555 timer IC idea

[oliphaunt]

Ok folks, the amount of electronics ignorance I am about to show is stunning, so if that scares or offends you hit "back" now! 

I recently picked up a 555CN timer IC and have been thinking about what could be done with it.  What I would like to make is a square wave tremolo, a simple on/off machine gun stuttering effect would be fine for now, it can get more sophisticated later.  I know the 555 can generate "pulses" and flash an LED (I've been doing a good bit of searching but don't have the information I am looking for yet). 

So, the basic question is: what comes out of the output the 555?  Is just variable voltage levels?  If so how much voltage?  I now that transistors are dependent on certain voltages on the various legs to work correctly, and I'm thinking that if the 555 sends raw voltage (like a battery) it could be used to short out and/or turn on a transistor, allowing signal to pass or not through the transistor creating my stuttering effect.

Surely this is a ridicuous idea, it can't be that simple.   I see projects where an LED and a photocoupler are used to create veriable resistance, but that other possibilities are there?  Thanks for any ideas.

[cpm]

not going into much details here, just take into account two things:
555 will switch close to rail levels, in a hard way that is prone to induce ticking noise in the audio path. you must design very carefully the layout for components and traces to avoid this.
you can use these high and low voltages applied to whatever audio switching circuit you want, may be as simple as a transistor, but a hard switching may also cause "pops" and noises in the audio.

[Meanderthal]

 Search " Hysterisis oscillator", it's been done and yes it really is that simple... Ticking and all...

[sean k]

If you look at the tremolo, or LFO, on Tim Escobedo's synth stick at Folk Urban he has a depth control of the LFO then a resistor to the base of a transistor with a 100uf cap to ground. I think this charging and discharging of the cap on the base helps to reduce the abruptness of the square wave from the LFO.

Also I have a 555 setup as they normally are and it doesn't do what I want it to do so I read up on the little buggers and though I haven't seen it yet, at least not what I wanted, I figured something out by doing the calculations with on and off times. I want to control  pulses to ringing oscillators and figured that I needed the same on times but off times decreasing with increasing rate and figured out a resistor to V+ and then to a pot with another resistor off the bottom to pin 6 and 2 and pin 7 going to the wiper allowed this to happen..., in theory. There was stuff about equalising on/off times, which may be what you want.
http://home.cogeco.ca/~rpaisley4/LM555.html

Another possible is to simple use the 555 to drive an LED off the collector of a transistor and use an LDR on your signal to somewhat smooth things out.

[Meanderthal]

 I was wrong- the hysterisis oscillator isn't using a tranny as a switch, it's directly switching the audio... your idea might go a long way towards fixing that! the led\ldr will get rid of the ticking alright as long as the layout keeps things apart, but wouldn't it be more of a fender tremolo and not very choppy at high speeds?

[sean k]

What about running pin3 on the 555 through a resistor and throwing that at a CA3080?

[darron]

don't assume an LED will fix the problem, because once you get that in there you start to draw a higher current. if you take the led path then consider experimenting with putting a small value cap less than 10uf on the led to give a very slight fade in / out.

also, use a 3pdt switch and have it turn the circuit led on, as well as the LFO on/off so there's no chance of bleedthrough in bypass mode.

isolate the lfo rail from every other signal rail with limiters.

[darron]

i know that you want to use your 555. but you could also use any low power dual opamp like in  the bottom half of this bitcrusher:
http://experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Analog%20Bit%20Crusher.gif

it does exactly what you want. minus the sample+hold on the top. i'd change c4 to about 2.2uf to make it more of a suitable range for what you need.

[Meanderthal]

 Yeah, I don't think anybody's really gotten a simple 555 tremolo to work tick-free yet... good point about the current thing, the tick problem only seems to get worse as ya add more components. Rumor has it cmos 555s are quieter... would be nice though if there were a simple solution using a 555

OTOH, if you just want a simple square wave tremolo and have transistors in mind, how bout the kay tremolo?

[darron]

then stick it in a wah shell so that when you pull the paddle back it goes faster!

[Meanderthal]

 Hmmm... separate batteries and circuit boards for the timer and gain stages? Maybe.... separate enclosure for the 555 with cv out...lol! so much for simple, but might be useful for syncing up multiple lfos? Just tryin to think of a practical musical way to use a 555 besides as an oscillator....

[darron]

you could make an atari punk console:

http://www.getlofi.com/?p=518

it uses a 556 (dual 555) but you could buy another 555 and make it with two.. hehe... but it would be easier to buy a 556.

hmm ):

[Meanderthal]

 +1 on the APC! That's the most fun I've had with 555s so far...

[oliphaunt]

Guys, thanks for the suggestions.  I will try the Hysteresis Oscillator and see what it is all about.  This is a case where I am not so much looking to build a specific effect.  I already have a nice Trem that does the stuttering thing, so I am not really interested in building another specific circuit such as the Kay to create the effect.  I just want to see if I can learn about the 555 and how I might be able to use it.  The stuttering thing was the first audio application that came to mind as I search for info and learn (very little) about what the 555 does and how I might use it.

Honestly I still can't say I know what the 555 does or exactly what comes out of the output...

[smallbearelec]

http://www.smallbearelec.com/Projects/TremBear/TremBear.html

[earthtonesaudio]

The CMOS 555 is much better in terms of ticking.  Really the only time the bipolar version is preferable is if you need lots of current from the output.

[dubiousss]

i got his on the breadboard right now, hysterisis with 500k pot, instead of .1cap make 10uf it makes it an on off trem

[brett]

The CMOS 555 is much better in terms of ticking.

+1 for that.  It has a completely different output configuration to the BJT 555.  The CMOS device is low ampage, low noise and IMO underused in stompboxes.  It is perfect for things like modulators and bitcrushers.  Stable, predictable switching speeds from a microsecond to seconds using just a few parts.  You gotta love that.  Perfect for driving the gate of discrete CMOS like the BS170 and 2N7000.  Or IRF and MTP for high-power switching.  Then there's all of the applications as delays.....

[earthtonesaudio]

The CMOS device ... is perfect for things like modulators and bitcrushers. ... Then there's all of the applications as delays.....

  Cool stuff.

The CMOS 555 goes faster too, typically something 2MHz vs. 500kHz for the bipolar, as I recall.

[oliphaunt]

The CMOS 555 is much better in terms of ticking.

The CMOS device is low ampage, low noise and IMO underused in stompboxes.  ...Perfect for driving the gate of discrete CMOS like the BS170 and 2N7000.  Or IRF and MTP for high-power switching.

That sounds like the type of application I am looking for.  Coud you share any specifics or partial circuits?