Counter circuit refuse to count- HELP!

Status
Not open for further replies.
F

folarinv

New Member
I constructed a counter circuit with: 555(astable-pulse generator), cd40192-decade counter, cd4511(bcd/7-segment driver) and 1 section of a double 7-segment LED display. The problem is that the counter sometimes sits down at zero and refuse to count up and atimes it would randomly display figures that does not correspond with the original count (i.e it displays: 7, 2, 5, b and inverted b).

I used a separate LED to monitor the pulse from the 555.

cd4026
cd4033
cd40162
are all difficult to source from the local market in my resident town.
 
Maybe you might want different chip numbers.

Get a 4-bit binary counter, and get a common BCD to 7-segment display decoder. Look for chips ending in 47, or 247 for the decoders.

Connect the address lines of the decoder to the correct address lines of the binary counter.

Now hook up the output of the 4th bit to either an inverter or to the RESET pin depending on whether the RESET requires an inverted signal or not. When everything works, you will see numbers 0 to 7 in order, and the process repeats.
 
mstechca said:
Get a 4-bit binary counter, and get a common BCD to 7-segment display decoder. Look for chips ending in 47, or 247 for the decoders.
Click to expand...

Do you know the difference between a binary counter and a decade counter when it is used it to drive BCD-7segment display decoder?

Why would someone want to count from 0-7 only? Does the OP said he want to do just that?
 
You cannot leave any unused inputs of CMOS floating. For the 192 load and clock down high, data inputs high or low
The problem is that the counter sometimes sits down at zero and refuse to count up and atimes it would randomly display figures that does not correspond with the original count (i.e it displays: 7, 2, 5, b and inverted b).
Click to expand...
Since the 4511 does not display invalid codes the b may be faulty connection to 7 seg display.
 
folarinv said:
The problem is that the counter sometimes sits down at zero and refuse to count up and atimes it would randomly display figures that does not correspond with the original count (i.e it displays: 7, 2, 5, b and inverted b).
Click to expand...

Did you connect a bypass capacitor across the supply (ie. from Vdd to Vss) close to the counter IC?

If not, this will explain the random results. When CMOS ICs change state they cause a current pulse in the supply line. If there is no bypass caps to smooth this, it can cause odd behaviour simlar to what you have described.

A 100 nF ceramic capacitor across each counter IC should be sufficient.

Also, as FRIED said, unused inputs must be connected to Vss or Vdd.

Len
 
Hi Len,
How many hundreds of mA is the ordinary high power 555 oscillator sucking from the supply when its output switches? :lol:
 
The spike is very high according to the following website.

Quote:
====
When the output of the 555 makes a transition, there is a large current spike in the supply current, up to 300 or 400 mA for a short period.

**broken link removed**

End quote;
 

I know the difference.

The reason why I said that is because the 7 segment decoder takes 4 bits as input and a 4 bit binary counter can only output 4 bits. It will still show the weird characters, but at least the numbers are in order, and all the OP has to do is grab the code for the last digit (1001 or 9) and force a reset on the counter when the number is reached. a 2-input AND gate will do the trick.
 
mstechca said:
... and all the OP has to do is grab the code for the last digit (1001 or 9) and force a reset on the counter when the number is reached. a 2-input AND gate will do the trick.
Click to expand...

You said you know the difference. Does a decade counter needs an AND gate to do the reset trick?

You are advising others to use a binary counter with an AND gate in which a decade counter will do just fine without, is there a reason for that?
 

I'm puzzled. Why use a binary counter when a decade one would do without the need for an AND gate? Incidentally, the AND gate would have to detect 1010 not 1001 if you want it to reset at the tenth pulse. ie. count from 0 to 9.

Len
 
mstechca wrote:
The reason why I said that is because the 7 segment decoder takes 4 bits as input and a 4 bit binary counter can only output 4 bits.
Click to expand...
Well I guess Decade counter also outputs only 4 bits
Dont you guys think this topic has gone off the course
The person who posted the topic has not replied even once so nobody exactly knows what his problem is/was?
But every body here is assuming different fault conditions which I think will be good for a newbee to read
 
We are letting Murphy's Law run amuk by discussing anything and everything that can foul a counter. :lol:
 
Re: try looking off this

Tom McCurdy said:
https://www.electro-tech-online.com/threads/i-need-help-in-designing-a-circuit.16241/#post-92915

its is a working circuit i made of a counter....

**broken link removed**
Click to expand...


The counter circuit is working fine now. I used 7490 and 7448 and connect the pins as you have advised. the problem I had b/4 was that I did not connect input-B to output-A on the counter and I left some input pins unconnected.

Thanks everybody! all the suggestions were helpful.
 
Re: try looking off this

Tom McCurdy said:
https://www.electro-tech-online.com/threads/i-need-help-in-designing-a-circuit.16241/#post-92915

its is a working circuit i made of a counter....

**broken link removed**
Click to expand...


The counter circuit is working fine now. I used 7490 and 7448 and connect the pins as you have advised. the problem I had b/4 was that I did not connect input-B to output-A on the counter and I left some input pins unconnected.

Thanks everybody! all the suggestions were helpful.
 
Re: try looking off this

Tom McCurdy said:
https://www.electro-tech-online.com/threads/i-need-help-in-designing-a-circuit.16241/#post-92915

its is a working circuit i made of a counter....

**broken link removed**
Click to expand...


The counter circuit is working fine now. I used 7490 and 7448 and connect the pins as you have advised. the problem I had b/4 was that I did not connect input-B to output-A on the counter and I left some input pins unconnected.

Thanks everybody! all the suggestions were helpful.
 
Good old TTL saved the day!

Summary:
Counters work best when they are hooked-up properly.
Cmos logic works best when all its inputs are terminated.
The ordinary old 555 "bleeps" a huge supply current spike when its powerful output switches. :lol:
 
Status
Not open for further replies.

Similar threads

V
  • Question
High voltage detection counter
Replies
16
Views
4K
vortex0606
V
T
  • Question
4029 and 4511, 2 digit up down counter
Replies
1
Views
2K
sarahMCML
S
J
  • Question
A circuit to block back-feeding to another line
Replies
15
Views
5K
Nigel Goodwin
  • Question
Help with boost converter circuit
2
Replies
25
Views
5K
audioguru
S
  • Question
Need help with spst toggle to momentary
Replies
5
Views
3K
crutschow
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…