here is a pic showing that sometimes 8 are goinig out and only led "8" is on and sometimes it's not the case..is there any chance that the Q where the led is driven have something wrong inside the ic???? my it be the case? also for the ones coming in All leds are working well and a 1k resistor is used in the schmitt trigger

 

Your battery was 6V when it was new. It is probably less than 6V now. Measure it while it powers your circuit.

Of course the resistor from the input of the Schmitt trigger through the switch to ground must be 330 ohms as is shown with Ohm's Law. If it is higher than 330 ohms then some 7414 ICs will not work.

The Schmitt trigger is not a "denouncing" circuit. Instead it is a "debouncing" circuit that prevents contacts bouncing in the switch from being counted as many pulses.

 

Please stop sending personal messages. Continue talking about your circuit in the forum.

I am glad to hear that adding a 10uF supply decoupling capacitor fixed your problems.
ALL electronic circuits need supply decoupling capacitors.

EACH TTL IC needs its own 0.1uF supply decoupling capacitor.

TTL circuits ALWAYS need a 5V regulator. A battery voltage jumps up and down as the load current changes. A TTL output draws a lot of current for a moment each time it switches and the LED display uses various amounts of current.

Your 6V battery drops to 4V or less as it is used. So buy a 9VDC wall-wart and make a regulated 5V supply with a regulator IC plus two capacitors. If you miust use a battery then use 7 AA alkaline cells in series to make 10.5V when they are new or make 7V when they are old. 7V is the minimum input for an ordinary 5V regulator.

 

Please stop sending personal messages. Continue talking about your circuit in the forum.

I am glad to hear that adding a 10uF supply decoupling capacitor fixed your problems.
ALL electronic circuits need supply decoupling capacitors.

EACH TTL IC needs its own 0.1uF supply decoupling capacitor.

TTL circuits ALWAYS need a 5V regulator. A battery voltage jumps up and down as the load current changes. A TTL output draws a lot of current for a moment each time it switches and the LED display uses various amounts of current.

Your 6V battery drops to 4V or less as it is used. So buy a 9VDC wall-wart and make a regulated 5V supply with a regulator IC plus two capacitors. If you miust use a battery then use 7 AA alkaline cells in series to make 10.5V when they are new or make 7V when they are old. 7V is the minimum input for an ordinary 5V regulator.

NOW sometimes the going when 8 are out only 8 lights up and sometimes 4 and 8 light up.

the 10 microfarad supply decoupling capacitor must be connected to the main vcc/ground rail or not, if not where it should be connected plz reply to that question specifically

 

You are doing a whole bunch of things wrong.
1. You must use 5V supply, not 6V.
2. Remove any capacitors between CLOCK and GROUND.
3. Put 0.1μF capacitors between Vcc and GND of each chip.
4. Put one 10μF-100μF between Vcc and GND.
5. It is not a good idea to drive LEDs from the same outputs that also drive the next clock. Use the unused Q' output instead.
6. You don't need those 10kΩ pullups. Connect the pushbutton across the capacitor.

How many have you done as suggested by MrChips ?

Did you do item #5?

From the datasheet of 7476, you can see that the output of 7476 can sink 16mA but can only source 0.4mA. If you connect the LED to GND through a 330 ohm resistor it is sourcing current from the "Q" output of 7476 and it will pull down the voltage when the output is at logic "H". That's why it is better to use "/Q" to light the LED, so the next stage's "clock" input can get an undisturbed logic "H".

Allen

 

How many have you done as suggested by MrChips ?

Did you do item #5?

From the datasheet of 7476, you can see that the output of 7476 can sink 16mA but can only source 0.4mA. If you connect the LED to GND through a 330 ohm resistor it is sourcing current from the "Q" output of 7476 and it will pull down the voltage when the output is at logic "H". That's why it is better to use "/Q" to light the LED, so the next stage's "clock" input can get an undisturbed logic "H".

Allen

What is the difference between the huge 100micro Farad and the small 100microfarad caps? and why did u use in a certain place a huge one an in other places a small one..thanks

 

What is the difference between the huge 100micro Farad and the small 100microfarad caps?

What is huge 100micro Farad and small 100micro Farad?

Allen

 

What is huge 100micro Farad and small 100micro Farad?

Allen

no i didn't mean that.. why in some places he used a bigg 100microfarad and in other paces he used a small 100nanofarad big by its size not capacitance.
see the circuit he done and see the picture i''ll attach

absf's circuit will make people come out not come in since when the clock is high Q will become high and Q' will become low then it will let people leave not people come in..and when i connected a 7447 already 1 guy is inside and that is not why we want..

 

Did you read this on the sticky?

http://forum.allaboutcircuits.com/showthread.php?t=45583

As for "Why electrolytic and ceramic in parallel?": Electrolytics have high storage capacity for their size, but this comes at the cost of higher Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL). These are the same parasitic elements of the circuit board we are adding the capacitor to correct! Hence, the mica or <insert dielectric here> cap that has nearly zero ESL and extremely low ESR. The smaller cap is able to supply the needed current instantly to "cover the gap" until the Electrolytic can "fill the gap" until the power supply finally "catches up" after a switching operation in a large logic IC, which uses a lot of current, relatively.

