Square Wave Generator (For Resonant Air-Gap Transformer)

I've decided on a project for the new year that is ~~less likely to lead to sterilization~~ better than my old project (which was a homebrew x-ray machine). My new project is something to wirelessly power some LEDs. I've done some research (read as, YES NACHO, I ALREADY GOOGLED IT!) and looked at puffin's unfinished instructable on IPT (it helped a lot). What I've found out is that to start, I will need something to generate a square wave AC signal. The circuit I decided on is a 555 multivibrator. One of my friends let me copy the schematic from his notebook. I've got a couple of questions still (and I hoped you guys could help). 1st. (Dumb Question) That symbol in the second picture is ground, right? 2nd. Once I build the multivibrator, how would I hook it up with the rest of the circuitry for my air gap transformer? (ie. where would the outputs on the circuit be?) 3rd. What does that symbol (it looks like it should just be a resistor symbol), next to the words speaker or other circuit mean? Is it just a resistor or is it actually the outputs I've been looking for? 4th. Is there anyone who has successfully done a project like this before (recently)? Thanks in advance for any help.

Picture of Square Wave Generator (For  Resonant Air-Gap Transformer)
DSC05434.JPG
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NachoMahma8 years ago
1) Yes
2) Pins 3 and 1. See BinaryBoy's comment.
3) It is a resistor. It represents the resistance of whatever load you use. If you can identify the load, that will point you to the output. In this case, the load is connected to 3 & 1.
4) Way too long ago for me to be a whole lot of help.
.
. The nature of your questions indicate to me that you've already done your homework - no need for one of my tirades. ;)
. Having to ask #1 doesn't mean you're dumb, merely ignorant. Ignorance you can fix (ask questions); can't do much with dumb. "The only dumb question is one you don't ask." "We all start out knowing nothing." &c.
 Hey, reading the last statement in your answer inspired me to ask you this, as I would feel stupid if I asked most other people (most other people don't have the same respect for other's ignorance as you) that being said:
Is the ground for the negative side say, a 9 volt battery, so obviously DC volts, or is this supposed to use 9 volts AC and the ground is just a ground? 
-Thanks
.  In the case of the schematic above, ground is 9V less than +VCC, but does not have to be at Earth potential. In theory, +VCC could be 109V and "ground" at 100V, but this could make interfacing with other devices difficult. Using an Earth(ed) ground means we all have a common point of reference.
.  +VCC is DC. You get pulsed DC between pins 3 and ground (pin 1).
 Sweet, thanks for the help, just another question, if I were to build this circuit and use a 9 volt battery then where would I put the negative lead from the batter socket, (would it go to the ground)? 
-Thanks again!
.  Yes, pin 1 = negative terminal of the 9V battery.
 Ok, thanks again for the help, their kind of primary things, but I need to understand it nonetheless. 
Gjdj3 (author)  NachoMahma8 years ago
Oh, and do you mind if I ask one more question? Is there any good way to test to see if it's working? (Can I just hook up an LED?)
Goodhart Gjdj38 years ago
Yes there are ways to test if it is outputing... and one way is to hook the Load to an 8 ohm speaker. Do you know the frequency of the square wave this circuit will generate? Do you know what you desire as a frequency?

This will determine what values to use for RA and RB
Gjdj3 (author)  Goodhart8 years ago
Okay, cool. Thanks! I'll go calculate the numbers to see what value of resistor will give me around 250 kHz.
. If you're using an LED for testing, don't forget the current-limiting resistor. . If you're going to use a speaker for testing, aim for 5-10kHz. You can't hear (and the speaker probably won't reproduce) 250kHz. That will tell you if the basic circuit works and then you can change components to get the desired freq.
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