Author |
Message |
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
|
Back to top
|
|
|
analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
|
Posted: Fri May 10, 2013 5:05 pm Post subject:
|
|
|
Hi.
I haven't really thought this through fully (so no schematic yet) but couldn't this be achieved by using an LM3914 bargraph chip in dot mode? If it can, it's quite likely that somebody already has done it, so a search for the LM3914 might turn up something. I'll give it some more thought...
Gary |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Fri May 10, 2013 5:08 pm Post subject:
|
|
|
LED bar graph DOT mode, haven't checked out yet, but this sounds like what I need. Thank you, I'll have a look |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Fri May 10, 2013 5:18 pm Post subject:
|
|
|
YEEEES! Exactly what I was looking for.
I didn'T look up for the bargraph thing, because I didn't know
about the DOT mode. And they are cascadable!
And the most important feature: the chip is not obsolete
Thank you very much!
Now I'm so happy, this forum is so fucking great!!!
greetings |
|
Back to top
|
|
|
analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
|
Posted: Sat May 11, 2013 3:03 am Post subject:
|
|
|
I might have just found a snag. If you look at this thread:
http://electro-music.com/forum/viewtopic.php?highlight=lm3914+sequencer&t=19084
frijitz and zipzap (briefly) mention trying to use the LM3914 in a sequencer and having problems with the some pulse overlap (by which I assume they mean that the next 'dot' switches on slightly before the previous one has completely switched off). I don't know how much overlap there is, because I've not used this chip for anything other than an LED voltmeter-type application.
If this is the case, it might be possible to introduce a small delay using an RC combination between the LM3914 dot switching on and the 'opening' of a bilateral switch of the 4016/4066. I'm just thinking out loud here - I might have to try it and see what happens...
Gary |
|
Back to top
|
|
|
Uncle Krunkus
Moderator
Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
Audio files: 52
G2 patch files: 1
|
Posted: Sat May 11, 2013 4:16 am Post subject:
|
|
|
Another option would be to go through an ADC (analogue to digital converter, like the ADC-0804) and then to a binary to decimal, 1 of 8 decoder. It would be more complex and expensive than a simple LM3914, but would eliminate the overlap problem,... I think. _________________ What makes a space ours, is what we put there, and what we do there. |
|
Back to top
|
|
|
elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
|
Posted: Sat May 11, 2013 6:25 am Post subject:
|
|
|
If you were interested in triggers rather than gates, as output, using a trigger conditioner on each output would prevent the overlap problem.
It's a Ken Stone circuit, but the reference I usually use is the one on Fonik's baby-10 sequencer schematic: http://modular.fonik.de/pdf/baby10.pdf upper right.... You can use a pot voltage divider on the voltage selection input (negative input of the op amp) and vary your pulse width too. I've generally used a trimpot, but a regular one (with appropriate resistors limiting each end of the range so you're not going full ground to Vcc) ought to work as well. |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Sat May 11, 2013 7:03 am Post subject:
|
|
|
I read the datasheet of the 3914 and it seems to be perfect for my purposes. Monday is Monday Then I'm gonna buy one or two
There's also this "this is not a waveshaper" thread, wich will be interesting too.
six chips could quantize a range of five octaves.
I'm glad that the 3914 is easy to operate, so I can build many modules
to make my planned "dilettantic built poor man's modular" compatible
to more professional control voltage standards until I got enough skills
to build more proper voltage control and stable circuits.
One day I will have a real analogue "emulation" of the Nord Modular G2
This new electronics hobby makes me feel like a ten year old boy in
a star trek universe |
|
Back to top
|
|
|
richardc64
Joined: Jun 01, 2006 Posts: 679 Location: NYC
Audio files: 26
|
Posted: Sun May 12, 2013 3:00 am Post subject:
|
|
|
You want a "digitizer" -- a flash ADC.
http://www.paia.com/ProdArticles/ek7.htm
The output bits would go to the Select pins of a decoder or mux.
