Need some help on 555 timer...

Discussion in 'The Projects Forum' started by Hibaki, Dec 17, 2010.

1. Hibaki Thread Starter New Member

Nov 15, 2010
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Hi everyone.
Our group project is to make a counter counts to 7,stop the count and delay it for 1.5 secs before it can count again. but the problem is I am unable to figure out the connections from the counter to the 555 timer....pls help...

Also, our lecturers told us we will be using a 555 timer for this.

May 17, 2010
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3. Wendy Moderator

Mar 24, 2008
20,772
2,540
I'm one of the guys around here that is pretty handy with a 555. The counter is the hard part, have you done any work on it?

How many digits is the counter?

Power supply voltage?

Does a 555 generate the pulses that are counted?

Does a second 555 turn on and off the counter? Note: at this point the counter sounds very similar to a frequency counter.

Does the second 555 reset the counter to zero during the 1.5 seconds the counter is idle?

There will be more, but this is a start.

LEDs, 555s, Flashers, and Light Chasers

The 555 Projects

My Cookbook

555 / 556 Cookbook

4. Hibaki Thread Starter New Member

Nov 15, 2010
5
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1)single digit
2)5V
3)Nope. we use an ac to generate the pulses
4)so we need a 2nd 555 timer 0.0?
5)yes

5. Wendy Moderator

Mar 24, 2008
20,772
2,540
OK, so do you have a schematic of this single digit counter yet? It was the first question phrased differently.

We need information where the AC is coming from. Remember, we have no clue where you are, so if this is coming from your AC line current we don't know the frequency.

Basically you need a simple 555 oscillator feeding a OR or NOR gate (which is a AND gate with inverters in front) allowing your pulses to go through. The low duration of this oscillator is timed to let 7 pulses from your AC through, the high part of the pulse is to meet the 1.5 second requirement stated.

So as a hypothetical (for a 50 Hz signal) T2 = 140ms, and T1 = 1.5 seconds.

You are using an AND gate to the counter. Since the 555 signal is inverted for an and gate this becomes a OR gate.

Last edited: Dec 17, 2010
6. Hibaki Thread Starter New Member

Nov 15, 2010
5
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The counter i am using is the binary counter... and to add on, my counter shld not start counting again after the reset... so is it possible?
And is the mode of the 555 in monostable mode?

I think i need to sort out this problems before showing the diagram.

Last edited: Dec 19, 2010
7. KMoffett AAC Fanatic!

Dec 19, 2007
2,586
234
Hibaki,

I think you need to show us the diagram of the counter you are now using (or considering), before anyone can tell you how to add features with a 555. Please post your schematic or link.

ken

8. Hibaki Thread Starter New Member

Nov 15, 2010
5
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This is the counter without any 555 timer

Last edited: Dec 20, 2010
9. Wendy Moderator

Mar 24, 2008
20,772
2,540
After seeing the schematic another way comes to mind. A simple 3 input AND (I'd use a diode gate) feeding into a monostable that was set for 1.5 seconds. Much less tweaking required.

10. Hibaki Thread Starter New Member

Nov 15, 2010
5
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Thanks alot!!

Mind if i ask this, the 3 inputs are from the counter?(LSB to MSB)

11. Wendy Moderator

Mar 24, 2008
20,772
2,540
Doesn't matter, it a palandrome.

111 is the same way both ways.