simple electronic music box circuit

so today I'm going to be tinkering with a circuit  that was uh something that somebody on Reddit was asking about a few weeks ago and when I took a  look at it it looked like an interesting circuit so I figured I'd give it a play and just see what  happens the circuit is called the simple music box circuit and the link that the guy on Reddit sent  goes to this page homemade circuit projects it uses a couple of 555 timers and the good old 4017  decade counter which is you know a combination that

we've seen time and again for instance this  is the classic uh 555 plus 4017 implementation is the chase 10 LEDs along the 555 is just busy  clocking along quietly here and each time it clocks it uh triggers this guy to go further along  its sequence when it gets to the end it pops back very very straightforward circuit and excellent  beginner circuit and the one that we're looking at today takes this basic circuit and takes it  one step further so here on the left side is essentially what I had

in the on the breadboard  there is a five by five pin three is the output pin 14 is the uh clock input of the 4017 and the  rest of it is just the power and stuff but then the difference happens on the output we have a  bunch of diodes this thing says you can use pretty much any diode I happen to be using shotkey diodes  because I've got a bunch of them lying around and then there's a bunch of resistors all  summed together on the output which goes over to the second 555 timer now then if you'r

e  familiar with using 555 timers in an a stable multivibrator AKA just a straight up oscillator  setup this is not exactly the standard version this is over here this is from the forest Mims  book which we've we've seen before and if you haven't I will put a link to it down below  because it is an awesome classic resource so the classic circuit here uses two resistors and  one capacitor these two resistors can be replaced with a potentiometer with the wiper coming in the  middle here on pin sev

en and the two resistors plus the capacitor are the timing elements there's  two times that happen here one is basically based on R2 plus the capacitor and one is based on R1  plus R2 and then the capacitor so as the capacitor charges and discharges like this the two internal  comparators that are on pins two and six uh compare it to the threshold voltages that are set  and Trigger the internal flip-flop to flip or flop and then pin seven is the discharge which pulls  this to this point here to

ground and discharges the capacitor through the resistor so that is  this and then once pins two and six hit the other threshold the lower threshold um it flips the  flip-flop again because that's what flip-flops do and it starts charging this time through R1 and  R2 but that's not how this little oscillator works we've still got pins two and six tied together  as usual but pin three the output is tied to a single resistor so as that goes high or  low it is controlling the charging and dischargi

ng of this capacitor through this  one resistor and then on the second one so this one over here is acting as a clock that  toggles the 4017 to just change outputs each time so it's running at a relatively low speed  this one is running at a fairly high speed an audio frequency speed what it looks like is  happening is as each of these outputs go high it puts the full VCC voltage through  this resistor and then through this one so this becomes the charge resistor and this one  becomes a discharg

e resistor theoretically anyway and then all these three are all these resistors  here are different values so that you get a different frequency out of your audio oscillator  and then this is just a straight up amplifier I will link to this page of course down below  here is the parts layout I want to go and demonstrate the two different oscillators just  for a moment and then we'll build this thing so here is the the two different 555  oscillator circuits I was talking about they are almost id

entical the only  difference is this one over here is the one for this music box circuit and it has one less  resistor in it I'm just using potentiometers from both of them so they get the speeds lined  up for the demonstration here but as you can see you can change the speed of them  just by adjusting the potentiometers so this oscillator over here the potentiometer  is acting essentially as two resistors one between VCC and pin seven  the discharge and the other one between uh VC or between th

e discharge VCC and  the pin 2pn6 and capacitor setup just like we saw in the forest Mims book this one on the other  hand just has it set up as a single resistor note the other way it's not going anywhere and that  is just between pin three the output and pin two and six the two threshold comparators so  that's a little bit different but I'm going to use actually both of these in the circuit that  I build just because just to show the general versatility of playing with 555s let me grab some  p

arts and put this together and I'll be right back Well that took a little while to put  together but I've got it together and I decided to put a variable resistor  in here it might look like I've got two resistors in here but they're both in series  with each other they are as it shows on the on the web page Just Between the output pin 3  and the threshold pin two and six just uh put them in series just to give me a little bit uh  lower speed going on anyway so that is the one that the circuit d

esigner wanted here is the 4017  with all the diodes coming out of the outputs and series resistors just like we had in the schematic  there are two of the 10 outputs that are not used because the guy that designed the circuit  wanted a couple of rests in his musical output just for artistic reasons which is cool  and of course the different values of resistors are going to give us a different frequency on  our audio oscillator which is this one over here now this one is set up more like the  cl

assic course MIM circuit it has the discharge resistor there and then the charge  resistor is essentially whichever one of these happens to be high at the moment so let me  plug in the speaker and assault your ears and we can of course speed it  up no we can't even slow it down see each note with each flash here it's kind of cool quiet you so you could you  know change those resistors make any notes you want right now there's only eight notes in  use out of the ten in the sequence so I guess he

wanted to go with just normal musical stuff  so that's two bars of quarter notes essentially yet another use for the 555.  this time with a couple of them I think you probably uh recognizing by now the  555 is one of my most favorite chips out there it's been around forever and it is just so damn  versatile there's so many things you can do with it and I've only scratched the surface in the  last few videos where I've been playing with it um if you want to see me explore it  further let me know

in the comments far too loud I didn't really need an amplifier but  the circuit called for one so I threw it in there um yeah so this was fun I do  like playing with these things and uh yeah I guess that's it for now  questions comments down below as usual and for those of you wondering what the beer this  is Red Alert Red Ale from Full geek Brew lab in Winnipeg they don't describe much about it other  than just smooth and malty Red Ale but there is a moderately humorous Star Trek inspired story

on  the back of the can so that that's fun too anyway um that's everything for now I'm  out of here talk to you later