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555 timer circuit
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MusicMan11712



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PostPosted: Sat Nov 06, 2010 6:23 pm    Post subject: 555 timer circuit Reply with quote  Mark this post and the followings unread

While looking through a box of old files on music, I found my 555 timer circuit from a few decades ago. The actual object can be seen here (well, most of it): http://electro-music.com/forum/post-278450.html&highlight=#278450

So, here's the diagram. I may try to rebuild it to see if it still works as I know some of the wires fell off over the years.


555 circuit 002.jpg
 Description:
Steve's Ancient 555 Timer Circuit (probably from the mid to late 1970s).
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555 circuit 002.jpg


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PostPosted: Fri Jan 07, 2011 5:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just found another sketch of my ancient 555 timer sound device showing ideas I had for modifying it.


555 Circuit - sketch for redesign.jpg
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Second drawing of my ancient 555 timer circuit with ideas for revising it.
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JovianPyx



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PostPosted: Sun Jan 09, 2011 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

When do we get to hear what it does? Smile
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PostPosted: Sun Jan 09, 2011 12:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
When do we get to hear what it does? Smile


Seems to be on *now* on PHOBoS' port Wink

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JovianPyx



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PostPosted: Sun Jan 09, 2011 1:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmm. I was a tad late... He's offline...
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PostPosted: Sun Jan 09, 2011 1:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

It'll come back I guess
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PostPosted: Mon Jan 10, 2011 7:23 am    Post subject: Testing Dr. Steve's 555 Circuit Reply with quote  Mark this post and the followings unread

Thanks Dr. Steve for posting these schematics Wink

I've been experimenting with this circuit and will post my
findings and progressions in the next couple of posts:

The first thing I did was redraw the schematic so I could
understand a bit better what's actually going on.


DrSteve555 - Org .gif
 Description:
Original 555 circuit by Dr. Steve, redrawn by PHOBoS
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DrSteve555 - Org .gif



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PHOBoS



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PostPosted: Mon Jan 10, 2011 7:34 am    Post subject: Testing Dr. Steve's 555 Circuit Reply with quote  Mark this post and the followings unread

I noticed a couple of things from the original schematic:
pin 8 of the second 555 timer wasn't connected to V+
(I assumed this was just an error in the schematic)

Pin 3 of the first 555 timer goes to pin 5 of the second timer,
which makes sense, but it's also connected to pin 3
of the second 555 timer. Since the outputs of the 555 both
oscillate between V+ and V-, this would short the powerlines.

I know Dr. Steve made this circuit by experimenting, so I decided
to just give it a try anyway. It did do something but the second
555 got very hot. So I decided to change this part in the schematic
to something that seems to make a bit more sense.

I also looked up the 142n9 transistors, and found out they are NPN
instead of PNP so I redraw those aswell.

this resulted in the following schematic:


DrSteve555 - Rev1 .gif
 Description:
Dr. Steve's 555 Circuit modified by PHOBoS
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DrSteve555 - Rev1 .gif



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Last edited by PHOBoS on Mon Jan 10, 2011 8:31 am; edited 1 time in total
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JovianPyx



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PostPosted: Mon Jan 10, 2011 7:47 am    Post subject: Reply with quote  Mark this post and the followings unread

I noticed that too - about the pin 3 to pin 3 connection... Also, it's not clear to me where power + is connected. Is it on the upper "bus" that connects the pins 8?

I've seen circuits like this before, where outputs are connected together to get a kind of ring modulator sound. But as you point out, with pin 3 of one connected to pin 3 of the other, it's possible for + to connect to - through the output transistors. Some circuits like this have recommendations to use batteries that are partially drained so as not to provide enough current to allow damage to the ICs. A dubious recommendation at best I think. Low voltage can help too. Or one could simply put a resistor between the + rail and pin 8 of each chip to force limiting the current to some acceptable level. This would prevent chip self destruct and/or overheating.

I see that in your second schmatic (PHOBoS) you have eliminated the right 555 pin 3 connection to the other pin 3 - yet in both of Steve's drawings, they are connected together or can be through the switches. This connection would also appear to provide self modulation of the right 555 timer.