The LM339 is the equivalent quad single-supply comparator. _________________ Revenge is a dish best served with a fork... to the eye |
|
Back to top
|
|
|
bunker
Joined: Mar 19, 2009 Posts: 58 Location: Manchester, UK
|
Posted: Sun May 12, 2013 3:32 am Post subject:
|
|
|
analog_backlash wrote: | I might have just found a snag. If you look at this thread:
http://electro-music.com/forum/viewtopic.php?highlight=lm3914+sequencer&t=19084
frijitz and zipzap (briefly) mention trying to use the LM3914 in a sequencer and having problems with the some pulse overlap (by which I assume they mean that the next 'dot' switches on slightly before the previous one has completely switched off). I don't know how much overlap there is, because I've not used this chip for anything other than an LED voltmeter-type application.
If this is the case, it might be possible to introduce a small delay using an RC combination between the LM3914 dot switching on and the 'opening' of a bilateral switch of the 4016/4066. I'm just thinking out loud here - I might have to try it and see what happens...
Gary |
+1. I thought about using this chip for sequencing too but I didn't get beyond the data sheet after reading the section relating to 'overlap'. I'm sure there will be a way around it as others have mentioned. If you do have a crack keep us informed! Oh and good luck!! |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Sun May 12, 2013 4:20 am Post subject:
|
|
|
I thought dot mode would only output at one pin without overlap ?? _________________ Is the future obsolete? |
|
Back to top
|
|
|
bunker
Joined: Mar 19, 2009 Posts: 58 Location: Manchester, UK
|
Posted: Sun May 12, 2013 4:58 am Post subject:
|
|
|
From the data sheet..
"When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is avoided. Various novel displays are possible."
"The display driver does not have built-in hysteresis so that the display does not jump instantly from one LED to the next. Under rapidly changing signal conditions, this cuts down high frequency noise and often an annoying flicker. An “overlap” is built in so that at no time between segments are all LEDs completely OFF in the dot mode. Generally 1 LED fades in while the other fades out over a mV or more of range (1). The change may be much more rapid between LED No. 10 of one device and LED No. 1 of a second device “chained” to the first."
This feature doesn't appear to be something that can be 'turned off' so to speak. The CGS method mentioned above looks like a good idea although from the description adjusting the ref voltage for the comparator will also stretch the pulse proportionally? I might be wrong tho |
|
Back to top
|
|
|
bunker
Joined: Mar 19, 2009 Posts: 58 Location: Manchester, UK
|
Posted: Sun May 12, 2013 5:06 am Post subject:
|
|
|
Is your ultimate aim to produce a quantized voltage from something cyclic such as an LFO or from a non cyclic source such as a keyboard? Do you need uniform length of the high and low times of the gate or trigger pulse or do you need control over them? Its got me thinking about different uses of the LM3914! |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Sun May 12, 2013 7:29 am Post subject:
|
|
|
it is supposed to be driven by all kinds of cv sources. keyboards, lfos, sample/hold.
If there is a small millivolt output on some of the inactive output pins, couldn't
this be avoided by the use of diodes? I think, I'd have to use diodes
anyway like on the 4017 baby sequencer. So if the pin outputs 100mV, but
the forward voltage of the diode is ~ 500mV, it would be mutet, or??? _________________ Is the future obsolete? |
|
Back to top
|
|
|
bunker
Joined: Mar 19, 2009 Posts: 58 Location: Manchester, UK
|
Posted: Sun May 12, 2013 7:54 am Post subject:
|
|
|
I know what you mean. It depends on whether the voltage on the pin is held high AFTER the next pin is selected which I assume it must do? If so the diode will still be conducting after the next pin has been selected which defeats the object. A better method might be to generate a trigger pulse from the voltage on each pin. The pulse length can be set independently of the high period of the 3914 pin. It would involve a circuit for each pin and up the parts count. I can't think of any other way of shortening the high period of the 3914 pin output (which is what were talking about) |
|
Back to top
|
|
|
elektrouwe
Joined: May 27, 2012 Posts: 143 Location: Germany
|
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Sun May 12, 2013 11:35 am Post subject:
|
|
|
my intention was a voltage quantizer, for sequencer I'm happy with 4017.
If other pins output a voltage while inactive, I could live with it, if the voltage, which is unintentionally added, would be constant all the time.
would be the same like a small DC offset. _________________ Is the future obsolete? |
|
Back to top
|
|
|
richardc64
Joined: Jun 01, 2006 Posts: 679 Location: NYC
Audio files: 26
|
Posted: Mon May 13, 2013 3:44 am Post subject:
|
|
|
The pAia circuit I posted outputs 4 bits = 16 steps. ONE chip & a bunch of resistors. Add a decoder or mux. _________________ Revenge is a dish best served with a fork... to the eye |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Mon May 13, 2013 4:26 am Post subject:
|
|
|
Sixteen different states, okay. but they will be outputted as a number
of some complex 4-bit-patterns.
