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  #1  
Old 06-16-2009, 04:53 PM
Fenris Fenris is offline
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Default Cascade 4017 for 10 x 18 LED matrix

Hi all

As a young callow youth I remember, in one of the electronic mags, an LED based oscilloscope. I especially remember wanting to build one and the fact that the LED's were far to expensive at the time.

Well I stumbled across the circuit again recently and then many more variations on a theme. So the time has come to build one!! Firstly let me state this is a fun project just to keep me occupied and I am well aware of the limitations of using the end product as an oscilloscope.

Now the original has a 10 X 10 LED matrix as the display. An LM3914 x CD4017 are used to create the matrix. An LM555 IC acts as the clock. Now I fancy a 10 x 18 LED matrix so I need to cascade a pair of 4017's to do this. I am also using a 4011 IC as the clock and as an internal trigger. a second 4011 is to be used to 'join' the 4017's together so that they cycle from 1 to 18 repeatedly. I have drawn up 'my circuit' based on various schematics but just need an OK on the way I have setup the 4017's. Have I done it correctly?

I will also be using a 741 op amp circuit as an amplifier for the input to the 3914.

I attach the picture of the circuit.

regards

Fenris
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  #2  
Old 06-16-2009, 05:10 PM
Audioguru Audioguru is offline
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Each column of LEDs will be lighted for only 1/18th of the total time so they will look very dim. The max current from the 4017 is only about 22mA so each LED will look as dim as one with a continuous current of only 1.2mA.
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Old 06-16-2009, 05:20 PM
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SgtWookie SgtWookie is offline
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Nope, your cascading won't work with a single 4011, as those are NAND gates, not AND gates which is what is required. However, you could cascade a couple of NAND gates to emulate an AND gate:



Also, note that in your schematic, you have pins 11 and 12 wired together. They are both outputs; this is a "no-no". Pin 12 is not used in this application. Pin 13 is an input.

[eta]
Audioguru's correct; it'll be a pretty dimly-lit display. You should be able to see it in a dimly lit room, though.

My version was derived from this datasheet: http://www.synthdiy.com/files/2002/hef4017b.pdf
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Last edited by SgtWookie; 06-16-2009 at 05:28 PM.
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Old 06-16-2009, 06:58 PM
Fenris Fenris is offline
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Hi there

Thanks for the heads up guys. I am aware the LED's won't be particularly bright, a bit like me judging by my cock-up on the drawings . Any hoo here is the corrected version for your approval!

regards

Fenris
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  #5  
Old 06-16-2009, 11:12 PM
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SgtWookie SgtWookie is offline
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Fenris,
Your clock generator won't work as you have it drawn (lower left corner).
Instead of using 4011 NANDs for the clock and the 4017 cascade AND, use 4093 NANDs; they have Schmitt-trigger inputs.

Then move the cap from between the two NAND gates, connect one end to the input of the leftmost NAND gate and the other end to ground.
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Old 06-19-2009, 09:27 PM
Fenris Fenris is offline
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Hi Sgt

It's more a question of what I have to hand component wise at the moment. But heeding your warning about the 4011 I have made a 10 X 10 unit that uses 1 3914 and 1 4017. Also the clock os a faithful ol' 555.

The LED matrix is constructed from 2 squares of vero board. These have had alternate strips removed and are now face to face with the tracks at right angles to each other. Each LED is mounted with their legs in adjacent holes which puts them at 45 degrees.

I currently have, roughly, a 33hz sine wave displayed on the matrix. I am also using a 741 pre-amp to boost the signal. I have probed my voice mod with it to see the square wave made by the 555 chip . LED brightness isn't a major issue although it will need a shroud in daylight if the sin is directly on it.

I have found another 4017 cascade circuit by Bill Bowden which looks promising. I fancy getting some 5x7 LED display modules maybe 4 for a 140 LED display? it would be easier than making the matrix myself

Again this is just a bit of fun for me. But the one I have now can at least indicate the presence of a signal even if not of any measurable use. I attach Mr Bowdens cascade 4017 circuit.

regards

Fenris
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  #7  
Old 06-20-2009, 04:36 PM
Fenris Fenris is offline
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Hi there

Well I have found a circuit design that uses 3914, 4017 and 4049 chips. This is used to drive 9 LED matrix modules. Now the spec'd modules are LITE-ON LIP747 5 x 7 LED display modules. Now I am trying to find out what they are rated at, as rapid do not stock this specific make, so I can select a replacement from their stock. I believe I need column common cathode or row common anode depending on how each manufacturer references them (basically they are the same of course)

The Lite on site doesn't want to play ball with me at the moment so I am having trouble getting the spec's and google thinks I am after a boeing 747. Has any one got a recommendation as to what rapidonline stock item would be a suitable replacement. Green types also seems have less of a power requirement if that broadens the choice.

regards

Fenris
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Old 06-21-2009, 08:51 PM
Fenris Fenris is offline
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Default The schematic for a 141 LED solid state scope

Hi Guys.

