ljcox

I have just realised what your problem must be.

Your drawing shows a connection between pins 1 & 12 of U1.

Is this connection really there? If it is, check if it is a good connection, ie. inspect it visually and, if it looks OK, measure the resistance between pins 1 & 12; it should be a low resistance, ie. < 1 Ohm.

If these pins are not connected then you will experience what you have described since the Modulo 5 counter won't be being driven by the Flip Flop, ie. only the flip flop will be changing.

In other words, Qa (pin 12) must be connected to input B (pin 1)

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Len

cannibal

WOW WOW WOW WOW WOW

finaly the counter is counting perfectly

0,1,2,3,4,5,6,7,8,9

the breadbord hole where wire of pin1 to pin12 was defected
I used another hole in the breadboard to connect pin1 to pin 12

and thats it

counting with no problems

thank you very much ljcox
also BIG thanks goes to audioguru and all other members who'ed helped me

all the best

ljcox

You're welcome. I'm glad that we were able to help.

It looks like you need more experience at fault finding.

The general principles are:-

Do a visual inspection and look for bad connections, short circuits, etc. and if any joints are soldered, check for dry joints.

If that does not resolve the problem, make voltage measurements. In your case, you would have measured a different voltage on pins 1 and 12.

If pin 12 was high, you would have seen a low on pin 1. So therefore there must not be a connection between them. Note that if pin 12 was low, pin 1 would also be low and therefore you would not know that the connection was faulty. So you need to change the state of the counter to check both cases.

If you have a multimeter with a continuity function, you can check for continuity between points that are purposed to be joined. So if you put one probe on pin 1 and the other on pin 12, there would have been no continuity.

Finally, when I am building something, I check the components before I insert them. New components are rarely faulty, but if one is and you don't check it, then having to fault find when the construction is finished can waste time.

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Len

cannibal

Thanks for the tips

Is it possible to make it count to 99?

and how the connections can be done?
by the way I decided to use power supply rather then 9V battery

audioguru

Of course. But most modern circuits use a microcontroller or Cmos ICs.
I haven't used old TTL since about 1972 when I started using Cmos instead.

Look in Google for Two Digit Counter Circuit.

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Uncle $crooge

cannibal

Done

pin14 of 74LS90 from circuit2 goes to pin 6 of 74LS47 from circuit1