I'm still at the very beginning of learning about electonics,
but I'll try both designs.
must solder a new 386 amp and vco first...
I always give the stuff away, that's why my
synth never gets finished LOL
can I use any opamp for the digitizer? got a few LM324 and TL074.
And I have to find out, what a decoder/mux is.
I'm expecting some device, which takes the 4-pins-patterns
from the op amp digitizer and has 16 output pins?
greetings _________________ Is the future obsolete? |
|
Back to top
|
|
|
richardc64
Joined: Jun 01, 2006 Posts: 679 Location: NYC
Audio files: 26
|
Posted: Mon May 13, 2013 4:43 am Post subject:
|
|
|
cablebob wrote: | Sixteen different states, okay. but they will be outputted as a number
of some complex 4-bit-patterns. |
Right. A decoder/mux would have one active output depending on the 4-bit code.
Quote: | can I use any opamp for the digitizer? got a few LM324 and TL074. |
The 324 makes a poor comparator, which is what the op amps in digitizers are doing. I'm pretty sure the TL0xx, when used as a comparator, would have to be dual-supply powered. I could be wrong, though. _________________ Revenge is a dish best served with a fork... to the eye |
|
Back to top
|
|
|
analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
|
Posted: Tue May 14, 2013 6:46 am Post subject:
|
|
|
Just to confirm what others have already said, after experimenting with the LM3914, I don't think that it's a good choice for a sequencer . I think that (theoretically) you could get it to work, but you'd have to add so much extra circuitry to it, that you might as well use the discrete comparators (unless there is someone out there who can prove me wrong - there usually is ).
Gary |
|
Back to top
|
|
|
beep
Joined: May 05, 2013 Posts: 105 Location: Germany
|
Posted: Wed May 15, 2013 12:48 am Post subject:
|
|
|
If you want a sequencer and miss the 4017's ability to play backwards, isn't there any chip, which does the same, but bidirectional?? _________________ Is the future obsolete? |
|
Back to top
|
|
|
analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
|
Posted: Wed May 15, 2013 7:58 am Post subject:
|
|
|
Hi cablebob.
There are several CMOS up/down binary counters available (e.g. 4029, 4510 & 4516). I used the 4029 in the sequencer for my "Super Stylophone" project:
http://electro-music.com/forum/topic-54950.html&postorder=asc
It's about half way down the first page (hand-drawn). These give binary outputs (unlike the 10 separate outputs of the 4017). I used just 3 of the outputs for an 8-step sequencer. To convert the binary output to 8 separate outputs, I used the 4051 single 8-channel multiplexer and then used the outputs of this to open the 4066 switches used in the CV circuits. I also added a D-type flip-flop (4013) circuit which made the sequence run alternately forwards then backwards (I called it ping-pong).
Now, I know your next question will be about cascading for (say) a 16-step sequencer. I haven't tried this. The 4029 is a 4-bit binary counter, so it does give a 0-15 count. What I haven't yet worked out, is how to combine that with 2 4051s to give 16 separate outputs. I'll have a think about that...
Gary |
|
Back to top
|
|
|
elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
|
Posted: Wed May 15, 2013 8:43 am Post subject:
|
|
|
The 4051 has an inhibit, and you could use the high-order bit and an inverter to alternately inhibit each 4051, or you could use the high-order bit, a single inverter, and an AND gate on each of the outputs. The latter is pretty expensive in terms of chip real estate, but may be simpler to understand.
I didn't re-read the datasheet in detail, if the inhibit puts the 4051 outputs into high impedance mode you'll want pull down resistors on the outputs to use the inhibit. |
|
Back to top
|
|
|
Cynosure
Site Admin
Joined: Dec 11, 2010 Posts: 966 Location: Toronto, Ontario - Canada
Audio files: 82
|
Posted: Wed May 15, 2013 1:30 pm Post subject:
|
|
|
Or use a 4514 to demux instead. I did that with a 4029 and it works nicely. _________________ JacobWatters.com |
|
Back to top
|
|
|
|