The other way of looking at these capacitors is as mathematical models, essentially broadband filters to "bypass" any ripple directly to ground.

Allen

 

Did you read this on the sticky?

http://forum.allaboutcircuits.com/showthread.php?t=45583



Allen

So basically i need 1 100microfarad between the main rail. in my board i'm a little bit confused where to put that 100nanofarad capacitor and do i really need them? i'll be connecting 0.1 micro ceramic betwenn vcc/ground of evry ic..why is that 100nf needed? and where do i need to connect it to make an effect on the diode?

 

When the output of an old TTL IC switches from high to low or from low to high then it draws a high current pulse from the power supply. If the IC does not have a 0.1uF ceramic supply decoupling capacitor to provide that current then the supply voltage to the IC will sag and the IC will not work properly. Especially with your tangle of wires all over the place. The 0.1uF ceramic capacitor should be as close as possible to the supply pins of the IC which is almost impossible on a breadboard.

 

When the output of an old TTL IC switches from high to low or from low to high then it draws a high current pulse from the power supply. If the IC does not have a 0.1uF ceramic supply decoupling capacitor to provide that current then the supply voltage to the IC will sag and the IC will not work properly. Especially with your tangle of wires all over the place. The 0.1uF ceramic capacitor should be as close as possible to the supply pins of the IC which is almost impossible on a breadboard.

Alright now I got it I will be using a 6v(4*1.5v) Battery and a voltage regulator that regulates my voltage to 5v now for the Supply decoupling will a 10microfarad serve me good for both the regulator and the main supply rail or going with a 100micro is better??Regards

 

Put the 10μF capacitor on the 5V side of the regulator.
Put the 100μF cap on the battery side of the regulator.

 

Put the 10μF capacitor on the 5V side of the regulator.
Put the 100μF cap on the battery side of the regulator.

Okay so..all the ideas are clear..but is a 100Microfarad a little big for a 6v supply?(since I'll be using a 6v supply) and if 100 is not suitable which is the value of the cap I have to connect to the 6v?
Regards

 

Why do you think it is too big?

 

Alright now I got it I will be using a 6v(4*1.5v) Battery and a voltage regulator that regulates my voltage to 5v now for the Supply decoupling will a 10microfarad serve me good for both the regulator and the main supply rail or going with a 100micro is better??Regards

No.
Your "6V" battery will quickly drop to only 4V and an ordinary 5V regulator needs an input of at least 7V. Feed an ordinary 5V regulator with 7 AA alkaline cells (10.5V when new and 7V when old).
Since old TTL ICs use a lot of current then the battery will not last long and the regulator will get hot and will need a heastsink.

If the regulator is on the same pcb as the circuit then a single 10uf output capacitor will also serve the circuit plus a 0.1uF (100nF) ceramic cap for each old TTL IC.

 

No.
Your "6V" battery will quickly drop to only 4V and an ordinary 5V regulator needs an input of at least 7V. Feed an ordinary 5V regulator with 7 AA alkaline cells (10.5V when new and 7V when old).
Since old TTL ICs use a lot of current then the battery will not last long and the regulator will get hot and will need a heastsink.

If the regulator is on the same pcb as the circuit then a single 10uf output capacitor will also serve the circuit plus a 0.1uF (100nF) ceramic cap for each old TTL IC.

The regulator is going to be in another board not on the same board of the circuit and then I'll give the 5 v regulated output to the rest of the circuit.. If using this configuration I'll be using 100micro on the battery side 10micro on the 5v regulated side plus another 100micro on the main rail vcc/ground of the circuit plus 0.1micro ceramic on each TTL and I'll be using a 12v single battery..can this work?

 

With a 12V battery the regulator will have 7V from input to output. The 7V times the current equals a lot of heat. The heatsink for the regulator must be big enough to cool it.

 

With a 12V battery the regulator will have 7V from input to output. The 7V times the current equals a lot of heat. The heatsink for the regulator must be big enough to cool it.

12v will to be good? I'll be using a 12v On the 12v input I'll connect a 100micro and on the 5 regulated I'll connect 10 micro and I'll connect a 100 micro on the main rail(vcc/ground) and 0.1 micro for every TTL chip can I do that? Will it work? Just answer me yes or no...regards
Omar

 

I've looked on the lm7805a regulator datasheet for fixed output regulator.
On the datasheet for input 10v output current 1A
The capacitor on the 10v side must be 0.33 micro and on the output 0.1 micro..are these ceramic ones it's not specified on the datasheet
again these values are for 10vi. What are the values I have to put for the caps
For a 12vinput ?? See page 12

http://http://www.fairchildsemi.com/ds/LM/LM7805.pdf