It might be interesting to use a high input impedance opamp to get a signal from the timing capacitor(s).

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Last edited by JovianPyx on Mon Jan 10, 2011 8:28 am; edited 1 time in total
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PHOBoS



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PostPosted: Mon Jan 10, 2011 8:27 am    Post subject: Testing Dr. Steve's 555 Circuit Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
I noticed that too - about the pin 3 to pin 3 connection... Also, it's not clear to me where power + is connected. Is it on the upper "bus" that connects the pins 8?

yes, power + is connected to the topline in the schematic (which is connected to pin 8 )

Quote:
I see that in your second schmatic (PHOBoS) you have eliminated the right 555 pin 3 connection to the other pin 3 - yet in both of Steve's drawings, they are connected together. This connection would also appear to provide self mutilation of the right 555 timer.

Since the second 555 got hot and it just doesn't make sense to me, I
removed that connection, It didn't really produce any usefull noise in this
configuration .

Quote:
It might be interesting to use a high input impedance opamp to get a signal from the timing capacitor(s).

yes, that will give a nice sawtooth/triangle Smile, I've actually used that with
transistors instead of opamps for fading LED's and producing sounds.

--------------------------------------------------------------------------------------
continuing from my previous post

I got some sound of it but only after removing the 220uF Cap,. (maybe
this is because I use BC547 of transistors)

So with the same components I came up with something that does
what I think the original circuit is intended to do. When the switch is closed
the 220uF cap is quickly charged which then (through the transitors) turns
the sound on. when the switch is opened the cap slowly discharges and
the sound slowly fades out again.

I changed the 4.7uF cap to 1uF since I like the sounds it produces at
higher LFO frequencies. I reduced the 220uF cap to 22uf for shorter
decays and I also made a slight change to get a line signal so I can
connect it to an amp.

posted below is the schematic and some sound samples.

(I'm currently using LDR's in series with the frequency pots and let the
setting sun control it. Excerpts will probably be uploaded later)


DrSteve555 - Rev2.gif
 Description:
Dr. Steve's 555 Ciruit Heavily modified by PHOBoS
 Filesize:  10.83 KB
 Viewed:  157 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

DrSteve555 - Rev2.gif



Dr Steve's 555 Circuit - Demo 1 (Jan 10, 2011).mp3
 Description:
With the switch closed and starting with all pots turned down,
then while sweeping the frequency pot of the second 555 timer:
- increasing the Pulse Width pot in steps
- increasing the Frequency pot of the first timer in steps
- increasing both pots (fun)

Download
 Filename:  Dr Steve's 555 Circuit - Demo 1 (Jan 10, 2011).mp3
 Filesize:  4.97 MB
 Downloaded:  305 Time(s)


Dr Steve's 555 Circuit - Demo 2 (Jan 10, 2011).mp3
 Description:
Triggered by my Treequencer and with a small (110ms) delay
turning all pots.

Download
 Filename:  Dr Steve's 555 Circuit - Demo 2 (Jan 10, 2011).mp3
 Filesize:  5.37 MB
 Downloaded:  258 Time(s)


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Last edited by PHOBoS on Sat Jan 15, 2011 9:21 am; edited 1 time in total
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PHOBoS



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PostPosted: Sat Jan 15, 2011 8:49 am    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: retracing the circuit from breadboard
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Last week Dr Steve was kind enough to turn on his webcam to retrace
the connections on his breadboard. unfortunately a lot of the componenta
are missing but we did manage to retrace some connections of the transistors.
There were a lot of unconnected wires and some had probably been connected
to Steve's potbox.

Posted below is the schematic that I got from that:
As you can see this also solves the question about the 2 555 outputs being
connected together. I might recreate something using this as a starting point
but for now I'll continue with my last schematic.


DrSteve555 - Bread.gif
 Description:
Dr. Steve's 555 Circuit, retraced form breadboard.
 Filesize:  9.29 KB
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DrSteve555 - Bread.gif



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PHOBoS



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PostPosted: Sat Jan 15, 2011 9:16 am    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: Solar Control test
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Here's a ±10 minute excerpt from my Solar Control Test with the circuit
triggered by my Treequencer. I placed 2 LDRs in series with the frequency
pots so that the frequencies changed over time while the sun was slowly
disappearing behind a building. sunny
And the added delay creates a nice phasing effect.


