheaper and easier to wear out a cheap iron and replace unless you're going into business. Do NOT tighten up the little screws on the barrel too tight as they hold the heating element in. Do not remove these screws and pull as it will junk the iron. (common mistake) Give the iron lots of time to heat up. It might take it ten or more minutes to come up to temp. This is normal for a low watt iron and you certainly don't need more watts. Too big an iron will burn the insulation off and melt plastic not to mention stink. Speaking of stink, ventilation is good as the fumes are not very healthy to breathe. (just a small fan blowing across you will do the trick)
If you go to Harbor Freight you can pickup a "helping hand" for only four bucks. (11$ at Radio Shack) and also save considerable on the solder and soldering iron.
Here are the URL'shttp://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47887
soldering iron 5$http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95861
Helping Hands 4$
The 273-073 piezo comes suspended in a plastic case as its original purpose is to be a buzzer. Since we want it to pickup the sound from our guitar and send it to our amplifier it needs to come out of the case. I have put together a picture story line to illustrate this. I take a pair of pliers and grasp the ear on one side of the case -squeeze and snap the ear and a piece of case off. You have two ears so two chances to get a good hole in the box to pry the top off with. I insert a pocket knife tip or small screwdriver in and slide it right under the plastic top so it misses the piezo completely - then pry the top up and it will pop right off. Careful the Piezo is suspended in there but its close to the top. Then stick a blunt small screw driver in the hole in the bottom of the case and gently push up. The piezo will pop right out with very light pressure. DO NOT BREAK IT by applying to much pressure. Easy does it. Now you can strip the insulation off the wire back a bit and twist the the strands into a single smooth wire. Insert it in the jack and twist it up tight so there is a half decent mechanical connection black goes to the center ring ground terminal on the jack and red goes to the lug that leads to the tall center pin part. Once twisted up tight plug the iron in and let it heat for ten or fifteen minutes. Tin the tip by melting a small amount of solder on it. Stick the tip in the hole on the jack and wait a few seconds then touch the solder to the tip where it came thru the hole and or to the wire itself. The tip heats up the parts to be soldered and then the solder "runs" up the wire and into the joint. If its done correctly it will all be silvery smooth and fairly quick. If the joint is not hot enough you will get a cold solder connection which is BAD. You do NOT melt the solder and drip it onto the wire or terminal. If the wire and terminal are hot enough the solder wicks up the wire as it melts - nice smooth and strong. Its not necessary to add wire to the ones I have built nor to put any switches in the circuit. I mount mine to the neck as it goes thru the box close to the bridge - I use foam mounting tape that sticks the brass side of the piezo to the neck - I use two pieces side by side to get it wide enough and then cover the top with two more pieces side by side to cover and buffer the piezo. This makes a nice clean installation and its extremely strong. Its also really buzz free. The foam mounting tape is double sided "Duck" brand 3/4 inch by 22 ft and 1.5 inches holds a quarter pound. Mounting the jack to the box typically makes me drill two holes - a larger one half way thru the box then a smaller one all the way thru. I have not had good luck keeping these tight enough yet and intend to use gel super glue liberally on the next installs to see if that will help.
When I get time I will put together another blog to illustrate how to double these piezos up reduce the impedance to closer to what a standard amp wants to see. Basically they are wired in parallel so that each set of leads goes back to the jack - so it would be a pair of reds and a pair of blacks coming back to the jack to use double piezos. Series doubles the impedance and parallel halves it. Parallel has a very desirable reduction in impedance. Another subject worth exploring is shielding the leads by wrapping copper foil around the wires and grounding back to the ground lug. This stuff is a bit tricky and care needs to be taken not to set up any ground loops. I need to take more pictures to correctly illustrate this.
Hope this all helps with any amateur soldering and piezo destructing. Comments and questions welcome - Bill
Fresh from Radio Shack, These are in a parts cabinet towards the back of the store. Piezos in one side and jacks in the other. Do not let the kids at radioshack BS you they don't know what is in the store. Almost always in stock. Look for them. 2$ each.
Piezo in plastic buzzer case also removed from case - brass side and ceramic side shown. This is what we want.
The one at the bottom of the picture is busted, I tried to solder the red positive wire back to the ceramic - overheated it and it broke. Probably not worth trying - these also do not bend !!
Grasp the case top and bottom on the edge right at an ear and twist a chunk off. The objective is to break a the edge of the case open so we can remove the top. (without breaking the piezo)
Just got a small bite - its enough though - I can get a screwdriver blade in there and if I needed to I could break the other ear off and get piece of the side too. Two chances to win this game.
Stick a narrow screwdriver or stiff knife blade in there right under the top and pop the top off. Stay close to the top so you don't bend the piezo. Its suspended down a smidge anyway.
And off pops the top. There is the piezo ceramic side up - brass side down. On the other side is a hole to let the buzzing sound out. Perfect to stick a small dowel or screwdriver in and nudge the piezo up. Gently!!
A gentle push up and there is the edge of the piezo, finger food now.
Another shot of the edge of the piezo up where it can be grabbed and the top removed.
The prize - a nice piezo transducer with leads factory soldered on . notice the red positive goes to the ceramic and the black ground goes to the brass base ring
Pair of 1/4 mono jacks - the center ring gets the black ground wire. The tall part contacts the long pin on the cord and it gets the red wire. Thats the left side terminal on the bottom jack.
Jack with leads from piezo soldered on . The black goes to the center ring - these solder joints are too large and would make an electronics tech sneer but they are well done and solid connections if not pretty. You can do this well with a minimum of practice. It works!
All soldered up and ready for a cigar box. No switch is necessary and the leads have been long enough for me to make them work every time so far. Simple down and dirty. There are better ways but no simpler cheaper way and it does work !!
ten dollar soldering station with jack held in extra "hand" This is the four dollar helping hand from Harbor freight - the five dollar soldering iron and the the dollar solder from the local discount store. I am not counting the workbench (scrap shelf board)
Another shot of my soldering rig - keep the tip wiped down with a damp sponge or damp paper towel - keep it tinned. I have never tore one up. Cheap but adequate for this kind of stuff. Probably wouldn't work on a LM386 project but thats a different story.