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555 Timer & 4017 LED Circuit

Stuart

Jan 24, 2013
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I'm having problems with my circuit that I've designed and I feel as if I'm just a few meters from the finishing line here.

I have been trying to design an Electronic Roulette Wheel with the use of 555 timers, 4017 Decade Counters and LED's. Pretty straight forward right? The LED's will light up in a chaser fashion and randomly stop at an LED thus choosing an LED at random which will correspond to a number between 0 and 36 (37 LED's).

http://tinypic.com/r/wjudli/5
wjudli.jpg


Zoomed in view of 555 timer and connections.
http://tinypic.com/r/wjudli/5
2nkbic.png


My problem is that when I simulate it nothing happens, I'm at my wits end here so I'm hoping there is an Electronics wizard that can help me. I'm hoping that you can notice something rather obvious that I've missed, maybe a silly connection somewhere?

I know it's rather difficult to just look at a schematic and find out whats wrong with it and it's a lot to as but I'm really stuck and I feel so close to finishing my project.

Thanks,

Stu
 
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BobK

Jan 5, 2010
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Yes, you are missing something. The threshold and trigger pins of the 555 must be connected to the top of C3.

Bob
 

Stuart

Jan 24, 2013
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I'm assuming you mean like this?...

2zdxd13.png


It's still not working, back to the old drawing board for me :(
 

BobK

Jan 5, 2010
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Yes, like that.

Define not working. Are you getting pulses out of the 555?

Also, you have a switch for the power to the 555. When simulating is that switch on?

bob
 

Stuart

Jan 24, 2013
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I believe so yes, I just connected two LED's in series to the 555's Output pin and they are flashing so I'm assuming that's me getting pulses from the 555? and yes the switch is on when I simulate it.

What I mean by not working is that I expect all of my LED's to light up in a chaser fashion and randomly stop at one LED and keep it lit, but unfortunately when I simulate it the LED's do not light up.

The LED's connected to the AND Gates, however, all flash only once simultaneously as soon as S1 is pressed and nothing happens after that.

Stu
 

BobK

Jan 5, 2010
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I can't read the schematic well enough to determine if the 4017 part is working.

Bob
 

Stuart

Jan 24, 2013
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This is how I've cascaded my 4017's and how I've connected the LED's

3tvo3.jpg


Stu
 

Rleo6965

Jan 22, 2012
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I'm not good interpreting datasheet. Are you sure that 4017BD output pin can directly drive LED to lit?

What the part number of your and gate? It seems its output capable of driving LED to lit.

Maybe if you increase VCC supply into 12V will help to lit your LED and remove the current limit resistor.
 
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Stuart

Jan 24, 2013
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I'm fairly sure it can but I'm starting to doubt myself.

As for my AND gate I do not know the part number as my electronic workbench does not state what it is. All it says is "Value: AND2, Manufacturer:Generic, and Function:2 input AND."

I've tried increasing the VCC supply to 12 and nothing happened although I did not change my 4017's from 5V's to maybe 15V chips so I'll maybe try that. Unfortunately I'll need to do that later on today because I'm currently away from home :(

Stu.
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Yeah, the 4017 can drive a LED, but don't expect it to also be able to maintain a valid logic level if you're passing more than a couple of mA to the LED (see the specs for more details).
 

Rleo6965

Jan 22, 2012
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I'm fairly sure it can but I'm starting to doubt myself.

As for my AND gate I do not know the part number as my electronic workbench does not state what it is. All it says is "Value: AND2, Manufacturer:Generic, and Function:2 input AND."

I've tried increasing the VCC supply to 12 and nothing happened although I did not change my 4017's from 5V's to maybe 15V chips so I'll maybe try that. Unfortunately I'll need to do that later on today because I'm currently away from home :(

Stu.

DC supply NE555 and cmos ic 4017 , AND gate ic must be same to avoid interface signal threshold problem.
 

Stuart

Jan 24, 2013
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DC supply NE555 and cmos ic 4017 , AND gate ic must be same to avoid interface signal threshold problem.

I'm not sure I completely understand you here what must the AND Gate IC be the same as?

Here's me thinking I was close to getting my design simulating correctly :(

Man is this good fun but boy is it hard work haha :D

Stu
 

Stuart

Jan 24, 2013
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Yeah, the 4017 can drive a LED, but don't expect it to also be able to maintain a valid logic level if you're passing more than a couple of mA to the LED (see the specs for more details).

Do you (or anyone else) know how to overcome this problem?

I thought I was so close to getting this to work as well :(

Stu.
 

(*steve*)

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As long at the outputs you use to drive LEDs are not also used as inputs to other logic, you'll be fine.

I can't see that you've done this, but you'll know for sure.

If you have done this, you have a couple of options:

1) use a transistor to buffer the logic output
2) use a spare gate to buffer the output
3) lower the LED current to the maximum sink/source current specified in the datasheet that will still allow the logic levels to be preserved
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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I'm not sure I completely understand you here what must the AND Gate IC be the same as?

I think the suggestion is that you need to use the same logic family.

So stick to all the same type of CMOS. It's OK to combine 4000 series and 74C/74HC, but you can get into a little (or a lot of) trouble if you include other families in the mix. Any of the CMOS families with a T in their name (74ACT, for example) have distinctly different logic levels.

Wikipedia does a good job of listing the different families. Make your life simple and stick to a single family.
 

Rleo6965

Jan 22, 2012
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Here's sample of circuit how to connect all supply of your ic to +15V.

Also included hex buffer LED driver for brighter LED. You need 6pcs of CD4069 for 36 LED. You use 1 pc npn transistor to drive the remaining 1 pc LED. You can change value of current limit resistor for LED to adjust brightness of LED.

I can't draw the whole circuit. I'm busy right now with other projects.:D

You can also tie the supply of cmos AND gate ic together with the +15V.
 

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Stuart

Jan 24, 2013
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Thanks for all of your help guys!

I've been working on it the past few days and I think I have finally cracked it, I'm almost there. So far my LED's light up in a chaser fashion, all I need for it to do now is to get it to stop at a random LED and stay lit.

For anyone who is interested here is my schematic.

51tvcx.jpg


The LED's light up on the top chip going from pins 00, 01, 02, 03 ect to 09 then the chip below does the same thing. Obviously when simulated the LED's don't light up in the correct order but this doesn't matter as long as I put them in the right order on my PCB.

Edit: (The two LED's in series in the 555 timer part of the circuit I have put there as a way of testing the 555 timer is working correctly, when the switch is closed the LED's should flash, just an extra feature I thought would be good for my design)


Edit:(Again): Turns out I was incorrect, my design actually works it is not just a chaser circuit haha, when I simulate it the capacitor just takes a long time to discharge and I didn't realize it was actually slowing down haha

Stu
 
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