(Thanks to tjookum for the tip of using heat shrink tubing on the LDRs !)


Dr Steve's 555 Circuit - Solar Control Test (Jan 10, 2011).mp3
 Description:
Testing Dr. Steve's 555 Circuit with 2 LDRs changing the frequencies
controlled by the sun slowly disappearing behind a building.

Download
 Filename:  Dr Steve's 555 Circuit - Solar Control Test (Jan 10, 2011).mp3
 Filesize:  9.32 MB
 Downloaded:  293 Time(s)


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PHOBoS



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PostPosted: Sat Jan 15, 2011 9:54 am    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: CV control
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Next test: CV control.
Using a vactrol (LDR-LED combo) in series with the second 555 frequency
pot I was able to use a sequencer to change the frequencies.

I also made some further adjustments to the circuit.
- A couple of different caps to choose a different decay time.
(this was also suggested in Dr. Steve's second schematic).
- An extra cap to choose a higher frequency for the first 555.
- Resistors in series with the frequency pots so I can use the full range.
- A LED and an extra resistor to get rid of the soft noise when the circuit is
not being triggered. (This LED also functions as a very nice indicator)
- A simple trigger circuit connected parallel to the Trigger switch.
(before I just hooked up the Treequencer instead of the switch)

Posted below is the schematic and a recording done by using a sequencer
for both CV control and triggering the circuit. (and delay for the nice phasing)
If you listen closely you might notice that the circuit produces some weird
background noises too.


DrSteve555 - Rev3.gif
 Description:
Dr. Steve's 555 Ciruit Heavily modified by PHOBoS (rev3)
 Filesize:  17.89 KB
 Viewed:  150 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

DrSteve555 - Rev3.gif



Dr Steve's 555 Circuit - Pulsing Vactrol Drone (Jan 13, 2011).mp3
 Description:
Using a sequencer controlled Vactrol to change the frequency of the second 555.
Circuit is triggered by the CLK of the sequencer

Download
 Filename:  Dr Steve's 555 Circuit - Pulsing Vactrol Drone (Jan 13, 2011).mp3
 Filesize:  5.94 MB
 Downloaded:  271 Time(s)


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JovianPyx



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PostPosted: Sat Jan 15, 2011 10:00 am    Post subject: Reply with quote  Mark this post and the followings unread

The LED looks like it's drawn backwards...
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PHOBoS



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PostPosted: Sat Jan 15, 2011 10:18 am    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: LED
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JovianPyx wrote:
The LED looks like it's drawn backwards...

yes it looks like it. But that's the way it will function. geek
(was actually surprised by that so tried a different LED to make sure)

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PostPosted: Sat Jan 15, 2011 10:31 am    Post subject: Reply with quote  Mark this post and the followings unread

I figgered that would be the answer, but I had to make sure... very odd... That means the LED conducts only when pin 3 of the right 555 is at ground potential, so the + end of the circuit is somewhere else. I see two candidates, the trigger switch through the 2.2k through the base-collector diode (which might not be a good thing for the transisitor)

OR

possibly from + to the collector of left transistor through it's collector-base diode and then avalanching the emitter base junction of the right transistor (????)... Very odd indeed.

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PostPosted: Sat Jan 15, 2011 11:41 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
..,the trigger switch through the 2.2k through the base-collector diode (which might not be a good thing for the transisitor

I think this could be the right answer. I just took out the left transistor and
100K resistor (so the Emitter of the first transistor is floating) and the LED
responds the same. Don't know if the transistor likes it,. but it works (for now Wink)

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PostPosted: Sat Jan 15, 2011 11:50 am    Post subject: Reply with quote  Mark this post and the followings unread

The caps on the multi-switch might also be able to supply the + side of the circuit while they are charged. I'd bet the LED might change brightness when the cap value is changed.

