Recently I had cause to make a 555 circuit on a breadboard for something else I was working on. When I was done with that I still had the circuit on a breadboard and I got thinking what if I mixed two of these with an exclusive or gate? What is here is the result of that.

## Step 1: Schematic

When I was completely finished I drew out the entire schematic of the project. It is a bit involved but I will break it down in subsequent steps.

## Step 2: Schematic Blocked Out

The whole schematic is made up of small circuit blocks. This step illustrates those.

## Step 3: Power Supply

There is a 3 terminal voltage regulator on the breadboard that supplies all power to the circuit. That regulator is supplied with unregulated low voltage direct current which I will address in the next step.

## Step 4: Raw Power Supply

I have a metal box on my desk I keep a step down transformer in. I use that reduced alternating current when I need power for my projects. Someone could use a wall wart or something to get low voltage out of. The 7085 regulator needs a couple volts over its output voltage in order to function. So anything over about 7 volts or so should do the trick. 9, or 12 volts would be great. I'll include a wider angle of my project, and a schematic of the raw side of the power supply here.

In the wider shot you can see a tan metal box in the back with black wires coming out of it going to another board with some parts on it. That is the raw side of the power supply that feeds the voltage regulator on the breadboard.

## Step 5: Astable 555 Timer

The most popular circuit of all time. It turns itself on, and off. This version is adjustable too. The smaller value capacitor you use for C1 the faster the circuit runs. Adjusting the variable potentiometer resistors R1, and R2 has an effect on circuit duty cycle as well.

What I do is I build the circuit with a large C1, say about 2.2μF, then I connect an LED to the output, and see if it blinks. If the LED blinks then I know I built the circuit properly. If I don't get any blinking then I know something is wrong. I then try to fix whatever that is.

I am providing two schematics here. It is the same circuit, just drawn differently. This circuit will be built twice for the project though.

## Step 6: Mixer

This is what I really wanted to do. I wanted to run the outputs of both 555 timers into this logic gate IC. The outputs of both 555 timers go into the inputs of a gate on the chip. The output of that gate gets fed into a preamplifier. I will cover the preamplifier in the next step.

## Step 7: Audio Preamplifier

I wanted to hear what the signal sounded like but did not feel as if the logic IC could supply enough power so I built this preamplifier for the circuit. It turns out the preamplifier itself is weak too, but it does work. I adapted this circuit from another schematic I found on the Internet, but I used a TL072 op amp as opposed to whatever that circuit called for. I imagine any single supply operational amplifier IC would work here.

This part of the circuit probably isn't even needed, but I didn't know that myself when I was building the circuit. So this step could likely be skipped. I'm including it because I built it though.

## Step 8: LM386 Audio Amplifier

Initially operating the circuit I felt I could use some more volume so I added this. It is a 50 gain LM368 amplifier and it really does boost the sound level up considerably. Again I am offering the same schematic in two different formats. Only one of these needs to be built for the project though.

## Step 9: Conclusion

I know I was brief with this article but I never know what people need to know. So if anyone has any questions please leave them in the comments and I, or someone else will try to answer them.
<p>Just checked out some of your instructables after you posted a comment on my drawer tool chest one . Am doing something similar to this instructable with Schmidt gates. Think this is how they do waveform synthesis. BTW, you should check out my &quot;pimped-up&quot; breadboard instructable! </p>
<p>I have a few breadboards I use. They're just different sizes. Most of the time I can't even fit my big breadboard on my workbench. So I like using just the little pieces a lot. My last electronics project is kind of a breadboard peripheral. It is halfway done now, but stalled out. I'll get back to it someday. It is going to be a variable power supply, with a little built in audio amplifier, and speaker.</p>
<p>Hi i saw your instructible and was very interesting, i was wondering if you could help. I have just recently built a pwm synthesiser usingg lm358 dual opamps, i am also building a sequencer circuit built with 4017 and 555 for the clock, i am just unsure how to combine the two circuits together so i have sequencer synth... any tips would be great.</p>
<p>You can do a web search using select key words and see if that turns up some relevant schematics. This came up for me </p><p><a href="https://www.youtube.com/watch?v=oRvGqqgnMwI" rel="nofollow">https://www.youtube.com/watch?v=oRvGqqgnMwI</a></p><p>In the description there is a link to a schematic too. No op amps, but I am not sure what you are doing with them in your circuit. Anyways, browsing the net for circuit ideas is a popular method for me to use today. There are so many circuits out there that it is rare I cannot find something similar to what I want to make.</p><p>This article is mostly just little circuits that I found here, and there, and strung together.<br></p>
<p>Just a note to let you know I have added this ( a year ago ) to the instructable:</p><p> Comprehensive Guide to Electronic Breadboards: A Meta Instructable</p><p>&gt;&gt; <a href="https://www.instructables.com/id/Comprehensive-Guide-to-Electronic-Breadboards-A-Me/" rel="nofollow"> https://www.instructables.com/id/Comprehensive-Gui...</a></p><p>Take a look at a bunch of project involving breadboards.</p>
<p>Thanks. Breadboarding is an obsession of mine.</p>
Ok, you put the request out for questions :) I have to oblige ;) Firstly, please bear in mind that I'm very much a novice at electronics (despite fast approaching 51yrs of age). I've dabbled in the past (20 or so years ago) and even made an optical triggering fishing bite alarm that still works to this day. However, back then I was following instructions like putting a jigsaw together. Now, a bit older, I am trying to understand what each individual electronic component and collection of 'bits' actually does. The power supply I believe gives a nice steady well, supply of power :) A constant none wavering voltage and current. I hope I have that correct? The oscillator circuits (I built one of these for that bite alarm all those years ago) produce an audio tone? These are then combined in the mixer circuit. I'm not sure about the pre-amplifier and the power amplifier though. Just why do we need two amplifier circuits? What does the pre-amp give to the whole overall effect? I hope to attempt this collection of modular circuits in a few weeks (I'm awaiting delivery of a rather large collection of electronic components to kick start my learning process). To me the whole thing looks complex but I like the way you have broken it down, thank you :)
The supply here is voltage, not current regulated. The oscillators put out square waves that if you hooked them up to speakers would make sounds. The final sound of this circuit is just a combination of the two oscillators. I said in the text that 2 amplifiers are not needed but the first ampifier I built was not strong enough. The preamplifier could be omitted but being as I already built it it was easier for me to just leave it. <br> <br>Initially my concern was loading the logic gate output with the speaker. I'm not sure what would have happened then, possibly the gate would have burnt out. Likely whatever happened I would not have been too happy about it, so I never tried it. <br> <br>The point of my article was to show that a &quot;complicated&quot; circuit is just a collection of simple circuits. My motivation for building the circuit to begin with is somewhat complicated though. I had a bit of it on the breadboard for doing some signal injecting and I decided to do some fun breadboarding for nostalgia I suppose. <br> <br>A long time ago I used to breadboard for fun all of the time. Now not so much. <br> <br>If you build this you should build it one circuit block at a time, testing as you go. Either that or mistakes may be difficult to track down. <br> <br>Build the power supply first, and make sure it works, then one oscillator, make sure it works, then the other, test it, then the logic gate is pretty simple, the next stage will determine if it works, or not. You can skip the preamplifier I believe. It does a little, but not much. <br> <br>To go further with this project you could build another power supply that only powers the LM386 as that IC can handle a much higher input voltage than the logic gate can. Or maybe you could substitute that logic IC for another CMOS one that takes a higher input voltage. Then I imagine this noise maker might be quite loud. It might make a decent alarm or something.