Heres the circuit I am looking at building. I have corrected the LF353 pin out for power but I am wondering where the GND is for it as it is only showing the +ve and -ve rails.

Sgt's resistor is Sgt Wookie's addition from an earlier question about the 7555 clock.

The 4011 U5-A is for setting the trigger as internal or external but I don't quite get how it works as it looks to me like if pin 1 and pin 2 are both getting +12V then the reset on the 4017's is going to be firing permanently?

The VSS and VDD pins of the 4049's seem a bit odd. On the ones that drive the rows the VDD pin 8 goes to +12V and VSS to GND on the 4049's that drive the column's the VDD pin 8 goes to GND and VSS goes to +12V. Is this Correct?

I have tried e-mailing the guy who designed the circuit but his website hasn't been updated in quite some time. There are images of the built unit and screens showing various wave forms.

http://www.geocities.com/rlaude2000/ledscope.htm

regards

Fenris
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Old 06-21-2009, 09:57 PM
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Quote:
Originally Posted by Fenris View Post
I have corrected the LF353 pin out for power but I am wondering where the GND is for it as it is only showing the +ve and -ve rails.
The LF353 doesn't need a ground reference itself. It's a dual-supply op amp.

Quote:
The 4011 U5-A is for setting the trigger as internal or external but I don't quite get how it works as it looks to me like if pin 1 and pin 2 are both getting +12V then the reset on the 4017's is going to be firing permanently?
This schematic has a number of problems. I stumbled over it a few years ago. This is just one of them.

Quote:
The VSS and VDD pins of the 4049's seem a bit odd. On the ones that drive the rows the VDD pin 8 goes to +12V and VSS to GND on the 4049's that drive the column's the VDD pin 8 goes to GND and VSS goes to +12V. Is this Correct?
No. For the 4049, Vdd is always on pin 1, and Vss is always on pin 8.
Quote:

I have tried e-mailing the guy who designed the circuit but his website hasn't been updated in quite some time. There are images of the built unit and screens showing various wave forms.

http://www.geocities.com/rlaude2000/ledscope.htm
Hard to say if you'll ever get a reply. I imagine that the person has been inundated with E-mails over the years; they may have gone so far as to change E-mail addresses just to get away from all of it.
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  #10  
Old 06-21-2009, 11:00 PM
Fenris Fenris is offline
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Hi Sgt

OK then so the LF353 Is OK as is.

The trigger. Consider the Forrest Mimms version. Pin 1 of the 4011 to row 1 of the matrix, pin 2 of the 4011 to column 1 of the matrix that would make more sense I think.

The VSS VDD problem. Wire these correctly then as they should be. I have read a bit about the 4049 and think I understand. If a positive signal is sent in it comes out negative and vice versa?

Is this circuit salvageable? the 4049 is the chip you mentioned as a candidate to cascade 4017's. Is this part of the circuit correct?

I think the 4011 trigger can be sorted as per Mimms. Or left out.

If you consider it pointless due to inherent design problems where do I go from here? joining 3914's to expand a matrix display seems a hell of a lot easier than cascading 4017's. I would really like to pursue 'knocking up' a solid state oscilloscope. The one I have at the moment is bloody great

Having removed the 741 pre-amp circuit The wave forms presented on the 10 x 10 display are much better formed. Obviously the pre-amp I was using was dirtying the signals I was investigating. I have it strapped to my voice mod at the moment and am watching the changing square wave on the display of the 7555 chip that controls the modulation rate. For proof of presence of a signal for basic fault finding I think it could be very useful in this instance. I have also been changing the capacitor of the scopes timer chip to be able to view frequency's outside of the fixed range with great success. I hope I am learning something

Your guidance would be much appreciated.Heres a pic of it in action. The Flash killed the display a tad but you can just make out the illuminated leds top and bottom forming the squarewave.

regards

Fenris
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