Wonderful mental gymnastics, eh? Smile

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PostPosted: Sat Jan 15, 2011 1:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
The caps on the multi-switch might also be able to supply the + side of the circuit while they are charged. I'd bet the LED might change brightness when the cap value is changed.

well the LED reacts as follows: it flashes with the frequency of the first 555
between bright and dim and fades as the cap discharges (and the sound dies
out). Funny thing if I short the LED the sound barely changes (just doesn't die
out completely) Laughing

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PostPosted: Sat Jan 15, 2011 8:35 pm    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: CV control
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More CV controlled sounds.

Later that evening Tjookum joined me, excerpts from that jam session can
be found here. Basketball


Dr Steve's 555 Circuit - Hypnotropia (Jan 13, 2011).mp3
 Description:
Using a sequencer controlled Vactrol to change the frequency of the second 555.
Circuit is triggered by the CLK of the sequencer

Download
 Filename:  Dr Steve's 555 Circuit - Hypnotropia (Jan 13, 2011).mp3
 Filesize:  14.68 MB
 Downloaded:  265 Time(s)


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PostPosted: Mon Jan 17, 2011 7:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you so much for breathing new life into my ancient experimental 555 circuit, PHOBos. Thanks also to JovianPyx for adding to the discussion of the design and redesign, and to TJookum for participating in the demos.

Now that I found four more of my ancient 555s and a whole bunch of other parts (including the transistors taken from an old Magnavox Odyssey*), perhaps I can build your version--or something close to it--without taking my museum piece apart!

Steve

*http://www.magnavox-odyssey.com/Manuals.htm has a couple of versions of the service manual as well as operating manuals.

Footnote:
I used a 9 volt battery which was probably not operating at full capacity most of the time.
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PostPosted: Tue Jan 18, 2011 2:23 pm    Post subject: Testing Dr. Steve's 555 Circuit
Subject description: Rev 4
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MusicMan11712 wrote:
Now that I found four more of my ancient 555s and a whole bunch of other parts (including the transistors taken from an old Magnavox Odyssey*), perhaps I can build your version--or something close to it--without taking my museum piece apart!

I'd love to see what you come up with Smile

here are some more small modifications,.
two extra resistors for a better range, an extra cap and pot on the second
555 and the VACTROL inputs. For this I made a Vactroller which converts a
voltage from 0..10V to a resistance from 10K to 500K (I can actually set the
max from roughly 200K to 1M).

I don't know if I'll add more things, though the CV input of the first 555
looks very tempting (I already tried it with a sinewave Cool)


DrSteve555 - Rev4.gif
 Description:
Dr. Steve's 555 Ciruit Heavily modified by PHOBoS (rev4)
 Filesize:  20.95 KB
 Viewed:  172 Time(s)
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DrSteve555 - Rev4.gif



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PostPosted: Tue Jan 18, 2011 2:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

MusicMan11712 wrote:

Now that I found four more of my ancient 555s and a whole bunch of other parts (including the transistors taken from an old Magnavox Odyssey*),


Shocked Shocked Shocked

DR STEVE!! WHAT WERE YOU THINKING?? HOLY SHIT! Laughing

You did what? Why on earth would you pull out transistors from an Odyssey? Those machines are worth at least $500 up to several thousand! Shocked Sorry, but I am shocked!!! Shocked NNNNNOOOOOOooooooooo...... Those circuit boards are STUNNING!!! Shame on you Dr Steve! It's going to take me a long time to get over this one.... PUT THEM BACK! Crying or Very sad


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PostPosted: Tue Jan 18, 2011 6:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

LOL!!!!!!

I remember those little boards. They were fun to desolder!!!!

Either I found it in the trash or someone gave it to me as a non-working unit. I am guessing this was about 30 years ago or so. Back then, it was worthless.

Lemme see what other trash--errrr, I mean collector's items I have around here. I wonder what they are worth. Hmmmmmm. A Roland MT-32? A Casio CZ-3000? A Commodore 64? About 20 or so SCSI Cables?

Steve
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PostPosted: Wed Jan 19, 2011 11:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Laughing

I was going to comment but it turned into a rant and I hit the delete button! Laughing Anyway, I'll forgive you for your transistor barbarianism. You were not to know... Besides, I sent a Jupiter 4 to the garbage dump in 1992 because the on/off button was broken Shocked Laughing
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